NE.Wx Snowfall Forecast Contest

Complete Results @ http://www.newx-forecasts.com/

Follow the left-panel link from '26^th Annual Snow Storm Contest > Verified Forecasts > ‘Storm #1’ to see the complete forecasters’ verification table by station.

In the table ...

Yellow cells indicate the best score in the category.

Forecast STP cells: yellow if within +/- 5% of observed STP.

Blue (Red) cells indicate the 1^st (4^th) quartile

SUMSQ: sum of square errors (measure of forecast accuracy accounting for magnitude and distribution of snowfall)

STP: storm total precipitation

TAE: total absolute error
AAE: average absolute error

Final Standings - all Forecasters

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Station by Station Comparison of Top 4 Forecasts and Observed Storm-total Snowfall (STP)

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Perfect Forecasts (Batting Average - Forecast Stations with No Error)

Best Station Forecasts (Batting Average - Forecast Stations with Lowest Absolute Error)

Best Station Forecast Busts (Batting Average - Forecast Stations with Highest Absolute Error)

Skill v. NWS ER WFOs

SKILL: positive (negative) skill value indicates a forecast/s improvement (degradation) over the NWS forecast.

BIAS: arithmetic difference between the average Forecast snowfall and the average Observed snowfall (averageForecast) – averageObserved).

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Consensus Forecasts … Extremes … and Observed Snowfall

Consensus forecast best @ ISP … JFK …ABE …DCA …RIC

NWS forecast best @ BGM … ISP … JFK … ABE … DCA

MAX forecast best @ BTV … SBY

MAX forecast less than observed @

MIN forecasts best @ ACY …IAD

MIN forecasts more than observed @

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Total Absolute Error and SUMSQ Error

Strong correlation (R = 0.909) between SUMSQ and TAE Z-scores

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Forecast by Observed Snowfall Scatterplots (Top 4 Forecasts)

A Forecast’s dashed BLUE trend line above (below) solid RED Observed snowfall line ==> over (under) forecast

R² value indicates how well the forecast captured the observed snowfall’s variability … i.e., R² = 0.874 ==> the forecast captured ~87% of the observed snowfall’s variability.

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Storm-total Snowfall Verification

Preliminary verification of storm-total snowfalls for SUN and MON based on reporting from CDUS41 (CLI) ... CXUS51 (CF6) ... METARs ... and PNS bulletins issued by NWS.

Good coverage and reporting.

Exceptions

SBY

- NWS Climatological Report (Daily - CLI) carried 'MM' for SAT snowfall-total and 0.53" liquid.

- NWS WFO Monthly/Daily Climate Data (CF6) carried 8.5" and 'M' for liquid.

- STP derived by an inverse distance weighting scheme with AKQ and PHI vicinity reports carried in their PNS bulletins for Sussex County ... DE and Worcester and Wicomico counties in MD came to 8.5".

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Snow-to-liquid ratios (SLR) less than 8:1 are not reported for stations with measurable snowfall b/c significant liquid and / or freezing precipitation also occurred during the verification period.

The 'TOT SLR' field is a quantity-weighted AVERAGE of those stations with at least an 8:1 SLR.

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Stations observing >= Trace: 17 (63%)
Stations observing > Trace: 6 (22%)

Given a station had measurable snowfall; stations observing at least:
4" - 5 (19%)
6" - 4 (15%)
8" - 1 (4%)

MAX snow melt-water (minimum SLR 8:1)
RIC - 1.18"
DCA - 0.81"
IAD - 0.73"

MAX precipitation (frozen + freezing + liquid)
RIC - 1.18"
DCA - 0.81"
IAD - 0.73"

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New daily snowfall record(s)
06-JAN-25
SBY: 8.5" (4.5"; 1970)
BWI: 6.6" (3.4"; 1989)
IAD: 6.0" (4.2; 2015)

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ORANGE cells: new daily record
GREY cells: data source(s) - PNS and / or METARs or inverse distance weighting
Trace amounts (displayed as 0.05") not included in STP

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