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.

Tomorrow's Thunderstorm Outlook

Weather Outlook for Tomorrow: I could not get a forecast for today out, but I can tell you that tomorrow will be very similar in terms of comfort and humidity... Currently, Fort Wayne International Airport (as of 3 p.m.) is recording a temperature of 86 with a dew point of 72, indicating a very humid and unstable air mass. This is supported by the fact that isolated showers and thunderstorms have developed to the southeast of Fort Wayne along a very weak and old frontal/convergent boundary (the boundary that was supporting an area of showers and thunderstorms earlier this morning across Michigan. Tomorrow's forecast will be very tricky, because it will depend on the timing a currently weak cold front over the Central Plains... A shortwave over southern Canada will ride southeast into the United States, intensifying the cold front and allowing it to slide eastward. As the cold front slides eastward, it will encounter a very humid and deep tropical air mass. The initial air mass ahead of the front will be quite dry, but several hundred miles ahead of the front, the air mass will still be moist and favorable for thunderstorm development.. Because of the initial dry air ahead of the front, I expect that thunderstorms will mainly be capable of producing damaging outflow wind gusts.. There is the possibility that these storms will organize into a linear line of storms by the time they begin affecting our area. I DO NOT believe that these storms will be widespread. In fact, they will be very isolated at first, and any line that does form will more than likely affect areas north of here in Southern Michigan.

For my official forecast, I expect high temperatures in the upper 80's to lower 90's tomorrow, with dew points in the lower 70's. Lows tonight and tomorrow will be in the upper 60's. For tomorrow night, I expect temperatures to drop into the middle 60's. As for the timing of any thunderstorm activity, though they will be widely scattered and isolated (at first, becoming organized by later in the evening, with areas mainly north of Route 6 having a better chance for storms to affect them), will be after 5 or 6...
Tomorrow, I should have an update on what I expect for the end of the week into next week.

Have a great afternoon!

Much Anticipated Pattern Change

After a rather warm and very humid end to the week, many of you are probably waiting for much cooler and drier weather.  I can tell you, that looks to be on the way by the end of the week. Right now, the remnants of the tropical system are slowly weakening just to the south of the area while sliding east at the same time. This is the reason for the extreme humidity and at times rain. On the upper air analysis this morning (Monday), a closed low was sitting over Canada, causing a weak trough to form across the Pacific Northwest. As upper level ridging builds across the far eastern Pacific near the West Coast, this will eventually push the closed low southeastward towards southern Canada and the eastern United States. As the trough moves this way, by Friday and Saturday, it will force a cold front through the area, with a low pressure center forming along the weakening front. At the time, it will be hard to resolve the details on what exactly will happen. The GFS ensembles are showing that a broad trough originating from the closed low will deepen by Saturday, allowing a rather strong high pressure region to cause a much colder air mass to become entrenched across the region. In fact, according to the GFS, temperatures could struggle to make it to the 70's by Sunday and Monday.. After that, warmer temperatures will return, but they will probably still struggle to reach into the 80's.
    What this indicates in the long-term is that the weak El Nino phase occurring in the equatorial Pacific is finally starting to have an effect on the world's weather. An El Nino phase usually favors troughing (which causes below normal surface temperatures) across the south and east. It also favors blocking across Canada, which is quite evident on the GFS ensemble forecast for the weekend. Already, this could be a precursor of what we see during the winter. I am not releasing a winter forecast yet, due to the uncertainty involved this year. In fact, this year's weather conditions are very similar to last fall. So, in fact, weather conditions during the winter could go either way. Most El Nino's across the area favor warmer than normal, and drier than normal conditions. Some El Nino's have been known to cause extensive troughing across the eastern and central United States during the winter, which suppressed the warm than normal conditions across the north and allowed for cold, arctic air to filter into the United States. This kind of pattern is evident when a certain long-term climate variable called the PDO is in its negative phase. While the PDO index has risen over the past few months, it is still negative, which should support a winter of colder than normal weather across most of the eastern United States. As for precipitation, that will be a bit trickier to forecast. It will all depend on whether the southern branch of the jet stream becomes dominant like it was last year. If so, most of our storm systems will come up from the southwest into the region, or they will swing in from the east as they are strengthening along the east coast. Right now, this is just speculation as to what is coming.
     As for the months of September and October, based on trends from what happened in August, I expect that September will likely see slightly above normal temperatures (our average high temperature in September is in the middle 70's.), especially every time the ridge breaks down in the west, which will send a heat surge into the Midwest. In October, if I base it on our last El Nino, then it will likely turn out to be cooler than normal, and wetter than normal. In fact, in October of 2009 (the last El Nino/negative PDO phase), the Midwest was hit by a snowstorm towards the end of the month! While I can see this happening, this October will probably not be characterized by such cold temperatures as it was then. This is because of the fact that El Nino is still struggling to develop across the U.S., and with a still large area of severe drought across the Central Plains, one or two day waves of extremely warm temperatures will still be possible. As for precipitation, with the jet stream dropping southward, and a better connection with Gulf moisture than we did last year, showers and thunderstorms will likely be just as frequent than last year. The only reason last fall was so wet, was because of the predominance of the southern jet stream, and the predominance of cut-off lows that continually formed. So I do NOT expect a wetter fall than last year, but it could still be fairly wet, especially in September.

