1 / 17

Long Term Trends in National Hurricane Center Watches and Warnings

This presentation examines the data and verification methods used to evaluate the long-term trends in hurricane watches and warnings issued by the National Hurricane Center (NHC). The study finds that the average length of NHC hurricane warnings has decreased in the 2000s, reversing a 35-year trend of increases. The average lead times of warnings and watches are now 34 hours and 50 hours, respectively. The warned location has a 1 in 4 chance of experiencing hurricane winds, while the watch location has a 1 in 5 chance.

jimnaylor
Download Presentation

Long Term Trends in National Hurricane Center Watches and Warnings

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Long Term Trends in National Hurricane Center Watches and Warnings Mark DeMaria, NOAA/NESDIS/StAR, Fort Collins, CO and James L. Franklin, NOAA/NCEP/TPC, Miami, FL Presented at the Interdepartmental Hurricane Conference March 8, 2007

  2. Outline • Introduction • Data and Verification Methods • 1963-2006 sample • Verification and Long Term Trends • Conclusions

  3. Hurricane Watches and Warnings • Watch – hurricane conditions are possible within 36 hours • Warning – hurricane conditions are expected within 24 hours • Watches and Warnings (WWs) re-evaluated every 6 hours • Can be updated at any time in special advisories • End points of WWs selected from coastal “breakpoints”

  4. Input to Watches and Warnings • Major considerations • Forecast track, intensity, wind structure • Forecast uncertainty • Larger area included than receives hurricane winds • Other factors • Time of day • 5 PM warnings preferred over 11 PM • Storm surge and evacuation lead times • Input from coordination call

  5. Data and VerificationMethods • All WW breakpoints for contiguous U.S. digitized for 1965-2006 • Cindy 1963 and Cleo 1964 also included • 183 coastal breakpoints used to define coastline • Supplemented with 157 intermediate points • Brownsville, Texas to Eastport, Maine = 3600 nmi • “Observed” hurricane winds from NHC data • NHC best track position, intensity • Operational 64 kt wind radii • Best track radii since 2004

  6. Breakpoint 2 Breakpoint 1 “Observed” Hurricane Wind Region

  7. WW Length and Lead Time • WW Length • Size of WW for an individual advisory • Total length with WW at any time in storm lifetime • WW Lead Time • Time between first issuance of WW and arrival of hurricane winds • Valid only for points that received hurricane winds

  8. Lengths of Hurricane Warnings from Individual Advisories1963-2006 N=890

  9. Top Five Warning Lengths • Gloria 1985 Sep 27 1053 nmi • Floyd 1999 Sep 16 1045 nmi • Bob 1991 Aug 18 984 nmi • Charley 2004 Aug 13 906 nmi • Belle 1976 Aug 10 838 nmi

  10. Hurricane Warning Length Decadal Averages

  11. Storm-Average Warning Lead Time(time from when warning was first issued at a location to arrival of hurricane winds)

  12. Hurricane Warning Lead Time Decadal Averages

  13. Hurricane Watch Length and Lead TimeDecadal Averages Length Lead Time

  14. Warning and Watch Statistics(2000-2006) • Average individual warning length 290 nmi • Average storm-total warning length 362 nmi • Average storm-total length w\ hurricane winds 89 nmi • Prob. of warned point receiving hurricane winds 25% • Lead time of hurricane warning 34 hr • Average individual watch length 210 nmi • Average storm-total watch length 425 nmi • Average storm-total length w\ hurricane winds 85 nmi • Prob. of watch point receiving hurricane winds 20% • Lead time of hurricane watch 50 hr

  15. Conclusions • The average length of NHC hurricane warnings has decreased in the 2000’s reversing a 35 year trend of increases • Average warning length is 290 nmi • The average lead times of warnings and watches are now 34 hr and 50 hr • Long-term averages are 27 hr and 40 hr • Warned location has 1 in 4 chance of hurricane winds • Watch location has 1 in 5 chance of hurricane winds

More Related