OPERATIONAL CONSIDERATIONS FOR HURRICANE MODEL DIAGNOSTICS / VERIFICATION

Transcription

1 OPERATIONAL CONSIDERATIONS FOR HURRICANE MODEL DIAGNOSTICS / VERIFICATION Richard J. Pasch National Hurricane Center Hurricane Diagnostics and Verification Workshop Miami, Florida 4 May 2009 NOAA/NESDIS

2 AccuWeather s Joe Bastardi on Hurricane Diagnostics: I don t understand why some storms are getting named and others are not getting named. from an article in The Wall Street Journal entitled For Early Hurricane Forecasts, Consult a Telepath, 4/29/09 NOAA/NESDIS

3 OUTLINE WHAT WE FORECAST NOW; WHAT WE MAY FORECAST IN THE FUTURE VERIFICATION, CURRENT & FUTURE SOME RECENT OPERATIONAL FORECAST CASES/ISSUES REQUIREMENTS: WHAT WE NEED FOR DIAGNOSTICS

4 WHAT WE FORECAST NOW Track: center positions at 0, 12, 24, 36, 48, 72, 96, and 120 hours Intensity: max sustained winds (and gusts) at 0, 12, 24, 36, 48, 72, 96, and 120 hours Size/Structure: radii (by quadrant) of 34-, 50-, and 64-kt winds at 0, 12, 24, and 36 hours, and radii of 34- and 50-kt winds at 48 and 72 hours Likelihood of TC formation within 48 hours Storm surge (beginning this year, inundation levels) Rainfall (HPC), Tornadoes (SPC)

5 WHAT WE MAY FORECAST IN FUTURE YEARS Track: center positions out to 7 days Intensity: out to 7 days? Size/Structure: additional radii (by quadrant) of 34-, 50-, and 64-kt winds beyond 36 hours? Full 2-d distribution of surface winds? Likelihood of TC formation beyond 48 hours Track/intensity forecasts for TCs that have not yet formed More detailed storm surge (including waves at the coast), rainfall, and tornado(?) information

6 2008 Atlantic Verification (courtesy of James Franklin, NHC) VT NT TRACK INT (h) (n mi) (kt) ============================ Values in green exceed alltime records. * 48 h track error for TS and H only (GPRA goal) was 87.5 n mi, just off last year s record of 86.2.

7 Atlantic Track Error Trends Errors have been cut in half over the past 15 years was best year ever.

8 2008 Track Guidance Official forecast performance was very close to the consensus models. Best model was ECMWF, which was so good that it was as good or better than the consensus. BAMD was similar to the poorest of the 3-D models (UKMET). AEMI excluded due to insufficient availability (less than 67% of the time at 48 or 120 h).

9 2008 Track Guidance Examine major dynamical models to increase sample size. ECMWF best at all time periods (as opposed to last year, when it was mediocre). GFDL also better than last year (and better than HWRF). As we ve seen before, GFDL skill declines relatively sharply at days 4-5. NOGAPS and GFNI again performed relatively poorly. Planned GFNI upgrades for 2008 were delayed.

10 GFDL-HWRF Comparison Much larger sample than last year shows that the HWRF is competitive with, but has not quite caught up to the GFDL yet. Consensus of the two (mostly) better than either alone.

11 Guidance Trends Return to more traditional relationships among the models after the very limited sample of 2007.

12 Guidance Trends Relative performance at 120 h is more variable, although GFSI has been strong every year except GFDL is not a good performer at the longer ranges.

13 Consensus Models Best consensus model was TVCN, the variable member consensus that includes EMXI. It does not appear that the correction process was beneficial.

14 Atlantic Intensity Error Trends No progress with intensity.

15 2008 Intensity Guidance OFCL adds most value over guidance at shorter ranges. Modest high bias in 2008 (2007 was a low bias). Split decision between the dynamical vs statistical models. New ICON consensus, introduced this year, was very successful, beating OFCL except at 12 h.

16 2008 Intensity Guidance HWRF competitive through 3 days, with issues at the longer times. Although the sample was smaller, there was a hint of this last year as well. Cannot shut GFDL off yet!

