New Long Range Pattern Setting Up

After reviewing the ensemble runs of the GFS and Euro model, as well as looking at teleconnection forecasts, I can see that there is going to be a MAJOR shift in the storm track over the next several weeks.

First of all, the NAO, which is the North Atlantic Oscillation, will transition to its positive phase this week, after being strongly negative for almost two months. This is a significant trend, and may not be a good trend for a cold winter across the area. The positive phase features a ridge centered on, or just off of the East Coast. "Coupling" with this positive phase of the NAO, will be the PNA, which is the Pacific North American index. The PNA will likely be in its negative phase at the same time the NAO will be in its positive phase, likely resulting in a strong West Coast trough. Another teleconnection I am watching is the AO, which is very similar to the NAO, but it is determined by the arctic stratospheric circulation. In this case, when the AO is in its positive phase, which it will be for the next few weeks, a strong jet stream results over North America, especially in occurence with a negative PNA and positive NAO pattern. Last winter, a positive NAO in combination with a neutral AO allowed for a split flow jet stream. With this upcoming weather pattern for most of November, a strong jet stream will be in place across the country, allowing for occasional strong storm systems to traverse the nation, the first one being this weekend and early next week, which will bring a wave of showers and thunderstorms to the area. Most of these storm systems will likely cause brief warm ups, which will bring periods of rain to the area. After these storm systems pass through, transient cold waves will move into the area, bringing periods of well below normal temperatures. This type of a weather pattern most reflects November 2010. In fact, I believe that this could be a positive factor in cold, snowy conditions across the U.S. this year (unlike last year).

In my opinion, this indicates that the Midwest is about to get quite a bit stormier, with frequent storm systems bringing the chance for snowstorms across the Upper Midwest, and severe weather outbreaks in the Central Plains to the Ohio Valley.

GFS ensembles indicate a strong Pacific jet stream in the long range, including a strong West Coast trough.

In all, expect this: The pattern will transition from a blocked, slow upper level wave pattern, to a transient (including a strong Pacific jet stream), highly variable weather pattern, including periods of warm and cold weather. Ultimately, this is a bit different from last year. Last year, blocking was in place, it just set up in the wrong places.. I believe that this fall and winter will most likely resemble the fall and winter of 2010. Do not be discouraged with warm patterns, because it is likely that a cold pattern will follow. Follow Northwest Ohio Storm Prediction Center for more information on the upcoming weather pattern.

Intense and Powerful Storm System Coming Onshore

As you may have heard on the news, a "historic" and "record-breaking" low pressure system will move onshore later tonight near the Delaware River in Southern New Jersey. There are many things that will make this system a literal "Storm of the Century". It's central pressure at landfall (it will have completed the transition to an extratropical cyclone) will be around 935 millibars, which would break ALL pressure records in the contiguous United States and quite possibly the ENTIRE United States. Also, it will be incredibly large. In fact, it surpassed Hurricane Igor as being the LARGEST hurricane on record, with a tropical storm force wind field 1000 miles in diameter! The hurricane force wind field is about 175 miles in radius, which is nearly double Hurricane Katrina's hurricane force wind field. The large wind field in combination with an extremely low pressure will create a massive storm surge along the East Coast, mainly near Delaware to New York City, where a surge of nearly 15 feet is possible. Also, since this storm will be transitioning into an extratropical low, it's wind field will only increase in size, to the point where our area will receive wind gusts up to 55 mph today, and possibly 60-65 mph tonight into tomorrow morning!

As for precipitation in our area, I'm expecting nearly an inch of precipitation from this storm, with precipitation occurring throughout the days Tuesday and Wednesday. One interesting thing though is that forecast soundings do support a steady snow from the overnight hours Monday night and Tuesday through mid-morning hours. This mainly goes for Northwest Ohio, which will be closer to the source of lift, and in cooler conditions. During this period of snow, sleet and rain could mix in. By noon, most of the precipitation will have changed to rain, and will continue as rain through Wednesday night.

I will have another update either late tonight on the facebook page or tomorrow morning on the blog. Stay safe!

Implications of Today's Model Runs.

After a rather depressing few runs the last few days (in terms of a big storm for parts of the East), ALL of the major global models, and even regional models are beginning to agree on the track, and even the intensity of this hurricane/hybrid storm. I am NO longer considering a solution that sends the storm out to sea, as this is very unreasonable given the current weather pattern.

In fact, the models have trended nearly 2000 miles west of the original storm tracks since yesterday. This is a MAJOR improvement over the last past several model runs. With this in mind, I expect a continuing westward trend until about Friday, when the models should begin to agree on the general storm track. Right now, the ensembles are even more reasonable with this storm, putting it much farther west than even the operational runs.

With all of this talk of the models, here is the reasoning and set up for this likely major and potentially devastating storm system.

Currently, and as we speak, Hurricane Sandy is rapidly intensifying in the Caribbean Sea, just south of Cuba. Just yesterday, it was named Sandy, so as you can see, this is a HUGE jump in intensity. Satellite imagery shows a well-developed eye forming in the center of the storm, along with a "stadium" like eye, usually indicative of rapid strengthening. I would not be surprised in the least bit if Sandy becomes a major hurricane before hitting Cuba tomorrow. Given the current slow storm movement, this seems extremely likely.

Another factor that will likely be in play is a giant West Coast long wave trough. A strong ridge will begin to push this trough out of the West, sending a cold front through our area Thursday night and Friday, along with widespread post-frontal rain, making for a rather gloomy day Friday. It is VERY important to track the strength of the trough, and its movement, as this will determine the strength and track of the hybrid storm once all of these come together.

