Modeling Tropical Modeling Tropical Cyclone Gridded Wind Cyclone Gridded Wind Field Forecasts Field Forecasts 26th Conference on Hurricanes and Tropical 26th Conference on Hurricanes and Tropical Meteorology Meteorology 3—7 May 2004 3—7 May 2004 Miami, FL Miami, FL Ken Waters Ken Waters Joel Cline Joel Cline National Weather Service National Weather Service Honolulu, Hawaii Honolulu, Hawaii
16
Embed
Modeling Tropical Cyclone Gridded Wind Field Forecasts 26th Conference on Hurricanes and Tropical Meteorology 3—7 May 2004 Miami, FL Ken Waters Joel Cline.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Modeling Tropical Cyclone Modeling Tropical Cyclone Gridded Wind Field Gridded Wind Field
Forecasts Forecasts
26th Conference on Hurricanes and Tropical 26th Conference on Hurricanes and Tropical MeteorologyMeteorology
3—7 May 20043—7 May 2004Miami, FLMiami, FL
Ken WatersKen Waters
Joel ClineJoel Cline
National Weather ServiceNational Weather Service
Honolulu, HawaiiHonolulu, Hawaii
Modeling Tropical Cyclone Gridded Modeling Tropical Cyclone Gridded Wind Field ForecastsWind Field Forecasts
• BackgroundBackground
• Process/AlgorithmProcess/Algorithm
• IssuesIssues
• ResultsResults
• Future PlansFuture Plans
Background: PurposeBackground: Purpose• The goal:The goal:
– An hourly forecast estimate of surface wind speeds and An hourly forecast estimate of surface wind speeds and direction for 31 island points in the West Pacificdirection for 31 island points in the West Pacific
• Needed for:Needed for:
– Terminal Aviation Forecasts (TAFs) for 24-hour periodTerminal Aviation Forecasts (TAFs) for 24-hour period– Hourly wind forecast needed to help determine start/stop Hourly wind forecast needed to help determine start/stop
times for Tropical Storm and Typhoon Watches and times for Tropical Storm and Typhoon Watches and WarningsWarnings
– Wind grid information for possible initialization of digital Wind grid information for possible initialization of digital wind grids (National Digital Forecast Database) wind grids (National Digital Forecast Database)
• Official Tropical Cyclone Warnings Official Tropical Cyclone Warnings are produced by the DoD Joint are produced by the DoD Joint Typhoon Warning Center in Pearl Typhoon Warning Center in Pearl HarborHarbor
• Forecast of position and maximum Forecast of position and maximum sustained wind speed for Hours 00, sustained wind speed for Hours 00, 12, 24, 36, 48, 72, 96, and 12012, 24, 36, 48, 72, 96, and 120
• Estimated wind radii by quadrant for Estimated wind radii by quadrant for Hours 00-72Hours 00-72
• For winds inside the Radius of For winds inside the Radius of Maximum Wind (RMW), use:Maximum Wind (RMW), use:
influence of radius maximum r
WindMaximum of Radius R
storm ofcenter from distance radial r
0
0
000
0
rRrwhere
R
rRVrV
Process/Algorithm:Process/Algorithm:
• Interpolate storm forecast to obtain hourly Interpolate storm forecast to obtain hourly positions and maximum wind speedpositions and maximum wind speed
• Apply the wind formula for a regular grid Apply the wind formula for a regular grid centered upon the storm at each hourly centered upon the storm at each hourly position as well as for selected point position as well as for selected point locations (e.g., islands) at each hour based locations (e.g., islands) at each hour based on distance from storm to the islandon distance from storm to the island
• Compute simple wind direction orthogonal Compute simple wind direction orthogonal to line between the storm and the pointto line between the storm and the point
Process/Algorithm:Process/Algorithm:
• National Digital Forecast Database requires National Digital Forecast Database requires offices to produce surface wind grids of at offices to produce surface wind grids of at least 5 km resolution every 3 hoursleast 5 km resolution every 3 hours
• Following example shows a method of Following example shows a method of populating the wind field based solely on the populating the wind field based solely on the wind radii (quadrant) information inside the wind radii (quadrant) information inside the warning --- not using Rankine vortexwarning --- not using Rankine vortex
Issues:Issues:• Determination of Radius of Maximum Wind (RMW) Determination of Radius of Maximum Wind (RMW)
--- not part of forecast but input to the formula--- not part of forecast but input to the formula
• Determination of the exponential “shape” factor Determination of the exponential “shape” factor • How rapidly does wind speed fall off as one moves away from How rapidly does wind speed fall off as one moves away from
center?center?
• Variances include spectrum from huge storm down to “midget” Variances include spectrum from huge storm down to “midget” typhoonstyphoons
• Inherent dangers with using a highly deterministic Inherent dangers with using a highly deterministic approach to describe difficult-to-predict tropical approach to describe difficult-to-predict tropical cyclone movement and intensitycyclone movement and intensity
• Create netCDF grids for possible use in Create netCDF grids for possible use in initializing National Digital Forecast initializing National Digital Forecast Database wind gridsDatabase wind grids
• Explore methods to estimate exponential Explore methods to estimate exponential factor and Radius of Maximum Windfactor and Radius of Maximum Wind
Questions?Questions?
• Text data files can be found at:Text data files can be found at:– http://www.prh.noaa.gov/hq/regsci/windhttp://www.prh.noaa.gov/hq/regsci/wind– Graphics planned for this spring/summerGraphics planned for this spring/summer
Ken WatersRegional Scientist
National Weather Service, Pacific Region737 Bishop St., Ste. 2200