17 2008 Intensity Guidance When the complication of timing landfall/track dependence is removed, OFCL performs better relative to the guidance. Dynamical models are relatively poor performers.

18 DYNAMICAL MODELS NEED TO IMPROVE ON FORECASTING RAPID INTENSIFICATION AND RAPID WEAKENING -- AND CONSISTENCY GFDL HWRF CARIBBEAN HURRICANE PALOMA, NOVEMBER 2008: HWRF DID A LITTLE BETTER JOB THAN GFDL FOR INTENSIFICATION AND WEAKENING. HOWEVER BOTH MODELS HAVE BEEN INCONSISTENT.

19 WHAT ELSE SHOULD WE BE VERIFYING? 6- and 7-day predictions of track and intensity (model forecasts) Four-quadrant wind radii (official and model forecasts); note that additional investigation is needed before NHC formally verifies official wind radii forecasts Two-d distribution of the surface wind field (model forecasts) Three-d mass/motion structure (model forecasts) RMW, eye size (model forecasts) Convective distribution, asymmetries (model forecasts) Genesis, and tracks of TCs after genesis

20 Genesis Forecast Verification

21 SERIES OF GFS FORECASTS VERIFYING NEAR OF GENESIS OF BERTHA

22 SERIES OF GFS FORECASTS VERIFYING NEAR OF GENESIS OF GUSTAV

23 Track Guidance and NHC Forecasts Failed to Accurately Predict Hanna s Loop Between the Turks & Caicos Islands and Hispaniola NHC Forecasts HWFI EMXI GFSI GFDI UKMI

24 DYNAMICAL TRACK MODEL GUIDANCE FOR HURRICANE IKE 9/5/ UTC GFS & OFFICIAL FORECAST ECMWF

25 Ike: ECMWF representation, showing a vertically very deep vortex that would respond to upper-level steering

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27 Ike: GFS representation, showing a vertically shallower vortex that would be steered by the low- to mid-level flow

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29 ONE SHOULD NOT FOCUS ON THE EXACT 4 AND 5 DAY FORECAST POSITIONS BECAUSE LARGE UNCERTAINTIES EXIST AT THOSE TIMES.

30 ARE SINGLE MODEL ENSEMBLES USEFUL?

31 Consensus Models Third year in a row AEMI trailed the control run. Multimodel ensembles remain far more effective for TC forecasting. ECMWF ensemble mean is also not as good as the control run (EEMN v EMX).

32 HURRICANE IKE BEST TRACK

33 HURRICANE IKE BEST TRACK & GFS 9/8/08 12Z

34 HURRICANE IKE BEST TRACK, GFS, & GFS ENSEMBLE 9/8/08 12Z

35 HURRICANE IKE BEST TRACK, GFS, GFS ENSEMBLE, & ENSEMBLE MEAN 9/8/08 12Z

36 HURRICANE IKE BEST TRACK, DYNAMICAL MODELS, GFS ENSEMBLE MEAN, AND OFFICIAL FORECAST 9/9/08 00Z

37 NHC Tropical Cyclone Discussion Forecaster Pasch HURRICANE IKE BEST TRACK, GFS, GFS ENSEMBLE MEAN, MULTI MODEL CONSENUS, AND OFFICIAL FORECAST 9/9/08 00Z

38 WHAT WE NEED (not a complete list!) Increased model diagnostics activities Focus on infamous cases for track/intensity forecasts More guidance on guidance, e.g. selective consensus More model diagnostics tools for 4-d structural analyses, e.g. point and click cross sections 3-d trajectory analysis Budget studies Quality/fidelity of initialization; ability to analyze how well model assimilates observations of interest Forecaster-specified layer to layer shear analysis Center locations at multiple vertical levels; depiction of vertical coherence Calculations of metrics/measures of forecast reliablility Genesis probabilities derived from ensemble forecasts of global ensembles and possibly high-res pre-tc models

39 THANK YOU FOR YOUR ATTENTION NOAA/NESDIS