A third and final factor in this "superstorm" of sorts is a mega North Atlantic blocking pattern. This ridge will get completely in the way of this storm's progress north. My theory is that it will have only one way to go once it gets "locked" into the upper level trough (previously mentioned), and that is straight west and a direct hit on the East Coast. The strength and position of the strongest blocking will determine the path of the storm as well.

Here's what I believe will happen: The hurricane will move due north through the Bahamas, maintaining hurricane status throughout (or just slightly below hurricane status). Once it re-emerges into the Gulf stream region east of Florida, it will likely strengthen, not only due to warmer waters, but because it will begin to "phase" with the upper level trough, providing energy and sustaining the storm. Depending on the degree of phasing (which at this time I believe will be strong), the now hybrid Sandy will continue moving north, and once it reaches around the Chesapeake Bay, it will make a likely sharp turn west, making landfall on the New Jersey coast. The storm system will continue to rapidly strengthen as it transitions to a baroclinic storm, and the upper level system will guide it west. Here's the problem for our area. A few models and ensembles are indicating that the storm will move far enough west to hit our area with very strong winds, and quite possibly SNOW. This is not set in stone in the least bit, but this is one of the more likely solutions. If the storm does move far enough west, we could have some adverse impacts from the storm, ranging from precipitation and wind.

At this point, I'm going to continue to watch. The most consistent and probably most accurate models are so far the NOGAPS and ECMWF. The GFS has not been consistent and is now considering a storm that moves out to sea and doesn't even affect the East Coast. The bottomline is this: The East Coast, if impacted by this storm, could be devastated, with widespread flooding and wind damage likely.

I'll continue to update the blog regarding forecasts on this storm.

Storm lingers on Horizon. Model Mayhem ensues.

After monitoring weather models for several days now, we have begun the model mayhem with this storm. Originally, the entire storm was expected to move inland by most models. Now, some are taking it out to sea, and others are taking it along the coast, and some are taking it inland. Everything has been rather crazy lately with this storm. I am really concerned about the potential impacts due to the sheer size and intensity that is forecast of the storm. For now, all I can say is that models are now trending back westward to an inland solution, which puts the area back under the gun for the possibility of inclement weather early next week. At this point, it is all I can say. Tomorrow, I will post an update about the physics behind the storm, and how it will likely develop.

Ice Crystal and Snowfall Formation (Continued...)

In the past article, I mainly explained how ice crystals and precipitation forms in warm core and cold core clouds. In this article, I will be explaining what conditions are necessary for snow growth. I will explain the temperatures and humidity levels that are needed for snowfall.

Let me start where I left off in the last article. Most precipitation in the mid-latitude regions results from the growth of ice crystals in the glaciated, and "mixed" (region of the cloud that contains both cloud droplets and ice crystals) regions of the cloud layer. The mixed region of the cloud always occurs from about the freezing level to -40 degrees Celsius. The glaciated part of the cloud will always occur above -40 degrees Celsius. But this is for spring and summer clouds, where temperature are very warm in the low levels. During the winter, clouds are made up of predominately ice crystals and water droplets, which tends to make them higher above the earth's surface. The cloud droplets that do make up at the cloud at it's lower levels are very tiny. Due to the lattice structure of an ice crystal, it loses very little water to evaporation. What this means is that vapor pressure is less around an ice crystal than it is around a cloud droplet (which means that when the air is saturated over an ice crystal, it is supersaturated over a water droplet, above 100% relative humidity). The vapor pressure "gradient" causes water vapor molecules to move from the water droplet to the ice crystal, and depositing on the crystal causing it grow. In this way, since the ice crystals are in relatively less abundance than are water droplets, they grow at the expense of the massive amounts of water, and continue on the process as they shatter. Eventually, if the thermodynamic profiles favor it, the shattered ice crystals will attach themselves to another ice crystal, and fall to the earth as a snowflake. The snowflake will only reach the earth's surface if the entire temperature profile is below or right near freezing temperatures. In the next section, I will talk about the required conditions for snow crystal growth.

In order for snow crystals to grow most rapidly at the expense of the water droplets around them, certain temperatures are required. In the field of cloud physics, much research has been achieved on the required temperatures for the most rapid snow growth. In most research experiments, it was found that dendrites (the most efficient type of ice crystal) that grow from accretion and deposition grow in the areas of the cloud that are in between -10 and -18 degrees Celsius (14 degrees Fahrenheit to 0 degrees Fahrenheit). These dendrites have the shape of a prism with a hexagonal shape. This is not the only condition that needs to be met for the most efficient snow growth. Another condition includes a relative humidity that is near or over 100%, which will allow the ice crystals to maximize growth. It also helps the situation when strong upper level lift is located in the same thermal layer.

Dendrites are not the only way snow can form. Other types include rimed ice, platelets, and the traditional snowflake. Rimed ice crystals usually form when the precipitation layer has temperatures near or around -4 to -6 degrees Celsius. In this case, the ice crystals tend to be very wet, and allow for a better surface for water to "stick" to. These are the very wet, and large snowflakes that we occasionally see during the late winter and late fall months. Platelets are another type of snow crystal, which are usually very, very small. They tend to form during the coldest winter patterns (namely cold lake effect snow events), where cloud temperatures are below -25 degrees Celsius. They create the sight in the air that makes it look foggy. They are usually the snow crystals that blow very easily, and are the main reasons for visibility problems during winter storms. On the otherhand, the traditional snow flake usually forms in relatively warm cloud conditions; Colder than with rimed ice crystals, but warmer than dendritic snowflake conditions. They can easily become bigger, but water vapor does not stick to them as well. Normally, snow events dominated by these type of crystals do not usually bring much accumulation (but it is possible).

Next week, I will be writing an article about the myths in the Arctic, mainly about Arctic sea ice extent, actual observed temperatures, and winter/summer time weather.

Yet Another Impressive Storm System on the Horizon.

