Application of T382 CFS Forecasts for Application of T382 CFS Forecasts for Dynamic Hurricane Season PredictionDynamic Hurricane Season Prediction

J. Schemm, L. Long, S. Saha and J. Schemm, L. Long, S. Saha and S. MoorthiS. Moorthi

NOAA/NWS/NCEPNOAA/NWS/NCEP

October 21, 2008October 21, 2008The 33rd Climate Diagnostics and Prediction Workshop, The 33rd Climate Diagnostics and Prediction Workshop,

Lincoln, NELincoln, NE

OutlineOutline

Description of the CFS experimentDescription of the CFS experiment Datasets UsedDatasets Used IRI Detection and Tracking Method IRI Detection and Tracking Method Analysis of storm activity statisticsAnalysis of storm activity statistics Focus on the Atlantic BasinFocus on the Atlantic Basin

• StatisticsStatistics• A look at CFS predictions for 2008A look at CFS predictions for 2008

Future planFuture plan

CFS T382 hurricane season experiments

1. One of the FY07/08 CTB internal projects

2. AGCM - 2007 operational NCEP GFS in T382/L64 resolutionLSM - Noah LSMOGCM - GFDL MOM3

3. All runs initialized with NCEP/DOE R2 and NCEP GODAS.Initial conditions at 0Z, Apr. 19, 20, (21) and May 15(FY07) for 1981-2007. Forecasts extended to December 1.

4. For May 15 cases, runs in T62 and T126 resolutions also performed.

DatasetsDatasets CFS hindcasts at T382CFS hindcasts at T382

• May 15May 15thth Initial Condition Initial Condition Output at every 3 hours Output at every 3 hours 1981-2007, 27 years 1981-2007, 27 years

• April 19April 19thth and April 20 and April 20thth Initial Condition Initial Condition Output at every 6 hours Output at every 6 hours 1981-2008, 28 years1981-2008, 28 years More appropriate ICs for CPC Operational More appropriate ICs for CPC Operational

Hurricane Season OutlookHurricane Season Outlook Observations from the HURDAT and JTWC Best Observations from the HURDAT and JTWC Best

Track DatasetTrack Dataset• -Tropical depressions and subtropical storms-Tropical depressions and subtropical storms• are not included in storm counts.are not included in storm counts.

Tropical Cyclone Detection MethodTropical Cyclone Detection Method Based on method devised by Camargo and Based on method devised by Camargo and

Zebiak (2002) at IRIZebiak (2002) at IRI Detection algorithm uses basin-dependent Detection algorithm uses basin-dependent

threshold criteria for three variablesthreshold criteria for three variables• VorticityVorticity, , threshthresh

thresh thresh = 2= 2

• 10-m Wind Speed10-m Wind Speed, , threshthresh

thresh thresh = = glgl + + glgl = wind speed averaged over= wind speed averaged over all global basinsall global basins

• Vertically integrated temp anomaly,Vertically integrated temp anomaly, T Tthreshthresho TTthresh thresh = = TT/2/2 o Calculated using only warm-core systemsCalculated using only warm-core systems

1.1. 850-hPa relative vorticity >850-hPa relative vorticity > threshthresh

2.2. Maximum 10-m wind speed in a 7x7 box >Maximum 10-m wind speed in a 7x7 box > threshthresh

3.3. SLP is the minimum in the centered 7x7 boxSLP is the minimum in the centered 7x7 box4.4. Temp anomaly averaged over the 7x7 box and three Temp anomaly averaged over the 7x7 box and three

pressure levels (300, 500, & 700 mb) > Tpressure levels (300, 500, & 700 mb) > Tthreshthresh

5. 5. Temperature anomaly averaged over the 7x7 box is Temperature anomaly averaged over the 7x7 box is positive at all levels (300, 500, & 700 mb) *positive at all levels (300, 500, & 700 mb) *

6.6. Temperature anomaly averaged over the 7x7 box at Temperature anomaly averaged over the 7x7 box at 300mb > 850mb *300mb > 850mb *

7.7. Wind speed averaged over the 7x7 box at 850mb > Wind speed averaged over the 7x7 box at 850mb > 300mb300mb

8.8. The storm must last for at least 6 hours.The storm must last for at least 6 hours. * Criteria 5 & 6 define a warm core system.* Criteria 5 & 6 define a warm core system.

