Historic end of February Storm Stage 1:  23-24 February (Click on images for larger display)

 

A complex 2 stage historical winter storm affected much of the northeastern U.S. during the last week of February 2010.  The first stage was a strong upper impulse that originated in the southern stream and tracked northeast from the southeastern U.S. to south and east of New England, within the eastern periphery of a developing stronger closed upper low.  The first storm was unconventional in that deep southerly flow brought warm advection and low level jet convergence and moisture advection/convergence, yet the predominant precipitation type across the region was snow.  In fact, many areas experienced a foot or more of snow, in some cases nearly 2 feet, especially in higher elevations.  This storm was being advertised in a range of terms from “Significant storm”, to “Big Storm”, to “February Fury”, to “Snowicane” by different sources of weather information.  This caused a debate within the meteorological profession on how to communicate significant hazards to the user community.  Some commentary can be found here.

 

All guidance sources were consistent multiple days in advance with respect to timing and track of the surface and upper features, and overall snowfall and liquid equivalent precipitation.  However, only within 2 days of the onset did the guidance truly distinguish the 2 separate events that composed the entire period of storminess.

 

 

 

Above:  Loops of the 00Z 23 February and 12Z 23 February GFSEnsemble MSLP mean and spread.  Note the consistency, and at the end of the loops, the developing primary surface low off the Carolinas, which became the predominant stage 2 storm.

 

 

Above:  Four panel of 850 hPa temperatures from the 00Z 23 February GFS, NAM, ECMWF and GGEM, valid 12Z 24 February.  Note the temperatures supported snow, even with the deep southerly flow that was present but not shown.

 

 

 

Above:  Four panel of liquid equivalent QPF from the 00Z 23 February and 12Z 23 February GFS, NAM, ECMWF and GGEM.  Note the high amounts from eastern and southern NY into western New England.

 

 

 

Above:  Raw snowfall forecasts from the 00Z 23 February and 12Z 23 February GFS.  Note the widespread 12”+ over eastern and southern NY and western New England.

 

 

 

Above:  Raw snowfall forecasts from the 00Z 23 February and 12Z 23 February NAM.  Note the widespread 12”+ over eastern and southern NY and western New England.

 

 

 

Above:  Loop of water vapor satellite imagery.  Note the unusual southerly flow, but note particularly the upper low diving south into the northern plains and Great Lakes, that eventually becomes the primary upper low over and off the eastern U.S.

 

 

Above:  Visible satellite picture showing the unusual cloud structure off the eastern U.S. as the deeper cloud cover is dominated by southerly flow.

 

 

 

 

Above:  Radar loop from KENX (left) during the heaviest snowfall, and northeastern sector (right) for most of the duration of the stage 1 storm.  Note the southerly flow indicted in the movement of the radar returns.

 

Any comments, questions or suggestions, please mail to:Neil.Stuart@noaa.gov