By now, most of you are probably tired of the extreme weather we have been experiencing so far this fall. From extremely high winds and heavy rain, to chilly, freezing nights. We've had days where it was nearly 80 and the next day, it was in the 40's.

Well.. I'm here to announce that yet again, another extreme weather pattern is coming. This one looks to be quite violent too. This time it will be quite different from what we've usually seen this fall. The new pattern involves a tropical cyclone, a large West Coast trough, and unusually warm conditions over the North Atlantic.

Now to explain what's going on. Over the weekend, the trough that brought the chilly weather Thursday and Friday has moved off to the East over Maritime Canada. In the wake of this trough, a major warm up will ensue. Upper level ridging will build into the area, resulting in temperatures approaching 80 by midweek, under mostly sunny skies. Thursday night and Friday, the western trough splits, sending a shortwave eastward, which will deepen rapidly, cause the development of a large surface storm, and send a cold front eastward, approaching the area. This cold front will slide through the area, with some post-frontal rain.. Mainly a few showers and possibly a thunderstorm. Friday looks fairly dry, but cooler, under mostly cloudy skies with highs in the upper 50's. This is where everything gets interesting.. Depending on the timing of a deepening upper level trough, an incredibly strong storm system will affect the East Coast. This storm will not be ordinary in anyway.. In fact, it will likely be a hybrid storm of sorts. The surface cyclone that will develop in response to the upper level trough will phase with a tropical cyclone that will be strengthening along the west coast of Florida. The strengthening trough will likely draw the storm northward. Here's the problem, at this time, nothing is set in stone of when this storm will likely hit the region. In fact, some of the models are having the storm stall out along the East Coast and move northwest towards Michigan! And some of them are bringing the storm out to sea after Sunday. Looking at the 12z GFS, it is expecting the entire storm to impact the region with some gusty winds, and possibly a rain/snow mix (but the latest runs are suggesting that it is moving towards a warmer solution).  The 12z CMC and ECMWF are both expecting a rapidly deepening storm (this is what the NWS expects), with very cold air wrapping around the southwest side of the storm (where we are going to be at), and they are both expecting the storm to make landfall on the East Coast and travel up the Great Lakes. Most likely, the storm should hit around the Sunday-Monday-Tuesday timeframe (I don't agree with the NWS's forecast of the storm impacting us Saturday night, that is way too early for this tropical system to develop).  If the ECMWF and CMC are correct, expect rather cold temperatures for Saturday-through at least Tuesday. Highs will likely only make it as high as the middle 40's. Another interesting thing that both models are forecasting is high winds. The ECMWF is forecasting wind speeds of over 60 mph! Again, you have to remember that this is a hybrid tropical/extratropical cyclone, so not only will it bring cold air, but also high winds.

The one interesting thing that I saw on the ECMWF model, and NWS forecast discussions, is the possibility of ACCUMULATING SNOWFALL from this system. In fact, some models are forecasting several inches of it. This is something that I will have to monitor, because it seems as if a wind-blown, heavy wet snow could be likely by next Sunday or Monday. Even though the air behind the system will be rather cold, it won't be cold enough to support snow during the day. The snow will likely occur during the night hours.

In any case, this could be a dangerous storm, not only for this area, but for most of the East Coast (due to the size of the storm, and its hurricane force wind speeds.) I will continue monitoring it throughout the week.

This model forecast clearly depicts a very strong storm system in the East.

Impressive Storm System Coming Together For Mid-Week

Currently, I am monitoring the development of a storm system on the computer models. This system looks rather impressive at this time, and I am expecting it to have a significant impact on the Northwest Ohio/Northeast Indiana/Southern Michigan weather... In fact, before its all said and done, we may see everything from heavy rain and high winds, to even some wet snow!

  

The Details

Right now, a strong jet streak is taking shape over the Eastern Pacific. By Tuesday and Wednesday, this jet streak will "roar" into the Western United States, causing a storm system to move on shore. At the same time, a weak trough will move southeastward out of Canada. The jet streak will deepen the trough rapidly. As the trough deepens, the storm system will begin to take shape at the surface, and deepening rapidly. What this means for us is strengthening winds again for Wednesday. While a pronounced warm up will affect the area, it will also bring high winds to the area. This system will be the factor that allows for extremes this week. For example, the storm system will cause temperatures to jump from the lower 50's today, to the low and middle 70's by Wednesday! And then, the strong cold front will cause temperatures to jump back to the lower 50's with a chilly rain for Thursday and Friday!

Rain will be likely Wednesday night as the cold front pushes through the area. Thursday, the jet streak will allow for the development of additional periods of rain across the area, causing a rather cool and wet day. By Friday, the core of the cold will move over the area, allowing temperatures to only hit near 50. Keep checking tomorrow for additional updates regarding his impressive storm system.

(For additional information regarding the storm system, I suggest visiting the NWS's website at National Weather Service and/or WLFI Weather Blogs. Also, try The Weather Channel's site for any other information)

After that, general model agreement suggests another pronounced warm up as the PNA (Pacific North American index, a way of measuring the jet stream patterns over the North and East Pacific) goes negative. This will lead to another crazy weather pattern, and if the ECMWF is correct, it could lead to another major storm system coming through. If the ECMWF is correct, it is suggesting that this will be on the leading edge of a major arctic wave, possibly bringing the first snowflakes of the season by the end of October and early November.

The NAM clearly depicts the incredible jet streak, which will be the main "perpetrator" in the development of this exciting storm system.

The jet streak then is forecasted to dive into the Midwest, causing the deepening of the storm system.