Eight conditions must be met for a point to be Eight conditions must be met for a point to be considered a tropical cycloneconsidered a tropical cyclone

Storm TrackingStorm Tracking Once a point is designated as a tropical cyclone, the Once a point is designated as a tropical cyclone, the

cyclone is tracked forward and backward in time to create a cyclone is tracked forward and backward in time to create a full storm track.full storm track.

The maximum vorticity in a 5x5 grid around the cyclone is The maximum vorticity in a 5x5 grid around the cyclone is found and a new 3x3 box is formed around it. found and a new 3x3 box is formed around it.

At the next time step, if the maximum vorticity in this new At the next time step, if the maximum vorticity in this new box is greater than 3.5 x 10box is greater than 3.5 x 10-5-5 s s-1-1, the procedure is repeated. , the procedure is repeated.

This point has become part of the storm track.This point has become part of the storm track. If two storm tracks are the same, they are considered the If two storm tracks are the same, they are considered the

same cyclone and counted as one.same cyclone and counted as one.

Four NH Ocean BasinsFour NH Ocean Basins

Western North Pacific North Indian

Atlantic Eastern North Pacific Examples of Storm Tracks for 4 NH BasinsExamples of Storm Tracks for 4 NH Basins

AtlanticAtlanticBasinBasin

Atlantic Tropical Storms

EasternEasternPacificPacificBasinBasin

Eastern Pacific Tropical Storms

JJA Nino 3.4 SST IndexJJA Nino 3.4 SST Index

0.722IC=04190.671IC=0420

0.872IC=0515R2T382

JJA Atlantic MDR SST IndexJJA Atlantic MDR SST Index

0.629IC=04190.624IC=0420

0.781IC=0515R2T382

OBS IC=0515

IC=0419 IC=0420

Tropical Storm Origins, 1981-2007 ASOTropical Storm Origins, 1981-2007 ASO

Atlantic Basin CorrelationsAtlantic Basin Correlations

0.080.850.550.400.180.35IC=05150.30-0.390.320.330.33IC=0420

0.510.160.860.14-0.100.44IC=0419NeutralLa NinaEl Nino94-0681-93Total 

N=27 N=13 N=13 N=8 N=5 N=14

Red = Statistically Significant at 0.95 Correlations based on 27-year anomaly

0.79

Anomalies of Atlantic Storms

0.370.800.520.690.610.66IC=05150.49 0.220.150.700.58IC=04200.350.650.740.230.050.47IC=0419

NeutralLa NinaEl Nino94-0681-93Total Correlations

Red = Statistically Significant at 0.95

0.90

2008 Atlantic Season Summary

ObsNOAA

OutlookOutlook

Update

CFS-StatMay

CFS-StatUpdate

Named Storm 15 12-16 14-18 9-16 13-16

Hurricane 7 6-9 7-10 5-9 7-10

Major

Hurricane 4 2-5 3-6 2-4 3-5

As of October 17, 2008

Atlantic Basin Prediction for 2008Atlantic Basin Prediction for 2008

Two additional runs were made using July Two additional runs were made using July 1515thth and 16 and 16thth initial conditions for 2008 initial conditions for 2008 onlyonly

Used as a trial run for the CPC Hurricane Used as a trial run for the CPC Hurricane Outlook UpdateOutlook Update

13.330.67132.333.671.33 1ENSM

1612841071693420715

154431Obs

111333104221524233104211411235110419

TotalNovOctSepAugJulJunMay2008

Atlantic BasinAtlantic BasinCFS 2008 Monthly Storm CountCFS 2008 Monthly Storm Count

3

(Courtesy of Unisys)

Large number of storms over the Gulf of Mexico this year

2008 Atlantic Storm Tracks

Resemble Bertha and Cristobal

.Summary

CFS in T382 resolution exhibits robust climatological seasonal cycle of tropical cyclone over four NH basins.

Warming trend and intensification of hurricane activity in the Atlantic basin captured in the CFS hindcasts.

Fair level of skill in predicting interannual variability of seasonal storm activities based on the limited number of forecast runs.

Continue to increase number of ensemble members for better climatology and storm statistics. Hope to provide input for 2009 Hurricane Season Outlook with real time prediction runs.

Prospect of multi-model ensemble approach for dynamical hurricane season prediction