Labor Day Forecast

For Today's Labor Day forecast: I expect temperatures to warm into the middle 80's under partly cloudy skies.. The remnant tropical low has weakened enough to allow only scattered cloud cover around its center. With a still moist air mass, and enough sunshine, weak to moderate instability will develop across the region. This will allow for the development of scattered showers and thunderstorms by later in the afternoon, especially in Northeast Indiana and Northwest Ohio... This shower and thunderstorm chance will exist through tomorrow. Other than that.. Have a great day!

IMPORTANT FORECAST UPDATE

IMPORTANT UPDATE FOR TOMORROW'S RAINFALL:

Well, here's what's going on: A shortwave over the Central Plains will move into the Western Great Lakes this evening and the overnight hours, bringing a chance for showers and thunderstorms. A str

ong and rapidly developing shortwave will drop south out of southern Canada, eventually phasing with the shortwave by tomorrow mid morning into the early afternoon. This will cause a jet streak to form, resulting in strong UVM (upward vertical motion) across the area, and the formation of rain bands. One of the reasons why I don't believe many thunderstorms will form is because of the fact that the warm, moist air mass gliding over the warm front will produce widespread clouds across the area by the morning hours. The front will intensify during the day, with the latest models suggesting the front will sit right over the area, which will make it very hard to forecast high temperatures. The low pressure system will develop along the front, turning it into an open wave cyclone. Showers and thunderstorms will form in response to the highly moist air mass moving into the region. In areas south of Route 6, there is the possibility that the atmosphere may destabilize by the afternoon, especially if the storm systems forms farther to the north. This could allow for an isolated severe storm, but at this time, it is not likely. Widespread showers and thunderstorms will likely continue into the late evening and possibly overnight hours before tapering off in the dry slot of the developing storm. A few showers and thunderstorms will persist across the area during the morning hours on Friday as the cold front slides through.

As for rainfall amounts, they will range from just over a half an inch mainly south of Fort Wayne, to possibly over two inches in isolated locations. This will be enough to help further ease drought conditions across the area.

As for temperatures, tomorrow's highs will range from the middle 70's to the lower 80's south of Route 6. Clouds will prevail for most of the day, with MAYBE a peak of sunshine in spots.

After a trough builds into the East in response to the storm system deepening the main trough, and allowing a seasonably cold air mass to reside across the area for the weekend, with highs in the lower 70's.

IMPORTANT SEVERE WEATHER UPDATE

 Even though a week ago it was said that this may be a significant severe weather event, it does not look to be that way now. There has been a change in this. Yesterday, it did not look like we would even get a severe weather event. But, it turns out the NCEP models were having problems handling the development of this system, and thus its dynamics. Here is what is likely to happen. Saturday morning, looks to start off clear and sunny across most of the area with some mid level and high level clouds likely across the area, from dying upstream convection. By this time tomorrow, the strong upper level wave that is currently located over South west Canada will likely be located over western Dakota. An ongoing MCS will likely be located over western Minnesota. During the day, as a surge of hot, dry air from the desert, rides up and over the warm, moist air at low levels, strong convective instability will set up. Dew p

oints are expected to rise into the low to mid 70's according to the 06z NAM. By late Saturday afternoon, a few isolated showers and thunderstorms will likely erupt as the cold front approaches the region. By early to mid evening (7 p.m. - 9 p.m.) the cold front will be close enough to the region to allow for the development of numerous thunderstorms to our west, which will likely organize into an MCS on the nose of a rapidly strengthening low level jet. This will likely be our only chance for severe weather if this happens. If the MCS does set up, it will not move very quickly given weak to moderate upper level winds. Though deep layer shear will be increasing, the most important factor will be low level shear. This could allow for damaging winds, especially if the low level winds align in the same direction. Strong upper level divergence from the developing jet streak over the Midwest will likely allow for the development of additional showers and thunderstorms during the overnight hours. Most thunderstorm activity should end by early Sunday morning, giving way to clearing skies and warming temperatures.