Ice crystal formation

Sooner than we would like it to be, winter is approaching quite quickly. We have already seen the first frosts and freezes. We have seen wild storm systems move through with heavy rain, high winds, severe weather, and basically any type of weather you can think of (except of course snow). Soon, it will begin to become much colder, and we will soon be thinking of the holidays, and of course snow. If you recall my winter forecast, I specifically stated that I expect this winter season to be much more exciting than last year... What this means is that I expect more storms, more snow, and more cold weather. This article and the next one will primarily be about cloud formation, the crystals that make up the ice crystals, and what causes them to form.
   Before a cloud can form, two primary conditions must be in place that influence the development of the cloud. The first condition is primarily "lift". When I say "lift", what I mean is the literal lifting of air vertically in the atmosphere. Due to the laws of thermodynamics, this body of air must cool. This leads to the second condition, which is moisture. Without moisture clouds cannot form. A body of air will always have a specific amount of moisture. As it moves up, this value changes little (except when it changes due to changes in pressure). When an air parcel cools as it is lifted, its temperature approaches its dew point temperature, the temperature at which condensation occurs. As the relative humidity approaches about 80%, water vapor begins to condense onto hygroscopic cloud nuclei. As the body of air is lifted further, and the relative humidity approaches 100%, and water vapor begins to condense onto even non-hygroscopic particles (for later reference, hygroscopic literally means "water attracting".) As the air is lifted further, the cloud builds upward, towards cooler and cooler air temperatures. Even though water freezes at 0 degrees Celsius, cloud droplets do not because there is no flat surface for to freeze to, therefore there are relatively little amounts of ice crystals around and just above the freezing level. As it progressively gets colder with height, more and more ice crystals are found. This can only be explained by the fact that not only do ice nuclei exist at these levels, but it is cold enough for some of the large droplets to attach to them. At this point, there is still an abundance of cloud droplets. At the -40 degrees Celsius level, that is the point at which water can directly freeze, in a process called deposition. No ice nuclei is needed, which allows water vapor to freeze directly with each other into crystalline shapes. Since this article deals directly with snow crystal formation, I will not talk about this much. This is because most winter storms do not have cloud temperatures below -40 degrees. So then, how do snow crystals form? Exactly as I stated in the first process; This is the one I will elaborate on.
   Ice nuclei are quite rare in our atmosphere compared with condensation nuclei. This can be explained by the fact that ice crystals need an exact crystalline structure to cause snowfall formation. There are very few particles that cause the freezing of water droplets in a crystal shape. Therefore, ice crystals have very little competition for available water. Once water begins to attach itself and freeze to the ice nuclei, vapor pressure around the ice nuclei decreases. Once the crystal forms a flattened, ice crystal structure, the differences in vapor pressure between the ice nuclei and cloud droplets (this means that if the air is saturated with respect to water, it is supersaturated with respect to ice) cause water vapor to "gather" near the ice nuclei (due to the freezing cold temperatures, water tends to congregate in certain areas), and attach themselves to it, also known as the process of deposition. Once several ice crystals have formed on ice nuclei, this sets up the conditions for the formation of new ice crystals. Ice crystals are quite a bit heavier than cloud droplets, and so they fall. Different fall speeds between ice crystals and cloud droplets (and other ice crystals) cause collisions, which shatter the original ice crystal. This sets up an opportunity for new ice crystals to grow, because water droplets will now attach themselves to the shattered fragments. These shattered fragments begin to grow at the expense of the water around them. This process describes how precipitation forms in cold core clouds (temperatures below freezing in the cloud), not just snow. Snowfall requires very precise conditions for formation. At this.. I will leave snowfall formation for the next article. One thing I can tell you though, is that there is a persistent myth about snow in society today. This myth is that snow can only fall when it is below freezing outside.. That is NOT true. And I will explain this in the next article. The next article will focus on winter storm precipitation processes, and how precise conditions have to be for snowfall.

Large Scale Pattern Change Possible.

This won't be as long as most long-range posts, so I'll make it quick and simple. Over the past few days, NCEP ensembles have continuously forecasted that a large scale pattern change is underway. Ongoing research suggests that Ensembles (a group of several model permutations that are either averaged for a mean value or to show the differences between the possible solutions, in which the permutation in the model forecast could be a change in the physical schemes, dynamical schemes, grid spacing, etc...) are notoriously better at forecasting long-range patterns than the actual operational models themselves. The ensembles that the National Centers for Environmental Prediction is using is forecasting a drastic and extreme change in the teleconnections. Usually, during a medium to long-range period, models forecast one or two of the "important" teleconnections (which include the AO, NAO, and PNA; Arctic Oscillation, North Atlantic Oscillation, and the Pacific North American index, respectively) to go negative or positive. This time, each variable will be correlating with each other, which has very serious implications for the latter half of October and beginning of November. They are forecasting the AO to go strongly negative, the NAO to go strongly negative, and the PNA to go strongly positive in the long-range period, which is a very good indicator that it is going to be very cold for the end of October and beginning of November. It also indicates that a very strong storm system may be in the making for medium range period, especially after the 20th of October. I will continue to monitor the situation, but as I have already stated, the ensembles have been very, very consistent on this issue.

For those who don't want a technical outlook, here's the main thing. By the end of October and early November, expect a very cold air mass to move into the region, quite possibly bringing the chance for our first snowflakes, and likely on the tail end of a monstrous storm system.

Light blue represents below normal temperatures and dark blue represents much below normal temperatures. This will likely take place anywhere in the timeframe from October 23-November 3.

