26 January 2011 storm

 

This storm is known for the onset of the snow occurring 12 or more hours prior to when guidance suggested the onset, which had a very negative impact on morning rush hour over southern NY and into New York City.  Well over 1 foot of snow fell in southern NY and southern New England, including New York City and Long Island and most of it fell through the daylight hours into the evening.  While significant snows did fall over highly populated areas, the snow was not widespread enough to rank higher than a 1 on the NESIS Scale. 

 

Analyzing the forecast models/ensembles and data after the storm, revealed that deterministic forecast models showed respectable midlevel moisture and vertical motion as well as isentropic lift well in advance of measurable precipitation.  Even the ensemble probabilities for various QPF hinted at an earlier onset of the precipitation.  Still, the ability of precipitation moistening a dry surface based layer is always in question, and in this case, the precipitation, evaporation and moisture advection must have contributed to precipitation being observed earlier than the forecast models/ensembles suggested.

 

ECMWF

 

 

 

500 hPa forecasts

 

 

 

MSLP forecasts

 

 

 

QPF

 

GFS Ensemble

 

 

 

MSLP forecasts

 

 

Probabilities for a half in and 1 inch in 24 hours.

 

GFS

 

MSLP

 

 

850 hPa winds

 

NAM

 

 

MSLP

 

 

850 hPa winds.

 

Short Range Ensemble Forecast

 

 

 

MSLP

 

850 hPa winds

 

 

Probabilities for a half inch and inch of rain in 24 hours

 

 

Above:  Loop of 12Z 25, 00Z 26 and 12Z 26 January GFS RH and Omega in the 700-500 hPa layer with 6 hour QPF overlay.

 

 

Above:  Loop of 12Z 25, 00Z 26 and 12Z 26 January NAM RH and Omega in the 700-500 hPa layer with 6 hour QPF overlay.

 

 

Above:  Loop of 12Z 25, 00Z 26 and 12Z 26 January GFS Pressure and Isentropic Adiabatic Omega on the  300K surface.

 

 

Above:  Loop of 12Z 25, 00Z 26 and 12Z 26 January NAM Pressure and Isentropic Adiabatic Omega on the 300K surface.

 

  

 

Water vapor satellite imagery.

 

 

Visible satellite imagery.

 

 

Above:  Loop of radar imagery from 00Z to 06Z 26 January.

 

 

Preliminary category 1 on the NESIS Scale.