The March 2001 East Coast Storm

	Storm overview
	Evolving model & forecaster perspectives
	Uncertainty & current forecast accuracy
	HPC’s role & communicating uncertainty
	Concluding remarks

Slide 2

Snowfall totals (NERFC)

The evolving model and
forecaster perspectives

		Day 7 (Mon, Feb 26)
			High model uncertainty
			Northwesterly flow in many model forecasts
			HPC – storm moving eastward out to sea
		Day 6 (Tue, Feb 27)
			Considerable uncertainty in the models
			Increased indication of east coast troughing
			HPC – potential for east coast storm with heavy snow possible
		Day 5 (Wed, Feb 28)
			Model uncertainty still high
			HPC – potential for east coast storm continues

The evolving model and
forecaster perspective (cont.)

		Day 4 (Thu, Mar 1)
			ECMWF ensembles not available
			Models starting to converge on development of major cyclone off mid-Atlantic coast (decreasing uncertainty)
			HPC – potential for very serious coastal storm for March 4 & 5, including heavy snow & beach erosion
		Day 3 (Fri, Mar 2)
			Some model runs differ from AVN/MRF on many details of east coast storm
			Despite decreasing uncertainty, significant uncertainty remained
			HPC – potential for a blizzard with 2 feet of snow
			Major pending west coast rain/snow storm
			NOAA press release

The evolving model and
forecaster perspective (cont.)

		Day 2 (Sat, Mar 3)
			Major increase in model forecast consistency
			Model development of the storm slowed
			HPC – high confidence for possible blizzard conditions in mid-Atlantic and the Northeast
			HPC – decreased likelihood of major snow event for DC to NY
			NOAA press conference
		Day 1 (Sun, Mar 4)
			Good model agreement
			Storm forms off the coast of North Carolina

Day 7
from
Monday,
Feb 26, 2001

Day 6
from
Tuesday,
Feb 27, 2001

Day 5
from,
Wednesday,
Feb 28, 2001

Day 4
from
Thursday,
Mar 1, 2001

Day 3
from
Friday,
Mar 2, 2001

Day 2
from
Saturday,
Mar 3, 2001

Day 1
from
Sunday,
Mar 4, 2001

Uncertainty & current forecast accuracy
(HPC QPF verification -- 1-inch threat score)

Slide 15

HPC’s Role &
Communicating Uncertainty

	Mission statement: to provide forecast, guidance, and analysis products and services 1) to support the daily public forecasting activities of the NWS and its customers, and 2) to provide tailored support to other government agencies in emergency and special situations.
	Vision statement: to be recognized by the NWS field offices and other forecast groups as a center of excellence for:
		heavy precipitation forecasting
		medium-range forecasting
		real-time numerical model diagnostics & interpretation
		surface analysis

HPC’s Role &
Communicating Uncertainty

		starting point
		second opinion
		focusing mechanism
		unifying influence
		emergency backup

HPC’s Extended Forecast Discussion
(released Mar 2, 2001, at 3:38 p.m.)

HPC’s Extended Forecast Discussion
(continued)

HPC’s Extended Forecast Discussion
(continued)

Concluding remarks

		Very busy forecast period with heavy rains in the SE preceding the Nor’easter, plus major rain event in southern CA.
			Events handled well overall, except for east coast megaopolis.
		Difficult forecast situation:  split flow / blocking
		Models indicated east coast storm a week ahead
		Given uncertainty in model guidance, very good consistency in HPC storm forecasts day-to-day
		Forecast uncertainty apparent in the model runs and mentioned in HPC narrative products
		Uncertainty not well perceived by the public
		Accuracy of precipitation forecasting has improved significantly, but still much room for improvement
		Public expectations increasing faster than forecast accuracy

Acknowledgements

		“Eastern Region Comprehensive Review of the   March 4-7, 2001, Northeast Snowstorm” by NWS   Eastern Region staff
		“March 4-6 East Coast Snowstorm” by Rich Grumm
		Doug Berz, HPC
		Ed Danaher, HPC
		Pete Manousos, HPC
		Brett McDonald, HPC
		Dave Reynolds, HPC