Different Weather Pattern

Over the past several days, models have continued to indicate the arrival of a very cool air mass into the United States. For this to occur, several things must happen first. For one thing, the large upper level low over the lower Mississippi Valley and Deep South will be "kicked" out of the United States by a large upper level wave moving southward out of Canada and into the Northern Rockies. This upper level wave will deepen and cause the formation of a surface low pressure system along a developing strong baroclinic zone (temperature changing over a given distance or a temperature gradient). This low pressure system will move in a hook shape, first moving southeast into South Dakota, and then making a sharp turn to the northeast and moving into Minnesota and Canada. At the current time, models are forecasting that the air will be cool enough to cause a significant snowfall over Northern Minnesota and North Dakota. But that is another story. As for here, I expect that the storm system will drag a cold front through the area by Thursday night.. Ahead of the strong cold front, temperatures will warm into the upper 70's for Thursday afternoon. At the same time, it could get fairly breezy. Thursday night, the cold front will be strong enough to generate a few showers and possibly a thunderstorm with the available moisture. As the cold front passes, temperatures will drop rapidly and then remain steady in the lower 50's.. On Friday, lingering cloud cover and lake effect rain showers will keep temperatures below 60. For the weekend, a secondary cold front will move through the region, reinforcing the initial shot of cold air, and causing temperatures to drop again. This will cause another lake response, causing widespread cloud cover for Saturday and possibly Sunday. This will limit highs to the lower and middle 50's! In fact, conditions may be just cloudy and breezy enough to limit highs below 50, making for quite a chilly weekend. Both Saturday and Sunday night look to bring a high potential frost. In fact, if the wind is light enough and cloud cover is limited during the night, we could be seeing the first FREEZES of the season. This will be quite early for this area, and if realized could be one of the earliest in many years. In any case, I expect a widespread frost both Saturday and Sunday nights, and possibly Monday night.

After the weekend, model solutions diverge, with some models holding the cold air mass across the region, and some moving it away rather quickly. This will all depend on the transition of the longwave pattern. At this time, I would lean more towards the models that hold the cold air mass in the region, due to the strength of the blocking ridge of high pressure in the Gulf of Alaska. Time will tell, but the next several weeks look to be rather cool across the area.

Map of forecasted temperature anomalies.. As you can see, there is a large area of below normal temperatures across the Midwest and Great Lakes regions.

Some Interesting Implications...

After doing some more research.. There hasn't been much correlation between this year's ENSO phase and other years. I've been looking for years that correlated well with an ENSO neutral event after a "double dip" La Nina. So far, 1977-1978, and 2009-2010 come up.. There haven't been any other "double dippers" (I have not included the years from 1998-2001 because that wasn't really a double dip La Nina, more of a continuous one that got us going in the so far downward trend in the PDO) than these.. And I want to opt out and not include 2009-2010 because of the strength of the El Nino (at this point it isn't likely we see a strong El Nino). In fact, most of the atmospheric signals indicate that this El Nino won't even survive for the beginning of the winter.  An ENSO neutral winter occurring after a double dip La Nina has not occurred in the history of record keeping of the ENSO phase. At this point, if weather patterns were to be followed, then I would predict a moderate or strong El Nino by winter. If I were to follow other signals, then an neutral ENSO winter would be more likely. I have made a map that shows the average temperature anomaly of all the ENSO neutral winters that are on record.

This clearly indicates that most ENSO neutral winters featured below normal temperatures, especially across the Northern Plains.

At this point, I really don't want to say what this winter will bring. With its unique weather patterns and variables, I cannot accurately use analogues to predict the winter temperature, snowfall, or precipitation. At this point, I'm going to lean on the side of caution. Quite a bit of data would suggest that a colder than normal winter is coming for the U.S. Some data would suggest that we will receive a warmer winter. In the history records, there have been two years that came out of a true double dip La Nina into an ENSO neutral or weak El Nino year, and one year that came out of an elongated La Nina. The two years that became a weak El Nino after the "double dip" La Nina were extremely cold years. The year that became a weak La Nina winter after the elongated La Nina, featured warmer temperatures across the East and cooler conditions in the West. At this point, the weather patterns are most similar to that of the first set of years, which occurred after a "double dip" La Nina. This would indicate that this upcoming winter could feature the same. More data will have to come up to prove this, but it is a very possible scenario. The only reason that I won't confidently project the idea of a very cold winter is because of what happened last year. For a few weeks I will wait and see what will happen.

For some entertainment, here is a map providing the average temperature anomaly across the United States from the winters of 1977-1978 and 1976-1977..

Temperatures during those two winters averaged nearly 10 degrees below normal.. According to archives and other records, the two winters featured extreme arctic cold, and several notable blizzards and snowstorms.

Longer Range Forecast...

Some interesting developments have occurred in the longer range forecasts of the ECMWF and GFS. One of the main things that I look for in the models longer range forecast hours is the general upper level flow patterns. In the 240 hour timeframe, the ECMWF is forecasting the development of a large upper level trough as the ridge in the Gulf of Alaska restrengthens (suggesting to me that the Polar vortex will remain weaker through the long-range). This upper level trough will show up as a slightly negative PNA teleconnection in the forecasts. With this kind of a jet stream configuration, strong southwesterly flow in the upper atmosphere is likely over our area. This is a pattern favorable for storm systems to transverse the Midwest and Central Plains. In the longer-range, I would anticipate near normal precipitation, due to the fact that most of these storm systems will be diverted to the north and west of the area. So far, this is an atmospheric set up very similar to the fall of 2010. The rather warm fall of 2010 eventually gave way to the very stormy and cold winter of 2010-2011. One forecast doesn't mean anything, but if this is consistent, I would bet on seeing a winter across the United States that will be very similar to the winters of 2009-2010 and 2010-2011. In the meantime, what it means for us is that we will likely continue with a warmer than normal, with a possible slight re-strengthening of the current moderate drought conditions.

