Using Tropical Cyclone Wind Speed Probabilities to Improve Public and Marine Text Forecasts
Operational Tropical Cyclone Wind Speed Probabilities
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Transcript of Operational Tropical Cyclone Wind Speed Probabilities
Operational Tropical CycloneWind Speed Probabilities
Richard Knabb
NOAA/NWS/National Hurricane Center
2007 Interdepartmental Hurricane Conference
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– 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
Overview of wind speed probabilities
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• What are the chances this wind event will happen to me at all?
• 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
What questions do these products answer?
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• 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
What questions do these products answer?
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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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Katrina Advisory #18
Magnitudes of Cumulative Probabilities Vary Greatly But Realistically
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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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Individual period probabilities help to understand timing uncertainty
Chances of tropical storm force winds in Miami
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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– 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
What is available via the NDFD(National Digital Forecast Database)?
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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
Graphics Widely Used in Emergency Management
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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.shtml