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Climate: An Ocean Effect Snowstorm on Long Island - January 19, 2005

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Ocean Effect snowstorm on Long Island, January 19, 2005A recent NorthShoreWx article described a Long Island Sound effect snowfall on the north shore. Such snowfalls are relatively rare, but not unheard of. On Wednesday January 19, 2005 a highly unusual Ocean Effect Snowfall developed on a south wind and left between 3 and 6 inches of snow across most of Suffolk County.

Arctic air had been in place over the region for days and caused heavy lake effect snow in western New York State. One thin single band lake streamer off of Lake Ontario even persisted long enough to cause a brief heavy snow shower over parts of New York City and Nassau County late in the evening of January 17. The remnants of the great lakes streamers then rejuvenated over the ocean and caused significant snows over the waters south of Long Island, which is very common during the winter months.

On January 19, an approaching Alberta Clipper quickly turned the winds starting just above the surface to a long south-southwesterly fetch over the relatively warm ocean water (7C) while temperatures above the surface remained very cold. The temperature difference (Delta-T) between the sea surface and the atmosphere about a mile up (850mb) remained near 18C throughout the day.

The resulting instability combined with extra lift from the approaching clipper caused multiple bands of ocean effect snow to develop during the morning. These bands continued reforming and streaming north over Suffolk County for much of the day. By late afternoon, some light system snows from the clipper arrived over Long Island, although it is likely that local enhancement continued to occur until later in the evening when veering winds shut off the ocean effect. Click the radar image above right for a seven hour radar loop of this event. The file is approximately 1.5 megabytes, so be patient if you are on a dial-up line.

The following are some representative snowfall totals across Suffolk County as reported in a Public Information Statement issued by the National Weather Service in Upton:

   MANORVILLE             5.2  1100 PM  1/19
   UPTON                  5.2  1000 PM  1/19
   BAITING HOLLOW         4.8   830 PM  1/19
   EAST ISLIP             4.8   715 PM  1/19
   HAMPTON BAYS           4.5  1025 PM  1/19
   RIVERHEAD              4.5   730 PM  1/19
   MOUNT SINAI            4.5   645 PM  1/19
   CUTCHOGUE              4.0   700 PM  1/19
   STONY BROOK            4.0   700 PM  1/19
   SAG HARBOR             4.0   900 PM  1/19
   MILLER PLACE           3.8   740 PM  1/19
   SETAUKET               3.3   700 PM  1/19
   CENTEREACH             3.0   930 PM  1/19
   SAINT JAMES            3.0   830 PM  1/19

The following Skew-T charts are from the Upton, NY atmospheric soundings collected that day (7AM and 7PM local time). Click either of the images to see a larger chart.

Skew-T chart, OKX 0012Z, January 19, 2005.  Click to enlarge Skew-T chart, OKX 0000Z, January 20, 2005.  Click to enlarge