El Nino and Tomorrow's Forecast

To begin today's forecast and outlook, I will begin with another update regarding the long range forecast. The El Nino has severely weakened over the past few days and weeks. Now, while I do refer to this event as an El Nino, it is not officially an El Nino. To be considered a true ENSO event, the Sea surface temperatures relative to normal (on either side of the spectrum) across the Equatorial Pacific need to be at least 0.5 for an El Nino and -0.5 for La Nina. This condition needs to be true for at least three months. In this year's case, neither has happened. SST anomalies have not been consistently above 0.5 degrees Celsius, and they have not persisted for three months. In fact, in the latest analysis of the El Nino, most of the remaining warmer waters have faded and shifted westward, causing an extreme weakening of the El Nino. This could be really good news for anybody who loves a good winter in our area. Using climateology, "neutral" winters  usually give us the best chance for heavy snowfall events across the area. Hopefully, this is true, as last year was too warm to support any "real" snowstorms.
    
For tomorrow's forecast, I expect clouds to build into the region ahead of a shortwave. I expect a few showers and even a thunderstorm in the afternoon hours. Yet another small "storm system" will move south out of Canada, sideswipe the area with some rain on Wednesday. A short period of cooler temperatures will come to the area after the passage of the cold front, with highs dropping into the middle 60's on Thursday. For most of the week, I expect temperatures to remain right near 70. By the beginning of next week, signs are pointing to cooler weather across the United States, and a stormier pattern looks to resume across the Northern Plains.

First Preliminary Winter Outlook

This is my first winter outlook for the area, and other regions close to us. Most of the year's featured, a near neutral ENSO (discounting 2008, which had a weak La Nina), a negative PDO (discounting 1993-1994), and had teleconnection patterns that matched with this years.. I could not find a single year that even came close to matching with this year's teleconnections. In the past fifty years, there hasn't been a single instance where the NAO and AO fluctuated as much as it has. This is telling me that something is up with the observed wind patterns over the North Atlantic. For the teleconnections, the closest fits were 2008-2009, 1993-1994, and 1977-1978. As for precipitation patterns, the best fits were 2006-2007, 2008-2009, and 1977-1978.. I don't want to sound like I'm "wishcasting" (that's what happened last year), so I'll give you my first thoughts. These years were also checked for correlations in the AO and NAO, and there were only two years that corresponded, and those were 1993-1994 and 1977-1978. Some of you who are older, probably remember the winters of 93'-94' and 77'-78'. During the winter of '77-'78, the area saw temperatures about 10 degrees Fahrenheit below the normal average temperature. In the winter of 1993-1994, we saw temperatures about 4-6 degrees below average, mainly in the month of January. This may have biased my winter forecast, so don't expect it to be as cold as those years.

I'll start with storminess and precipitation. In actuality, this could go either way this year. In my personal opinion though, I believe that El Nino will be non-existent by the time December comes around. If this occurs, then I expect precipitation to be above normal in the Ohio Valley, all the way into the Eastern United States. Any place south of Indiana or west of Indiana will likely see below normal precipitation. The jet stream will likely be directed across the southern and central United States this year. The biggest storms will occur when the NAO dips to negative values, and the PNA also goes negative, forcing a large trough into the Midwest. For right now, I'm going to go out on a limb, and state that snowfall may be slightly above normal for the winter season.

I don't believe we will see another split flow jet stream, which will allow for a stronger jet stream, more dynamic storm systems, and colder weather for areas north of the jet stream. From Southern California into the Southeast, I expect above normal precipitation for the first part of the winter season, but near normal precipitation for the rest of the winter. In the east, coastal storms will be frequent so precipitation should be well above average. As for temperatures, the analogue years are nearly "black and white", meaning that some of the analogue years clearly show above normal temperatures across the Ohio Valley, Northeast, Upper Midwest, and other parts of the Northern United States, while the other half of the analogues show below normal temperatures across the Northern United States. When they were averaged, most of the United States should end up cooler than normal east of the Rockies. West of the Rockies, due to the strength of the western ridge, I expect above normal temperatures. In other words, there is a very good chance that we end up with below normal temperatures for the winter, but I will keep the original forecast at equal chances for above or below normal temperatures.

Rainy forecast for Today and Tonight

Some of the more important features on the weather map today will be the slowing cold front over the Ohio and Central Mississippi Valleys, the large and deepening upper level trough over and just to the north of the area, and a shortwave which will cause a wave to form along the frontal boundary. Currently, a very strong jet streak (145 knot wind speeds in the core over south central Canada to be precise) is rounding the western section of the trough. This will aid in the development of a open wave low pressure system later during the early afternoon and evening.

As the frontal system develops, increased cloud cover will overspread the region, especially during the afternoon hours. It may be sunny right now, but according to satellite imagery, thick, heavy cloud cover will move into the region during the next several hours. As the system develops, and lifting increases as the warm front strengthens, numerous rain showers will develop. Initially, it will take quite a while for the rain bands to get going due to the dry state of the atmosphere.. But once the storm system can draw in some moisture, rain will begin. For right now, I'm expecting the heaviest period of rain to be around 03z tonight or 11 p.m. as illustrated by the map below. The map below shows vertical motion. Where vertical motion is stronger, that's where the heavier rain will be at.

Rain showers will continue until the early morning hours, with only a few scattered showers left. By Saturday, yet another shortwave will approach the area, bringing an additional chance for showers.

This map is an isentropic map. A gradient in the red lines indicates a frontal boundary.

As for temperatures, today, I expect highs in the upper 60's to lower 70's, with lows in the lower 50's tonight. Rainfall amounts won't be that high, with about a quarter to a half an inch expected, at a maximum. For Saturday, temperatures will drop into the lower 60's, due to a cold front passage. Lows Saturday night will dip into the lower 40's. As for Sunday, highs will make it to about 57, after a secondary cold frontal passage. For the rest of next week, temperatures will begin to moderate, but some models are indicating another blast of cooler air to affect the region around Wednesday.

