Thursday, March 02, 2006

Postmortem on March 2, 2006 Winter Storm

by Tom Thunstrom

  • My call for the event.

  • Forecast Challenge Calls for the event.


  • Snowfall, Philadelphia International Airport: 0"

  • First Observation of Precip, 7 AM




  • ********************STORM TOTAL SNOWFALL********************

    LOCATION STORM TOTAL TIME/DATE COMMENTS
    SNOWFALL OF
    (INCHES) MEASUREMENT


    NEW JERSEY

    ...MORRIS COUNTY...
    MARCELLA 2.2 530 PM 3/2 SPOTTER

    ...SUSSEX COUNTY...
    WANTAGE 4.1 530 PM 3/2 SPOTTER
    NEWTON 2.8 405 PM 3/2 PUBLIC
    LAKE HOPATCONG 1.5 445 PM 3/2 PUBLIC
    GREEN TOWNSHIP 1.5 1015 AM 3/2 SPOTTER

    ...WARREN COUNTY...
    STEWARTSVILLE 1.8 930 AM 3/2 SPOTTER

    PENNSYLVANIA

    ...MONROE COUNTY...
    POCONO SUMMIT 2.0 235 PM 3/2 SPOTTER

    ***********************STORM TOTAL ICE***********************

    LOCATION STORM TOTAL TIME/DATE COMMENTS
    ICE OF
    (INCHES) MEASUREMENT


    NEW JERSEY

    ...ATLANTIC COUNTY...
    HAMMONTON 0.01 1200 PM 3/2 SPOTTER

    ...MIDDLESEX COUNTY...
    EDISON 0.20 420 PM 3/2 SPOTTER

    ...MORRIS COUNTY...
    CHATHAM 0.25 420 PM 3/2 SPOTTER

    ...SUSSEX COUNTY...
    NEWTON 0.15 405 PM 3/2 PUBLIC

    PENNSYLVANIA

    ...BUCKS COUNTY...
    PERKASIE 0.10 333 PM 3/2 SPOTTER

    ...LEHIGH COUNTY...
    MACUNGIE 0.10 908 AM 3/2 SPOTTER

    ...MONTGOMERY COUNTY...
    POTTSTOWN 0.10 400 PM 3/2 PUBLIC
    ROYERSFORD 0.05 330 PM 3/2 PUBLIC

    ...NORTHAMPTON COUNTY...
    WILLIAMS TOWNSHIP 0.20 245 PM 3/2 SPOTTER

    Source: NWS Philadelphia


    This was a difficult event to forecast and to be honest, I was surprised in how it played out, especially for the Lehigh Valley and Northern and Western suburbs where I thought there would be a period of snow at the onset. This storm was more disorganized and brought less precipitation to the table than it was forecast to.

    Part of that had to do with a tongue of dry air which separated the moisture stream to the south of the storm from the actual disturbance. Notice the dark shades poking down into PA and MD on the map above. This lack of phasing between the moisture pool and the disturbance led to a weaker system. Also, the low tracked north of forecast guidance. This slight northward adjustment (about 40-50 miles) made all the difference from a snowfall in the Lehigh Valley and an icy, sloppy mess.

    Grading my forecast of the storm

    Timing:
    Call was 4-7 AM, started in the 6 AM hour at Philadelphia. A for timing.

    Accumulations:
    Call for Philadelphia was 0-2". 0" fell at the airport. A for accumulations at PHL.
    Call for Allentown was 4-6". 0" fell at Allentown. F for accumulations at ABE.
    Call for Trenton was 2-4". 0" fell at Trenton. F for accumulations at TTN.
    Call for Poconos was 4-6". 2" fell at Pocono Summit. C for accumulations.

    (Each inch or hour outside of range is one grade level down with 0 accumulations when accumulations are predicted getting automatic F's.)

    Using the 4.0 scale (4 for A, 3 B, 2 C, 1 D, 0 F). 10 points total/5 grades = 2.0 or a C for the area, with an A for Philadelphia. Not a great forecast on my part and I should have been LESS confident in my thinking for the Lehigh Valley than I was. As the case has generally been most of this winter, I handled the immediate Philadelphia area pretty well. This time around I busted in the Lehigh Valley (sorry guys!).


    As for the media, Channel 6 was the only casualty as their forecast for 1-2" came up high for Philadelphia. Everyone else did well in their forecast for Philadelphia, but busted badly to the north as well.