Transcript Operational Tropical Cyclone Wind Speed Probabilities Richard Knabb NOAA/NWS/National Hurricane Center

Operational Tropical Cyclone
Wind Speed Probabilities
Richard Knabb
NOAA/NWS/National Hurricane Center
2007 Interdepartmental Hurricane Conference
Overview of wind speed probabilities
– Replaced strike probabilities in 2006
– Describe chances of a weather event at any
specific location
– Convey chances of wind speeds of at least
particular thresholds
• 34 kt (tropical storm force)
• 50 kt
• 64 kt (hurricane force)
– Account for combined uncertainty in official track,
intensity, and size forecasts
– Extend to 5 days
– Include inland locations
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What questions do these products answer?
• What are the chances this wind event will happen
to me at all?
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Do I need to prepare?
Cumulative period probabilities
NHC and CPHC graphics and text products
Northern hemispheric grids sent via WMO headers
National Digital Forecast Database (NDFD) CONUS grids
• When is the event most likely to start at my
location?
• How much time do I have left to prepare?
• Individual period probabilities
• NHC and CPHC text products
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What questions do these products answer?
• What are the chances the event will be occurring at
my location during a specific period?
• (example) Will hurricane-force winds occur in my city on
Saturday night?
• Incremental probabilities
• NDFD
• Might go out via WMO headers by 2008
• Being incorporated into WFO products
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Probabilities Convey Uncertainties in
Track, Intensity, and Size Forecasts
Ernesto Advisory #11
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Magnitudes of Cumulative Probabilities
Vary Greatly But Realistically
Katrina Advisory #5
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Magnitudes of Cumulative Probabilities
Vary Greatly But Realistically
Katrina Advisory #18
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Changes to Graphics for 2007
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2006 Operational 120-h Graphic (64 kt)
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2007 Final 120-h Graphic (64 kt)
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2007 Preliminary 120-h Graphic (64 kt)
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Chances of
tropical storm
force winds in
Miami
Individual period probabilities help
to understand timing uncertainty
X
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Dealing With Small Probabilities
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A Challenge During Ernesto
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A Challenge During Ernesto
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A Challenge During Ernesto
Hurricane
Watch
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A Challenge During Ernesto
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What is available via the NDFD
(National Digital Forecast Database)?
– Cumulative and incremental probabilities
• Updated four times daily (00, 06, 12, 18 UTC)
• 6 hourly 0-120 h
• 34, 50, and 64 kt
– CONUS domain only
• 5 km grid spacing
– Experimental during 2006, declared operational for
2007 hurricane season
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NDFD CONUS Domain
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Probabilities from NDFD Website
www.weather.gov/forecasts/graphical/sectors/conusTropicalDay.php#tabs
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Probabilities in Hurrevac
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Graphics Widely Used in Emergency Management
Going forward
• Continue outreach and education
• Compare probabilities with
watches/warnings
• Account for varying forecast confidence?
• Enhance Hurrevac capabilities
• Experimental storm surge probabilities
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For Additional Information…
www.nhc.noaa.gov/aboutnhcprobs.shtml
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For Additional Information…
www.nhc.noaa.gov/archive/2005/index.shtml25
For Additional Information…
[email protected]
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