ATM 401/501Status of Forecasting: Spring 2013

1. Forecasting at NCEP• Environmental Modeling Center

http://www.emc.ncep.noaa.gov/• Ocean Prediction Center

http://www.opc.ncep.noaa.gov/• National Hurricane Center

http://www.nhc.noaa.gov/• Hydrometeorological Prediction Center

http://www.hpc.ncep.noaa.gov/

Link to HPC verification page

• Storm Prediction Center http://www.spc.noaa.gov/

MotivationMotivationFlooding is a leading cause of weather-related deaths

"Improvements in QPF and

mesoscale rainfall prediction need to

be a top NWS research and training

priority." 2009 SE US Flood Service Assessment

Atlanta: Sept. 21, 2009

Nashville: May 1, 2010Cedar Rapids: June 2008

Cedar Rapids: June 2008

Bias: The basic formula for computing the bias is

Forecast / Observed

This quantity gauges the accuracy of areal/station coverage of a specified precipitation threshold amount, regardless of accuracy in location. An ideal forecast would have Forecast = Observed to yield a Bias of 1.

Threat Score (TS): The formula for computing the TS is

Correct / (Forecast + Observed - Correct)

For a perfect forecast, Correct = Forecast = Observed to yield a TS of 1. The worst possible forecast, with Correct = 0, yields a TS of zero.

Threat and Bias Scores

Extreme Events are ChallengingExtreme Events are Challenging

Forecast

improvement of

extreme events

(4”) lags

improvement of

more common

events (1”)

Tennessee ExampleTennessee Example12 UTC 1 May – 12 UTC 3 May

Observed HPC Deterministic

(Issued 12 UTC 1 May)

12 UTC 1 May – 12 UTC 3 May

Observed 95th percentile

Tennessee ExampleTennessee Example