SIX INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES 2006

IWTC-VI

SAN JOSE, COSTA RICA

NOVEMBER 2006

TOPIC 0.1

QUANTITATIVE FORECASTS OF TROPICAL CYCLONES LANDFALL IN RELATION TO AN EFFECTIVE WARNING SYSTEM: TRACK

FORECASTS

LIXION A. AVILA RSMC MIAMI

SIX INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES 2006

IWTC-VI

SAN JOSE, COSTA RICA

NOVEMBER 2006

TOPIC 0.1

WORKING GROUP:

PHILLIPE CAROFF, JEFF CALLAGHAN, JAMES FRANKLIN and

MARK DeMARIA

0

50

100

150

200

250

300

350

24-h 48-h 72-h 96-h 120-h

landfall

all storms

Average track forecast errors (nm) for the 1 to 5 day period before landfall (2001-2005)

RSMC LA REUNIONTime-evolution of

Cyclone tracks forecasts errors (5-years running means of direct position errors)

(All intensities)

1426 1515 1660 1619 1358 1344 1253 1211 1355 1522 1506

1035 1226 1483 1509 1288 1285 1214 1197 1332 1491 1476

495 532 568 657 664851 929 1132 1277 1435 1424

397435

470 484 411441 432 467 542 742 874

0

50

100

150

200

250

300

350

400

450

500

550

90/91 -94/95

91/92 -95/96

92/93 -96/97

93/94 -97/98

94/95 -98/99

95/96 -99/00

96/97 -00/01

97/98 -01/02

98/99 -02/03

99/00 -03/04

00/01 -04/05

analysis

12 h forecasts

24 h forecasts

48 h forecasts

0

100

200

300

400

500

600

700

19

65

19

70

19

75

19

80

19

85

19

90

19

95

20

00

20

05

Year

Mea

n F

ore

cast

Err

or

(nm

i)NHC64

NHC67

HURRAN

CLIPER

NHC72

NHC73

NHC83

NHC90

NWP-BAR

SANBAR

VICBAR

BAMD

LBAR

MFM

QLM

GFDL

GFS

UKMET

NOGAPS

OFCL

0

6

12

18

24

30

36

42

1963-1969 1970-1979 1980-1989 1990-1999 2000-2005

Time Interval

Ave

rag

e L

ead

Tim

e (h

r)

Average Lead Time of NHC Hurricane Warnings By Decade

Katrina Track ForecastsKatrina Track Forecasts1200 UTC 24 August1200 UTC 24 August

Katrina Track ForecastsKatrina Track Forecasts0000 UTC 27 August0000 UTC 27 August

Rita Track Forecasts Rita Track Forecasts 1200 UTC 21 September1200 UTC 21 September

Rita Track Forecasts Rita Track Forecasts 1200 UTC 21 September1200 UTC 21 September

Severe left bias in track modelsSevere left bias in track models

Rita Track ForecastsRita Track Forecasts1200 UTC 22 September1200 UTC 22 September

Rita Track ForecastsRita Track Forecasts1200 UTC 22 September1200 UTC 22 September

Remarkable improvement in track guidance: Likely the impact of surveillance data from the NOAA G-IV jet?

Remarkable improvement in track guidance: Likely the impact of surveillance data from the NOAA G-IV jet?

Ophelia Track Forecasts (nightmare)Ophelia Track Forecasts (nightmare) 1200 UTC 9 September 1200 UTC 9 September

Wilma Track Models10/21/05 18z

Navy GFDL 72 h

NCEP GFDL 72 h

U.K. Met. Office 72 h

GFS 72 h

NOGAPS 72 h

Verifying position 10/24/05 18z

Excellent example of GUNA consensus: HURRICANE ISABEL, 1200 UTC 11 SEP 2003Excellent example of GUNA consensus: HURRICANE ISABEL, 1200 UTC 11 SEP 2003

Not-so-excellent example of GUNA consensus:

HURRICANE KATE, 1800 UTC 29 SEP 2003

This is a case where forming a selective consensus can be effective.

Not-so-excellent example of GUNA consensus:

HURRICANE KATE, 1800 UTC 29 SEP 2003

This is a case where forming a selective consensus can be effective.

New Tropical Cyclone Wind Speed Probability Products from NHC

Richard Knabb, Chris Landsea, Edward Rappaport, Michelle Mainelli, Chris Lauer, Alison Krautkramer, James Franklin, and Jamie Rhome

National Hurricane Center

Scott Kiser and Tim Schott - NWS Headquarters

Mark DeMaria – NESDIS and John Knaff - CIRA

June 2006

Existing TPC/NHC Products Used to Convey Uncertainty

Watch/Warning Graphic

Indicates forecast track and long-term mean error

Need for improved means of conveying tropical cyclone forecast uncertainty to various types of users

– New product is about a weather event at any specific location

– Conveys chances of wind speeds of at least particular thresholds

• 34 kt (tropical storm force)• 50 kt• 64 kt (hurricane force)

– Accounts for combined uncertainty in track, intensity, and size

– Extends to 5 days– Includes inland locations– Replaced strike probabilities in 2006

Why a new probability product?

Challenges and Ongoing Work• Significant training and outreach needed

– Lessen the focus on exact track forecast– Do users understand probabilities?– Getting familiar with the probability values– “Small” probabilities of an extreme event

• Enhancements to graphical products– Faster creation of grids, and the graphics created from them

• Objective guidance for watch/warning breakpoints

• Eventual use by NWS forecast offices in their products

• Verification

• Gridded products for NDFD

• Discussion