4595 petersen - american public works association petersen [email protected] 301-763-8201 nasc...
TRANSCRIPT
4/28/09
2009 NASC 1
NAsc 2009
Hydrometeorlogical Prediction Center (HPC) Forecast Operations Branch
Winter Weather Desk
Dan Petersen
301-763-8201
NAsc 2009
Goals of Presentation
• Review HPC
winter weather desk forecasts
• Review winter weather desk performance for recent events
• Discuss use of snow to liquid ratio forecasts
NAsc 2009
Weather Forecast Office Watches/Warningshttp://www.nws.noaa.gov/
4/28/09
2009 NASC 2
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Weather Forecast Office Snow accumulations
http://www.weather.gov/forecasts/graphical/sectors/conus.php?element=PoP12
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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 http://www.hpc.ncep.noaa.gov/wwd/winter_wx.shtml
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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
4/28/09
2009 NASC 3
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HPC Products and ServicesWinter Weather Desk
Probabilistic Snow Forecasts are issued for 4, 8 and 12
inches, and icing for 0.25 inches
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HPC Winter Weather Desk Day 3 probabilistic snow forecast verification
2006-8
24
25
26
27
28
29
30
4"
8"
12"
HPC forecaster improvement
over Brier skill score for all
NCEP model and ensemble members
(2007-2008 top, 2006-2007 bottom)
2007-8
2006-7
0
5
10
15
4"
8"
12"
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73
74
75
76
77
78
Day 1
Day 2
Day 3
2007-8
36
38
40
42
44
46
48
Day 1
Day 2
Day 3
HPC Winter Weather Desk Days 1-3 probabilistic 0.25” ice forecast
verification 2006-8
HPC forecaster improvement
over Brier skill score for all
NCEP model and ensemble members
(2007-2008 top, 2006-2007 bottom)
2006-7
4/28/09
2009 NASC 4
NAsc 2009
The displayed model and ensemble low positions show the
uncertainty of the low positions- the black line represents the
HPC preferred track
HPC Products and Services-Winter
Weather Desk Low Tracks Graphic
NAsc 2009
Review of Recent Heavy Snow and Icing Events
• January 26-28 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
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January 26-28, 2009 ice storm northern
AR to southern MO and KY
4/28/09
2009 NASC 5
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Paducah KY Jan 28 2009
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
NAsc 2009
Radar Images 4 pm CDT Jan 26, 4 am CDT Jan 27, 4 pm Jan 27, 4 am Jan 28 2009
NAsc 2009
Analysis of freezing rain amounts
Jan26-28 2009
Areas of
1.5 to 2
inches of
ice from
southwest
KY to
northern
AR
4/28/09
2009 NASC 6
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HPC Day Three Forecast Probability of
0.25 inches of freezing rain
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HPC Day Two Forecast Probability of
0.25 inches of freezing rain
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HPC Day One Forecast Probability of
0.25 inches of freezing rain
4/28/09
2009 NASC 7
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Fargo flooding eases as blizzard pounds region
Source: USA Today Mar 31, 2009
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24 hour Snowfall Analysis 7 am CDT Mar 31 2009
Large area of
8-12 inches
eastern and
southwest SD
and southeast
ND
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HPC Day One Forecast Probability of 4 inches (left), 8 inches (center), 12
inches (right)
4/28/09
2009 NASC 8
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24 hour Snowfall Analysis 7 am CDT Mar 24 2009
18-30 inches
in the Black
Hills of SD
Large area
of 8-12
inches
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HPC Day One Forecast Probability of 4
inches (left), 8 inches (center), 12 inches (right)
NAsc 2009
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
4/28/09
2009 NASC 9
NAsc 2009
Climatology of Snow to Liquid Ratios (courtesy Marty Baxter)-
http://www.eas.slu.edu/CIPS/slr.html
highest
average
over the
northern
Rockies
greatest
variability
near the
Great
Lakes
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Section 6b: The UWM Neural Network Snow Ratio Forecast Tool
Web GUI interface at
http://sanders.math.uwm.edu/cgi-bin-snowratio/sr_map_main.pl
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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
4/28/09
2009 NASC 10
NAsc 2009
Section 6b: Verification for Jan 22-23 2005 heavy snow event
Section 6b: Verification for Jan 22-23 2005 heavy snow event
0
5
10
15
20
25
30
SLR Climo UWM
Detroit, MI
Albany, NY
Gray, ME
January 22-23 2005-average snowfall amounts of a
foot in Detroit, Albany, and Gray, ME
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.
Roebber et al, Weather and Forecasting June 2007, pp. 676–684
NAsc 2009
Day three forecast from model ensemble liquid equivalent precipitation and snow to
liquid Ratio
Forecast of
18-20 inches
of snow in
the Black
Hills of SD 72
hours in
advance of
the event
NAsc 2009
Snow and Ice reports• Current real-time reports from Weather Forecast Offices:
• http://www.nws.noaa.gov/view/validProds.php?prod=LSR
• http://www.nws.noaa.gov/view/validProds.php?prod=PNS
• Archived reports from National Climatic Data Center, Cocorahs, and National Operational Hydrologic Remote Sensing Center:
• http://lwf.ncdc.noaa.gov/oa/climate/research/snow
• Cocorahs maps of observed snowfall: http://www.cocorahs.org/Maps/ViewMap.aspx?type=snow
• http://www.nohrsc.noaa.gov/nsa/reports.html?region=National&var=snowfall&dy=2009&dm=3&dd=10&units=e&sort=value&filter=0