Additional Features and Thoughts on the Winter Outlook

This will be yet another quite technical article on behalf of my discussion about what will happen during this winter season. While it is quite uncertain about what will happen.. There are several factors that can be used to determine a winter's temperature and precipitation relative to average.

WARNING: SKIP THIS PART IF YOU DO NOT WANT THE TECHNICAL DETAILS

In this article, I will specifically be discussing atmospheric blocking and the observed jet stream wind patterns. One of the defining factors of last winter's weather was the observed lack of high latitude atmospheric blocking across Greenland and the Arctic. This was caused by the fact that a Sudden Stratospheric Warming event never occurred until the latter part of the winter, by which time it was well too late for any significant change in the winter pattern. The first variable I will be discussing is the North Atlantic Oscillation.. I won't go into detail about this variable, as I have explained quite thoroughly in other blog posts from last winter. Last year, its tendency was mainly positive. When the NAO is positive, below normal upper level heights (or below normal upper level pressure) exist over Greenland, and above normal upper level heights exist over the Central Atlantic, usually near the Azores extending eastward to Bermuda. This causes a stronger than normal height gradient (and thus a higher pressure gradient), which causes a stronger jet stream. In this type of pattern, the weather across the U.S. is normally variable (though some meteorologists falsely claim that a positive NAO is associated with warmer weather across the United States, which is not always the case...), but favors a warmer, and stormier weather pattern across the Central Plains and Midwest. When it is negative, below normal heights occur over the Central North Atlantic Ocean, while above normal heights occur over Greenland and Northeastern Canada. This causes a more meridonal jet stream pattern, and more stagnant weather pattern. The strong, looping jet stream will force cold air out of the Arctic and into the Eastern and Southern United States, as a negative NAO favors a trough over the U.S. Over most of the past several months, the NAO has trended negative.. While this gives no indication as to what it will be during the winter months, its trends during the fall can be rather significant to the winter forecast. During the late summer and early Fall of 2011, the NAO had been trending slightly negative, but abruptly went into the positive territory... Many meteorologists were going on the boat that the index would fall again by November and December. THIS DID NOT HAPPEN. The reason was because of the Arctic sea ice extent across the Arctic Ocean. Arctic sea ice extent became the highest in the last 12 years in October of last year, right after it had hit record lows. When Arctic sea ice extent is higher, heat transfer to the atmosphere is rather minimal, and easily favors the development of upper level troughs and thus the reason for the "Polar lows". When Arctic sea ice extent is below normal, heat transfer into the atmosphere is above normal, and favors the development of upper level ridges.. And when this happens, the NAO plummets, as well as another variable, known as the Arctic Oscillation, which is a very similar index.  Just last week, it was recorded that Arctic Sea ice extent was at its lowest on record. Now, whether that will mean colder weather during the winter, no one knows.

This is a map of Sea surface temperatures relative to normal as measured by satellites and buoys.  According to the NCDC, the far North Atlantic and Arctic Ocean SST anomalies have increased since last year. This is another indication that atmospheric blocking may set up during the upcoming winter.

Other variables that are looked at include the PDO, PNA, and many others. In this post, I would like to focus on the PNA.. Basically, when the PNA is positive, A ridge is usually evident in the Western U.S... There is normally a stronger Aleutian low, and below normal heights across the Southeast United States. When it is negative, trough is located in the western United States, a ridge in the Gulf of Alaska and normally a southwest jet stream pattern over a good chunk of the United States (good for storminess in the Ohio Valley). A positive PNA favors very cold weather and a stagnant weather pattern across the East (unless of course conditions are ripe for coastal storms). A negative PNA favors stormy weather, especially in the West, Midwest and Central Plains. This could go either way, but, according to ESRL/PSD data, the PDO (Pacific Decadal Oscillation) tends to correlate well with the PNA... Normally, when the PDO is negative, the PNA also averages neutral to negative. Of course, since the PNA varies on weekly timescales and the PDO varies on yearly time scales, it's very hard to tell any kind of pattern.

This is a chart of how the PNA index has varied over the past fifty years. So far, no pattern has been recorded by this particular index, unlike other atmospheric variables.

This is a chart showing both the variations of PDO and the PNA in comparison to each other. There is somewhat of a correlation between them, the actual calculated value of correlation is 0.250 for the past 10 years, which is quite a bit better than most variables correlations.

STOP!

In conclusion, I believe that all of this will influence the winter's weather patterns. In fact, I have come to believe that the PNA will average near neutral for the winter, which would favor a jet stream pattern through the lower Ohio Valley (depending on the development of the El Nino of course). Now, this is not my official forecast. This is only one of the many possibilities. I believe that with the recent development of record breaking low ice extent, a tendency for the NAO to trend negative over the past few months, the PDO index dropping, and SST anomalies, that the winter will feature near to slightly above normal precipitation in the Ohio Valley, in fact, mainly areas east of the Mississippi. For right now, with so much uncertainty, temperatures will be a "wild card"... Even though I believe that we have a better chance of seeing below normal temperatures across the area, historical data suggests otherwise. Only a few analogues that match up with the current year actually show below normal temperatures during the winter months. The ironic thing is that each of those respective winters featured particularly brutal cold outbreaks, mainly the winter of 1993-1994. My first official forecast will be released over the weekend, so expect it then. I will reveal my preliminary thoughts on storminess, temperatures, precipitation, and other things.

Another look at the Possibilities...

