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.