Have a great day!

Model Disagreement Continues

There is still considerable disagreement among computer models with the upcoming storm system and associated cold front.

This strong wave which is forecasted to track along the Canadian border will cause a jet streak to form over the Midwest. As I have said before, a jet streak is an area in the jet stream of higher wind speeds. The first thing that this causes is considerably higher vertical sh

ear. Since the jet streak will likely not be located over the area until after the cold front moves through, I would expect that this stronger vertical shear will only have an effect on storms that develop over Wisconsin and Iowa on Saturday afternoon. Second, since jet streaks are associated with winds that are not in geostrophic or gradient wind balance, they will have associated areas of diverging winds, which will destabilize the atmosphere over which the jet is located. An effect that it will have on our area is the fact that it could cause a strengthening of the low level jet, which transports heat and momentum into storms at low levels. If this jet is enhanced, severe storms will be more likely, given stronger low level shear, and continued destabilization of the atmosphere through the overnight hours.

Because of these factors, I have still determined that the main severe weather threat will be damaging winds, due to the fact that MCS development is likely ahead of the cold front in the form of a squall line, with embedded bow echoes.

This will be posted on the blog and I should have an update by afternoon.

Have a great day!

Storms threatening on the Horizon.

1. Morning Update:
   
   Good morning everyone! After a nice morning rain with a few rumbles of thunder (from a dying convective system in association with the upper level disturbance), I expect that the mid level cold pool responsible for the system will allow for moderate instability to develop this afternoon, as solar heating commences. With moisture pooling and convergence along the boundary, dew points will increase into the upper 60's and lower 70's mainly south of Route 6 this afternoon. CAPE values will rise in the range of 1500-2500 across a good portion of the area. This, in combination with the associated cold front and shortwave, will allow for the development of scattered strong thunderstorms this afternoon. The main threats will be heavy rain and gusty winds in the strongest storms. Upper level divergence in association with a developing upper level jet streak will also help prepare the atmosphere for thunderstorm development, and at the same time providing a source of bulk shear, for downdraft/updraft separation. This could allow for some localized severe weather in some areas.
   
   As for timing, I expect that most of the thunderstorm activity will develop around and after 3 this afternoon. It will likely organize into multicell clusters at first, organizing into possibly an MCS south of the area by the late evening hours.
   
   As for the long-range forecast, a weak shortwave could push a weak cold front into the region by Thursday and Friday, causing isolated showers and thunderstorms, but with a surface anticyclone residing from the last cold front, surface moisture will be lacking, limiting storm development. By Sunday, we have bigger issues. Models continue to forecast the movement of a strong shortwave and associated storm system along the Canadian border by Saturday and Sunday. Ahead of the system, a surge of warm air from the Desert Southwest will cause temperatures to jump into the lower and middle 90's on Saturday, and possibly Sunday. A surge of moisture from the Gulf of Mexico will also make the air sticky and humid. The moisture will cause the atmosphere to become unstable by Sunday, with CAPE values as high as 4000 J/kg. With higher shear values, severe weather looks to be a good possibility. The GFS continues to vary considerably with the amount of instability, with the 00z run forecasting 5000 J/kg of instability, while the 06z run is now forecasting 3000 J/kg or less of instability across the area. I will have to continue to monitor the situation, but to me it looks as if another significant severe weather outbreak may be possible.
   
   Have a great day!
   
   Joshua Steiner
   Senior meteorologist

   

Record-breaking Heat Continues

With upper level ridging continuing over the area, I expect that temperatures will continue to rise, especially as the low level flow veers to the southwest and west, which will continue to pump warm air into the region. Highs today will range from the middle to upper 90's under sunny skies. By tonight, as the ridge begins to flatten, warm dry air from the plains will advect into the region, causing temperatures to jump once again on Tuesday, with highs over 100 possible. All of this will continue with humidity levels up once again, which will allow heat indices to rise above 100. By Wednesday, a cold front will approach from the north, and cause a slight chance for showers and thunderstorms. By Thursday and Friday temperatures will drop back into the upper 80's.

Derecho Storm Facts.

Here are some of the facts that I have gathered about the horrific storms that ravaged the area last Friday afternoon.

