global warming

The December 5th Snow Event For Southern New Jersey
By Steven Dimartino

On December 5th, 2007 a clipper was diving through the Ohio Valley and redeveloping off the Mid Atlantic coast. As the new low rapidly developed, an area of moderate snow developed and moved from central Maryland through southern New Jersey. As a result, 4 to 6 inches of snow was recorded from Atlantic City to Cape May, New Jersey. What caused the snow band to develop andbecome so intense?

When looking at the development of a snow band, I work from the surface up to 500 mb. It is usually in these layers of the atmosphere were we find the answer to such developments. The intensification of the snow band can be considered both a meso and synoptic weather feature as small and large scale features worked in tandem forthis event.

From the surface to 950 mb, a strong temperature gradient was observed from the coast line to the coastal waters. This is a natural thermal gradient that was amplified by temperatures falling below freezing over much of the land mass. The result was strong convergence over much of the southern New Jersey coastal plain. This in turn produced strong low level forcing asthe precipitation approached.

Next, at 850 mb there were two important features developing as the new low pressure system developed off the Mid Atlantic coast. First, the thermal gradient at 850 mb was tightening up, which lead to strong upward motion of the air over the southern New Jersey coast. The gradient was tightening in response to the low level forcing, which in turn began to develop an upper low at this pressure field. Once again, additional support was given to the rising air and theprecipitation rates increased.

At 700 mb, the impact of the low level forcing began to focus the mid level forcing at this level. The air was cooling at this level as cold air advection was kicking in, thus the growth was rapidly improving and thus a colder snow crystal was developing. When snow crystals begin to shrink, the accumulation rate can increase should surface conditions support accumulation, whichit did.

Finally, at 500 mb, strong negative Potential Vorticity Advection (PVA) was approaching southern New Jersey. Vorticity Advection basically is another measure of rising air. In this case, very strong negative PVA was diving right towards the New Jersey coast. This additional PVA allowed the clouds to cool rapidly and for precipitation to reach optimal intensity. However, the PVA alone did not produce the moderate snow band. It was the focusing of the low level components that produced the strong snow band over southern New Jersey, which lead to the4 to 6 inch accumulations.

To summarize, the moderate snow event on December 5th was the result of several low, mid, and upper level features coming together at the right time. The negative PVA enhanced the upward motion along the coast that was already in the process of developing. This lead to the moderate snow fall and therefore the 4 to 6 inchesof snow.

Hello! My name is Steven DiMartino. I am the owner and meteorologist of http://NYNJPAweather.com - I have been a professional consulting meteorologist for 5 years, forecasting for some of the most important energy and transportation companies in the United States, specifically for the Northeast. If you are heading to the New York City or Philadelphia metropolitan areas, come to NYNJPAweather for the best weatherforecast in the region.

Article Source: http://EzineArticles.com/?expert=Steven_Dimartino
http://EzineArticles.com/?The-December-5th-Snow-Event-For-Southern-New-Jersey&id=874398