Doug Simonian

A Brief Overview of the Weather for the Next Few Days

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After the storm we had on Tuesday moved out of the area, we saw sunny skies and chilly weather on Wednesday as cold air filtered into the area behind the storm system. Today and Friday will have quite similar conditions, as a zonal flow across the county will not allow for any major dips in the jet stream to support strong storms.

A strong high pressure system has moved into the eastern half of the country, just to our south. This will provide our area with sunny skies and westerly winds for today, with temperatures in the mid 40s for most of the area. Tonight/Friday morning’s low temperature should be in the upper 20s in most of the region, with low 30s in more urban locales.

The 00z GFS forecast at 500mb, valid for Friday at 2pm. The pattern across the country is zonal, leading to no major storm systems for our area.

For Friday’s forecast, I’m going to show a couple of visuals. At 500mb, you can see the zonal flow across most of the country, which is helping to keep things quiet, for the most part. There is a ridge of warmth in the Central Plains which is heading eastward, which will warm us up a tad for Saturday and especially for Sunday and the days after that. Also, you can see a very weak area of vorticity in Michigan associated with a small shortwave trough that is heading eastward. This, combined with the fact that the warm air to the south and west will be overrunning the chillier airmass to the north and east will help to provide clouds and showers to the region for Saturday. The rain, if any, though, should be quite light and not cause too many problems.

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Doug Simonian

A Technical Discussion on Tuesday’s Snow

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We have another November snowfall event on the way for tomorrow – which is pretty unprecedented. It should not be a major snow event, but at the very least it should whiten the colder surfaces in most locations.

Forecast models have been showing a pretty weak disturbance traversing across the country from west to east, projected to pass south of Long Island. There won’t be much in the way of wind with this system because the storm itself will not be strong enough to create much of a pressure gradient with the high pressure to the north. However, despite the weak storm, precipitation should spread throughout the New York Metro region via overrunning – warm air to the south is colliding with cold air to the north, creating lift and precipitation.

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John Homenuk

Another autumn snowfall possible Tuesday

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NAM Model showing simulated radar precipitation types at 2pm on Tuesday November 27th, 2012. Notice the rain/snow line over Central NJ and along coastal areas of New Jersey, Long Island, and Connecticut.

Storm Overview

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Many areas having already received a pre-winter snowfall in Early November, a second wintry system is on the way Tuesday — one which could provide another light to moderate snowfall before the start of meteorological winter on December 1st. November snowfalls are not unheard of, but are rare — and seeing two in one month is exceedingly rare. This storm doesn’t look to pack the same significant potential as the first one, as it will be a much weaker system with less heavy banding. The heavy, slow moving bands of snow are what were largely responsible for the high snowfall amounts in the early November event, known in meteorology as deformation bands. These bands form where storms produce enhanced areas of lift and can often produce snowfall rates of 1-3″ per hour. Our system is swinging through from the west-northwest, and will eventually move off the coast and start strengthening once it’s well to our northeast.

Even despite the system being suppressed a bit, without any explosive strengthening or development, there will be a some moderate precipitation. The question becomes whether or not this precipitation can fall and stick as snow. This will be much easier inland, and in the higher elevations. Near the city and on the coast, there will be warmer air in place at the surface. This means that in order to cool the air, heavy precipitation needs to fall. Forecast models indicate that precipitation could fluctuate between rain and snow in these areas, depending on how heavy the precipitation is falling. This does not bode well for accumulating snow in these areas.

Snow and rain could begin as early as 8am Tuesday, and will continue throughout the day. The heaviest precipitation is expected to fall between 12 and 4pm, with precipitation lightening afterwards..but possibly continuing through the evening rush hour. By later Tuesday evening, the storm is expected to head to our north and east and precipitation will wrap up over Long Island and Connecticut.

Keep reading for details and forecast graphics/snow forecast maps…

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Tom Stavola

Winter Outlook 2012-13

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Introduction/Methodology:

Last winter featured a highly dominant pattern of lower pressures in the Arctic and higher pressures in the mid-latitudes, especially the United States. This was a classic +AO/NAO regime in which the strong jet stream precluded the amplification of cold troughs into any part of the US. As a result, the November-April period of 2011-12 was one of the warmest and least snowy on record for the lower 48 States. This winter, since the outlook is being issued a month later than last year, I hope to avoid unforeseen patterns with November’s data helping to strengthen statistical and physical correlation for the December-January-February (DJF) meteorological winter season. Factors that will be considered, but not limited to: ENSO, PDO, PNA, NAO, AO, EPO, Solar activity / trends, Stratospheric activity / trends, QBO, forecast modeling, pattern persistence and analogs (years with patterns similar to the present, rolled forward into the future to aid in long term projections). Keep in mind that we are still in the “pioneering” phase with some aspects of long range forecasting, and thus, one cannot attribute the same expectations as one would for a short or medium range forecast (1 month or less). Furthermore, do not expect the level of detail that is provided in short or medium forecasts to appear in long range outlooks. The hope is that the data we collect from the autumn season will aid in forming a general picture of the temperature and precipitation patterns of the future. These data take the form of numerous statistical correlations concerning teleconnection indices, as well as perceived physical forcing mechanisms in both the atmosphere and stratosphere.

Pacific Signaling

The El Nino Southern Oscillation (ENSO) index should be in a predominately warm-neutral phase for this winter season, meaning, region 3.4 sea surface temperature anomalies (SSTA) in the central tropical pacific will be in the 0.0c to +0.5c range.

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