The 20020419 case involved fast-moving convection through ...



4-6 March 2001: “The Storm That Wasn’t”

The 4-6 March 2001 case study documents clearly show New Jersey as the area expected to receive up to two feet of snowfall, according to the NCEP model forecast discussion and the ETA model output, as of 3 March 2001. (Figs. 1 and 5)

A heavy snowstorm was expected with over 18 inches of snow throughout New Jersey according to existing NWS models. (Figs. 5 and 6) The actual snowfall totals ranged from measurable snow east of Philadelphia to 4.5 inches at New Brunswick to 6 inches at Newark Airport to 11 inches at Wantage. The NJWxNet was not operational for the 4-6 March 2001 event.

This case serves to highlight the potential of using a higher-resolution model specifically configured for the wide range of extreme weather that affects the New Jersey area. RAMS was initialized with the same dataset as the ETA model, thus it shared the same trend to overestimate the precipitation for the New Jersey area (Fig. 3). RAMS was configured at the time for local land-based storm systems, making it more difficult to accurately portray this ocean-based storm. However RAMS forecast significantly less precipitation and ended the precipitation period earlier than the ETA forecast. (Figs. 2, 3, and 5) RAMS also correctly located the rain/snow line about 40 miles south of New York City, whereas the ETA model maintained a snowfall event throughout the state. (Fig. 4)

The 4-6 March 2001 case presents evidence of the higher-resolution RAMS model providing a more accurate forecast than the ETA model for the location and severity of the event. NWS forecasters verified the ETA model inaccuracy by the conclusion of the event. (Fig. 7) RAMS may have recognized the “non-event” more accurately if initiated using NJWxNet data and configured more specifically for the NJ region to account for storms originating over the Atlantic Ocean.

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Figure 1: This model forecast discussion from the National Center for Environmental Prediction (NCEP) the afternoon of 2 Mar 2001 highlights the confidence of experienced meteorologists in the likelihood of a historic snowstorm for the Mid-Atlantic region:

EXTENDED FORECAST DISCUSSION FOR 05 THRU 09 MAR 2001

HYDROMETEOROLOGICAL PREDICTION CENTER...NCEP...NWS...WASHINGTON DC

3:38 PM EST FRI MAR 02 2001...FINAL VERSION.

POTENTIALLY SERIOUS E COAST STORM STARTING LATE ON DAY 3 (SUN).

THREAT OF HEAVY SNOW AND STRONG COASTAL WINDS CONTINUES FOR THE

MID-ATLANTIC..

...MODEL OVERVIEW AND DISCUSSION...

WE NOW HAVE HIGHER CERTAINTY THAT THERE WILL INDEED BE THE

DEVELOPMENT OF A MAJOR STORM ALONG THE EAST COAST...MAYBE EVEN A BLIZZARD...IN THE DAY 2-3 PERIOD.

...

THE LATENT HEAT RELEASE OF HEAVY PCPN...COUPLED WITH DE-

STABILIZATION AS VERY COLD TEMPS ALOFT REACH THE MID ATLANTIC

COAST...COULD GENERATE A VERY POWERFUL STORM SUN NIGHT INTO TUE FOR THE MID ATLANTIC AND SOUTHERN NEW ENGLAND AREAS. WE FEEL THAT THE AVN SCENARIO IS BASICALLY CORRECT. EAST COAST...WATCH OUT!

...

...EAST COAST STATES...

USING THE AVN AS OUR MAIN TOOL...WE LOOK FOR HEAVY SNOW SUN NIGHT

INTO MON OVER THE MID ATLANTIC AND SOUTHERN NEW ENGLAND COASTS.

THERE MAY BE BEACH EROSION AND COASTAL FLOODING...ALONG WITH WINDS EXCEEDING GALE FORCE ALONG THE IMMEDIATE COAST. FARTHER INLAND..MODERATE TO HEAVY SNOW AND BLOWING SNOW FROM VA THRU THE SOUTHERN HALF OF NEW ENGLAND. LOW WIND CHILLS WITH TEMPS GENERALLY IN THE HIGH TEENS TO MID 20'S. THERE COULD EVEN BE THUNDERSNOW. SNOW ACCUMULATIONS MAY EXCEED A FOOT FROM NORTHERN AND CENTRAL VIRGINIA NORTHEASTWARD THRU THE MAJOR METROPOLITAN AREAS. THE AVN HAS TARGETED NJ AS AN AREA WHERE AS MUCH AS TWO FEET COULD FALL.

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Figure 2: 48-hr ETA 12-hr total precipitation forecast for 7am on 5 March 2001

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Figure 3: 36-hr RAMS 12-hr total precipitation forecast for 7am on 5 March 2001, with maximum map values approaching 1 inch of liquid equivalent precipitation. Note the smaller extent of the precipitation versus the ETA map in the figure above.

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Figure 4: 36-hr RAMS 12-hr total forecast for 7am on 5 March 2001 for a) liquid precipitation and b) frozen precipitation with red approaching one inch of liquid equivalent precipitation. Note the accuracy of the rain/snow line.

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Figure 5: 56- and 60-hr ETA 6-hr total precipitation forecasts for 1pm and 7pm on 5 March 2001. Most of this “wraparound” precipitation was not observed, as highlighted in the NWS discussion in the last figure.

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Figure 6: a) 7pm 2 March 2001 RAMS event total precipitation and b) 7pm 3 March 2001 RAMS event total precipitation. Note the forecast time period for a) ends at 7pm 5 March 2001, and the majority of the precipitation in b) occurred between 7am 5 March and 7pm 6 March. Note the white color equates to roughly two inches of liquid equivalent precipitation. This figure highlights the early trend for RAMS to keep precipitation totals less than other models.

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Figure 7: 5 March 2001 discussion that summarized the inaccurate model output used for the NJ area.

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE MOUNT HOLLY NJ

900 PM EST MON MAR 5 2001

AVN BY FAR HAS BEEN THE MOST CONSISTENT MODEL WITH THIS EVENT. WE

OBVIOUSLY UNDERESTIMATED THE AMOUNT OF MELTING THAT OCCURRED ON THE FRONT END AND THE AMOUNT OF WARM AIR ALOFT THAT CHANGED THE SNOW TO SLEET. E.G 1 INCH OF SNOW/SLEET AROUND PHI HAD ABOUT .7 - .8 LIQUID EQUIVALENT DOWN HERE (AT MOUNT HOLLY). IF IT WAS JANUARY, 8-10 INCHES COULD HAVE FALLEN EASILY.

ON THE BACK END THE SURFACE LOW HAS INTENSIFIED AND DEVELOPED TOO FAR NE TO BRING THE HEAVIER PRECIPITATION INTO OUR REGION. AVN HAD MORE OF A HINT THAN THE ETA. ALSO THE DAYS ARE GONE IN WHICH THE MODELS ALWAYS UNDERFORECAST THE INTENSIFICATION OF LOWS...SOMETIMES THEY BOOM THEM TOO QUICKLY (12/30 COMES TO MIND) AND THIS CAN WREAK HAVOC WITH SNOW SITUATIONS. ALL IN THE ALL NOT A GOOD DAY TO BE A METEOROLOGIST IN PHL...THAT ROOT CANAL IS STARTING TO LOOK BETTER ALL THE TIME.

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