Originally, the storms formed along a boundary that separated warm, moist air from warm, dry air to the north. The storms formed in far Western Illinois as the boundary lifted northward. An upper level disturbance initiated the violent thunderstorms, and caused them to move eastward into the Chicago area, producing winds of over 60 mph at the time.  In our area, temperatures were quickly warming into the middle 90's, with moist air moving into the region from the southwest, with dew points eventually approaching the low to middle 70's just before the storms hit the Fort Wayne area. Due to the highly unstable and potent air mass in existence across the area, the storms strengthened rapidly as they left Chicago. At the same time, the storms followed the boundary southeastward into the Fort Wayne. Minutes before the first gust of wind hit the Fort Wayne area, Doppler Radar recorded winds of almost 100 mph at an altitude of 2500 feet above the surface, right before that same patch of winds hit the Downtown area.  It was hard for anyone to prepare for the onslaught that was coming, as the line of storms, called a derecho (De-RAY-sho), were moving at a forward speed of nearly 80 mph! Most storms only move at speeds of 20 to 30 mph. As the storms moved through Fort Wayne, the line once again rapidly intensified in the still highly unstable environment. According to the Storm Prediction Center, a wind gust of 91 mph was recorded at Fort Wayne one of the highest wind speeds ever recorded in the area, while winds of 88 mph just to the northeast of Fort Wayne, producing incredible damage, with widespread tree and structural damage all throughout the city. As the storms strengthened, Doppler Radar also detected strong rotation as the storms passed over New Haven. The National Weather Service then issued a Tornado Warning for East Allen County, Paulding County, and Van Wert County. By the time the storms hit Antwerp, winds of almost 80 mph were reported, according to the Storm Prediction Center (National Weather Service), with even greater damage and widespread tree damage throughout the town. When the storms hit Paulding, a wind gust of 84 mph was recorded near PCH hospital. Even though the storms were extremely violent, they produced minimal rainfall amounts, with most areas seeing a quarter to a third of an inch of rain. Even the highest rainfall amounts were only in the range of 0.4 to 0.5 inches. These storms continued to strengthen as they moved southeast out of the area, knocking out power to almost 700,000 households in the state of Ohio. In fact, the derecho continued all the way to the Mid-Atlantic and out into the ocean, causing considerable damage and widespread communication failures in cities such as Washington D.C. Even though the storms cause more damage in the Eastern states then here, we still recorded the highest wind speeds of the entire event! According to the National Weather Service, this is likely one of the worst storms ever to hit the Northeast Indiana, Northwest Ohio region, and likely one of the worst derecho/squall line events in the Mid-Atlantic and Ohio Valley states ever recorded. At one point, the storms caused a total of more than 3 million power outages at the same time, more power outages than Hurricane Irene produced in the Mid-Atlantic states. From what I have heard on news sites and other places, 22 deaths were attributed to be a direct result of the storm, most of them were from people smashed by trees. This will go down as one of the worst derecho events to the United States, behind the series of derechoes that hit the Upper Midwest in 1995 and '96.

I will be writing an article about the formation of derechoes, and how we can prepare for them, in a couple of weeks.

Historic Heat Wave

     After many, many days of 90 degree temperatures in a row, many records were broken that have not been reached since the years of the Great Dust Bowl back in '34, and '36 (some of the hottest years on record at Fort Wayne). In fact, some all time record high temperatures have been breached several times throughout the heat wave.

