Goals of Presentation

Transcription

1 Hydrometeorlogical Prediction Center (HPC) Forecast Operations Branch Winter Weather Desk Dan Petersen Review HPC winter weather desk forecasts Review winter weather desk performance for recent events Discuss use of snow to liquid ratio forecasts Goals of Presentation Weather Forecast Office Watches/Warnings NASC 1

2 Weather Forecast Office Snow accumulations HPC Winter Weather Desk Issues heavy snow and icing forecasts and collaborates these forecasts with local Weather Forecast offices September 15- May 15 Internal 24-hour Snow and Ice accumulation probability graphics for days one through three. Public and technical versions of low tracks graphic depicting synoptic scale surface low tracks associated with heavy snow or ice. Heavy Snow and Ice Discussion Forecasts and discussions posted at HPC Winter Weather Forecast Process New model guidance arrives HPC uses model/ensemble blender on left to generate draft graphics sent to NWS WFOs only 2009 NASC 2

3 HPC Products and Services Winter Weather Desk Probabilistic Snow Forecasts are issued for 4, 8 and 12 inches, and icing for 0.25 inches HPC Winter Weather Desk Day 3 probabilistic snow forecast verification HPC forecaster improvement over Brier skill score for all NCEP model and ensemble members ( top, bottom) " 8" 12" " 8" 12" 0 HPC Winter Weather Desk Days 1-3 probabilistic 0.25 ice forecast verification HPC forecaster improvement over Brier skill score for all NCEP model and ensemble members ( top, bottom) Day 1 Day 2 Day Day 1 Day 2 Day NASC 3

4 HPC Products and Services-Winter Weather Desk Low Tracks Graphic The displayed model and ensemble low positions show the uncertainty of the low positions- the black line represents the HPC preferred track Review of Recent Heavy Snow and Icing Events January ice storm northern AR to southern MO and KY March 24 heavy snow in Wyoming/western Dakotas March 31 heavy snow in the Dakotas/Minnesota January 26-28, 2009 ice storm northern AR to southern MO and KY 2009 NASC 4

5 Paducah KY Jan The storm has been blamed in at least 42 deaths, including nine in Arkansas, six each in Texas and Missouri, three in Virginia, two each in Oklahoma, Indiana and West Virginia and one in Ohio. Most were blamed on hypothermia, traffic accidents and carbon monoxide poisoning. Source: The Associated Press Radar Images 4 pm CDT Jan 26, 4 am CDT Jan 27, 4 pm Jan 27, 4 am Jan Analysis of freezing rain amounts Jan Areas of 1.5 to 2 inches of ice from southwest KY to northern AR 2009 NASC 5

6 HPC Day Three Forecast Probability of 0.25 inches of freezing rain HPC Day Two Forecast Probability of 0.25 inches of freezing rain HPC Day One Forecast Probability of 0.25 inches of freezing rain 2009 NASC 6

7 Fargo flooding eases as blizzard pounds region Source: USA Today Mar 31, hour Snowfall Analysis 7 am CDT Mar Large area of 8-12 inches eastern and southwest SD and southeast ND HPC Day One Forecast Probability of 4 inches (left), 8 inches (center), 12 inches (right) 2009 NASC 7

8 24 hour Snowfall Analysis 7 am CDT Mar Large area of 8-12 inches inches in the Black Hills of SD HPC Day One Forecast Probability of 4 inches (left), 8 inches (center), 12 inches (right) Review of Snow Density Is the snow going to be heavy and wet or light and powdery? Buffalo NY Oct 13, 2006 Almost a million residents of the Niagara Frontier lost power 2009 NASC 8

9 Climatology of Snow to Liquid Ratios (courtesy Marty Baxter)- highest average over the northern Rockies greatest variability near the Great Lakes Section 6b: The UWM Neural Network Snow Ratio Forecast Tool Web GUI interface at Section 6b: The UWM Neural Network Snow Ratio Forecast Tool The neural network runs ten different forecasts. Probability distributions are determined from these forecasts. For a heavy, wet snow, look for high probability of the heavy category and low probability of the light category 2009 NASC 9

10 Section 6b: Verification for Jan heavy snow event January average snowfall amounts of a foot in Detroit, Albany, and Gray, ME SLR Climo UWM The observed snow to liquid ratios were more than twice the climatology values, with the neural net providing a 50 percent improvement over climatology in a case where the snow ratio values were more than twice their normal. Detroit, MI Albany, NY Gray, ME Roebber et al, Weather and Forecasting June 2007, pp Day three forecast from model ensemble liquid equivalent precipitation and snow to liquid Ratio Forecast of inches of snow in the Black Hills of SD 72 hours in advance of the event Snow and Ice reports Current real-time reports from Weather Forecast Offices: Archived reports from National Climatic Data Center, Cocorahs, and National Operational Hydrologic Remote Sensing Center: Cocorahs maps of observed snowfall: &dm=3&dd=10&units=e&sort=value&filter= NASC 10

11 Questions or comments? Dan Petersen NASC 11