The Non-Storm of January 13th, 2008
On the days leading up to January 13th, 2008; model guidance was showing the potential for a major snow storm to hit the New York City metropolitan area with accumulations of over 6 inches of snow. However, by night of January 13th, 2008; the actual precipitation was rain and plenty of busted forecasts. What happened to the snow? Did meteorologist miss something? Could something have been overlooked? I’ll examine exactly what happened and give my thoughts on the overall forecast.
My Forecast Thoughts: Before finding out what went wrong, let’s go back and look at my thoughts leading up to this event.
Confidence on my forecast for this storm was low from the start. The air mass was marginally cold enough for snow and under normal circumstances would lead to a cold rain rather than any snow. This was the general idea for the forecast on January 8th through the 10th. A basic rain/snow mix with little if any accumulation.
However, on the night of January 10th, model guidance started to send signals that the storm could be more. The short wave over the Tennessee Valley was hinting at being stronger while dynamics at 700 and 850 mb were showing signs of supporting significant cooling of the atmosphere. This cooling would occur due to air rising quickly over much of New Jersey, southeastern New York, and Connecticut. The low pressure would rapidly develop at all levels as precipitation starts banding. When I say banding, this means that areas of precipitation becomes very heavy due to the rapidly rising air. Sure, the surface air was marginal, but 850 temperatures will crashing to -3 degrees Celsius and should this lifting occur, the surface temperatures would cool enough to snow. The snow would be a heavy wet snow at that! Further, model guidance also showed the potential for convective snowfall or thunder snow. Thunder snow has the potential to produce snowfall rates of 1 to 3 inches per hour.
So up until Sunday afternoon, all aspects to support a heavy, wet snowfall were being advertised. Jet dynamics supported divergence and difluence over the northern Mid Atlantic. The shortwave was being forecasted to be in the perfect position. This would lead to rapid development of the mid level features. Most importantly the 850 mb low would develop and deepen just off the New Jersey coast, which means colder air would be pulled towards the coast at the height of the storm. Strong omega values, which is a sign of rapidly rising air, was seen continuously at 700 mb. Meanwhile, a strong coastal front was showing signs of enhancing the low level lifting needed to complete the cycle. Rising air from the surface to 250 mb, which would be more than enough to cool the boundary layer and thus produce a heavy snowfall.
WHAT WENT WRONG: Well, we all know this morning, that the New York City metropolitan area did not get a heavy snowfall. Some areas did not get any snow at all, but just a driving rain storm with a few snow flakes mixed in. So what went wrong?
After carefully studying 00Z observations and the water vapor loops, what happened to this storm is clear now. Up to the point of the forecast, model guidance showed every aspect of forcing needed for a heavy snow storm to come into phase at exactly the right time. In other words, the supposed development was perfect from 950 mb up to 250 mb. Then reality hit.
The short wave that was to enhance the development of this storm from the surface to the mid levels picked up some forward motion on the late afternoon of January the 13th. This was due to the diving upper level low moving towards the Great Lakes. As a result, this forced the development of the entire system to begin much earlier. Precipitation was racing towards New Jersey by sunset, which was roughly 4 hours earlier than expected. The faster disturbance also retarded the development of the mid levels. With the surface low pressure being forced to move faster, the time for the 850 mb low to develop was gone. Therefore, instead of colder 850 mb air being pulled towards the coast, the thermal gradient remain stagnant. This means that the lack of a developing 850 mb low significantly weakened any potential for upward motion to develop over the coastal plain. With out the strong upward motion of air, the temperatures at the surface remained too warm. Sure, the coastal front developed nicely which lead to very impressive rain totals over central New Jersey, however with out the aid of rising air throughout the entire column of the atmosphere, the cooling needed for this storm was not present. Therefore rain was the result.
Conclusion: This storm shows exactly why forecasting a winter storm for the Mid Atlantic and Northeast is very difficult. In this case, everything needed to be perfect and was advertised to be just that. However, due to a slightly increase in speed of the vorticity maximum at 500 mb by roughly 3 to 4 hours, the lifting needed for this storm feel apart, and so did many forecasts with it.
Hello! My name is Steven DiMartino. I am the owner and meteorologist of http://www.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 weather forecast in the region.