     Before I describe all of the records that were broken, I want to give you some background information on why this heat wave formed, and what factors likely exaggerated the effects of an especially historic and legendary heat wave. As most of you probably remember, last winter was a very warm and wet (wet as in a lot of rain) winter. In fact, it came out to be one of our warmest on record, with every month of the winter season, December, January, and February recording temperature surpluses over 6 degrees above normal. While no record highs were set until the meteorological winter season had officially ended, we had quite a few days where temperatures were 20 degrees above normal, especially in February. Usually, during a normal winter season, the area receives a good winter freeze for several weeks, holding the moisture from the late Fall rains and early winter snows. During a warm winter though, evaporation rates are way up because the ground isn't frozen for long enough to hold moisture in. This is why coming into March, our top soils were already quite dry, regardless of the heavy winter rains. Usually, when the strengthening solar radiation hits the normally wet soils of our area, some of heat energy goes to evaporating soil moisture (which ultimately is a cooling process), while the rest goes to raising the temperature of the ground, which conducts into the lower atmosphere, causing a rise in surface temperature. When the ground is relatively dry, less heat energy goes to evaporating water, and more heat energy goes into heating the ground, which effectively raises the temperature of the lower atmosphere much higher and more quickly than a normally wet ground would. This also has an effect of reducing the relative humidity of the atmosphere, which ultimately hinders thunderstorm development. By the time the March “heat wave” hit the area, temperatures were much warmer than they otherwise would be, pushing daily temperatures above normal. Higher temperatures correspond to higher evaporation rates, which deprive the soil of its moisture. At the same time, the synoptic scale wind patterns, driven by the ocean currents and other large scale factors, favored ridging over the area, which means that high pressure is above the area. Higher pressure (pressure rises or more politically correct “height” rises) usually correspond to subsidence in the lower atmosphere (downward motion), and downward motion results in warming by compression, causing a rise in low and mid level temperatures and clear, sunny skies. This further hindered rainfall development during most of April and May. By May, we had two official heat waves (which normally does not occur), with temperatures in the first heat wave reaching the lower 90's, and temperatures during the second heat wave breaking all-time records for two days straight. This is when drought conditions developed across Northeast Indiana, while Northwest Ohio experienced abnormally dry (D0) conditions. With the same synoptic scale patterns that had started during the late winter, the high pressure area or upper level ridge continued to move back into the region after cooler periods of weather. Even in the cooler periods of weather, dryness continued intensifying the drought. By mid-June, a classic heat wave set up across the United States, with records broken in quite a few places. Here, temperatures were in the middle to upper 90's for 4 or 5 days in a row, until the heat broke on June 21 with a violent thunderstorm in some spots. At Fort Wayne International Airport, precipitation for that day was a mere 0.19 inches, while just north and west of Antwerp, Doppler Radar estimated that almost 2 inches of rain fell, right along the state line (my rain gauge recording 0.25 inches of rain from that storm in Antwerp). With continued dry conditions, the next heat wave set up in about a week's time, with the following week reaching well into the 100's, highs officially at Fort Wayne International Airport tied the all-time record high at 106, while Defiance Memorial Airport hit a record of 107 on the same day. During the next several days into July, upper level ridging built back into the area after the incredibly violent storm moved through. The heat wave culimnated by the middle of the week of the Fourth of July, with temperatures 101 and above for each and every day until Sunday. This was an unprecedented event, having four consecutive days above 100 degrees. This has never happened in the history of Fort Wayne with the next closest run of 100 degree temperatures occurring back in July of 1988, with only three consecutive days. With continued heat throughout the rest of the month, I expect that this July will become the hottest July on record, breaking last year's record. (This post will be updated as more information comes in.)

Most of the past heat waves of this year were rather dry with humidity levels not having much influence on the heat index. In the heat wave we had in the last week though, relatively wet soils from the violent thunderstorms and the maturing corn canopy contributed to excessive humidity, with dew points in the low to mid 70's occurring during the hottest part of the heat wave. This contributed to the heat indices that were over 110 at times. Also, favorable flow from the Gulf of Mexico, plus a series of upper level disturbances enhanced moist flow into the region. In theory, this should have produced multiple rounds of thunderstorms to help mitigate (which it did at times) the heat, but so far it has failed to do this because of a lack of strong lifting mechanisms, and strong capping (warm mid level temperatures) has thus far prevented widespread thunderstorm activity.

This heat wave's effects have also been exaggerated by the fact that the powerful derecho that slammed into the region, caused millions of power outages from Indiana to Washington, D.C. As of this writing (Friday, July 6, 2012), nearly 1.5 million are still without power in the areas affected by this storm in Ohio, West Virginia, and Virginia. Many people are without air conditioning during one of the worst heat waves in many years.

For what I think will happen in the long run, given no significant rainfall in the near future, drought conditions will continue, contributing to above normal temperatures, and exacerbating heat waves that plague the area. This will likely continue into August and even September before the changing climatic variables and ENSO phases within the Pacific affect the long-range patterns.

Extended Heat Wave Possible.

Even as the post-clean up process from Friday's storms is underway, another heat wave is on the horizon. Except this one will last an entire week. In fact, the National Weather Service has issued an Excessive Heat Warning for the area. The National Weather Service said that they are expecting a period of heat which will feature temperatures in the upper 90's to the lower 100's and heat indices well above that. This heat wave will be characterized by high humidity and maximum sunshine, which only make it worse for the many thousands of people who still need power. Even the heat does not exactly fit criteria for the excessive heat warning, it was issued because of its duration and impact. This heat wave is caused by a building heat dome or upper level ridge moving in from the west. This will allow for several days of quiet weather. By next weekend though, temperatures will reach their maximum on Saturday, near or over 100. Then a cold front will be forced through the area, cooling temperatures back into the lower 90's and upper 80's.