As I have stated in the previous post, my findings and conclusions were this yesterday: One; That the best matches for the year's forecast were the years of 2006, 1993, 1981, 1976, 1969, and 1966... There are a few other years, and I'm changing them.. Even those these years are the closest in the weather patterns, they are actually quite far from what we are experiencing.. This is the first year that I have made a winter forecast (this is my third year) where the year in question did not have even a close match... So, this one may go on intuition. One of things I would like to emphasize in this update is the ENSO pattern (tomorrow's update will feature atmospheric blocking and SSW's).. Across the Equatorial Pacific, the current El Nino is dying.. According to Climate Prediction Center charts, the above normal SST anomalies have been fading away over the past several months, and shifted westward, as the thermocline in the equator region moves upward (the dividing line of colder waters located about 200 meters below the surface of the ocean.)... This is associated with an increase in upwelling and thus a closer La Nina pattern. I would not be surprised to see a neutral pattern come in for the winter period, or even a weak La Nina. On average, most neutral ENSO winters feature above normal snowfall across the region, but colder than normal temperatures. But that all depends on other factors such as atmospheric blocking across the North Atlantic (which I will explain in tomorrow's post). Another factor that is contributing to the weakening of the El Nino is the fact that atmospheric wind and precipitation patterns are not responding. First of all, the trade winds have not really backed off (while they are weaker than last winter's trade winds, but that was brought on because of the original intensification of the short-lived El Nino back in July), and this is the reason for the westward advancement of the above normal sea surface temperatures.. For an El Nino to strengthen it needs to stay in the eastern ENSO zones. Other factors, such as a very strong negative PDO regime is likely affecting the development of the El Nino.

What this means is that this winter will likely not reflect El Nino weather patterns, which on average would usually mean above normal temperatures across this region, but with drier than normal weather. I expect with a farther north southern jet stream, that precipitation will likely be above normal. Right now, temperatures look to be the wild card. I will have this resolved by the time I have next week's article published. Until then, here are my current thoughts. If the ENSO event does turn into a weak La Nina or even stay neutral, I expect temperatures to be slightly below normal across the region. If the ENSO strengthens into a stronger El Nino, then I would expect near or slightly above normal temperatures for the region.

Some thoughts....

Some additional thoughts on this winter's outlook... Last winter as most of us recall, featured rather warm temperatures. This was in part due to the lack of cold air in Canada (it was also a rather warm year in western and Central Canada), and the fact that there was virtually no atmospheric blocking across the North Atlantic. Towards the latter half of the winter season, an SSW occurred over the Arctic regions. An SSW stands for Sudden Stratospheric Warming event. In theory, an SSW should lead to increased atmospheric blocking over the North Atlantic or the Arctic, approximately 2-4 weeks after the SSW has occurred. Last winter, it came too late, as very little extremely cold air had built up over western and central Canada. When conditions were favorable over Alaska for the build-up of a record breaking cold air mass, the jet stream patterns became unfavorable for the movement of this arctic air mass into the Eastern United States. This year, over the course of the spring and summer months, strong atmospheric blocking has set up across the North Atlantic. In fact, we just recorded the lowest NAO value on record back in June (Climate Prediction Center).. Right now, positive stratospheric temperature anomalies have been building across the North Pacific and Arctic regions, possibly in correlation with the strengthening negative PDO regime. This has lead to a drastic drop in NAO values over the past week or so, and the reason for the cooler weather. IF this pattern can stay in place for the next couple of months, it could possibly become the main winter weather pattern. This kind of a pattern would be very favorable for extremely cold winter weather, but drier conditions across the Northern U.S. Another signal I'm looking at is the ENSO conditions. If the CFSv2 long range forecast is correct (the first set of ensemble members), then the El Nino will weaken considerably by December, and become neutral. This remains consistent with the fact that El Nino's usually struggle to develop in the negative episode of the PDO. Of course I am still investigating this winter, and I will provide more updates as the week goes on, but at this point, there are three possible weather patterns that this winter COULD feature: One, a rather warm, and possibly wet winter associated with the El Nino (similar to 2006-2007). Two, a rather cold and dry winter, similar to the winter of 93-94. And three, a winter similar to 2010-2011 where the negative PDO, intense atmospheric blocking, and positive PNA patterns dominated and caused a rather cold and snowy winter. The most likely winter weather pattern at this point is number one, mainly based on historical analogues. After reviewing the data, this year is very unique in the fact that virtually no years in the historical record from 1951 onward even come close to having similar weather conditions to this summer and fall. This may be a rather unique winter season, and quite a bit different from the last winter season. I will discuss this in a related post tomorrow.

All in all, the most likely scenario for the winter is one that features near or slightly above normal temperatures, and likely above normal precipitation (given a strong southern jet stream, which will average farther north than normal).. 

Winter Outlook Release Date

I will have to review more data for the upcoming winter.. But I should be finished by next weekend. I will also publish the forecast in the paper.

As for what my preliminary thoughts are.. Based on the past winters, I expect that December could end up rather warm or just slightly above normal temperature wise, with near or slightly above normal precipitation (given an active southern jet stream that could be slightly farther north than on average.).. By January, the NAO (North Atlantic Oscillation), could drastically change after taking a brief dip into positive territory, and taking a sharp dip into the negative index values. I'm basing this off of the fact that in recent years, the NAO has been drastically changing and to near opposite ends of the spectrum over a time period of a few months... Take for instance this past summer and spring, we had one of the lowest values of the NAO on record. I believe this to be in part influenced by one of the lowest solar activity periods in the records. What could happen is that it will likely drop again this winter, leading to a much colder end to the winter season. By February, temperatures will likely remain cold...

This is only preliminary, and if El Nino decides to strengthen rapidly, all of these ideas will be null and void. I expect several updates on the winter forecast this fall.

First "Sneak Peek" Into the Winter Outlook

This is a map that I have compiled of my analogue years for the winter... The winter's used are 2006-2007, 1993-1994, 1969-1970, 1966-1967...

This would indicate a colder than normal winter for the region, but with precipitation near normal with snowfall above normal... I'm not sure if this is going to pan out, but this is the best I can do based on history.