Tropical cyclone activity and forecasts - February 2003

1. Tropical cyclone activity

1.1 Tropical cyclones ending during the month

NWP NEP NAT NI SWI AUS TOTAL Total number ending during the month 0 0 0 0 3 2 5

 

Name Identifier Basin Start Date End Date 1-minute MSW 10-minute MSW Fiona 14S AUS 05 February 13 February 100 110 Dovi 15P AUS 15 February 10 February 130 110 Gerry 16S SWI 08 February 15 February 105 90 Hape 17S SWI 09 February 15 February 80 70 Isha 18S SWI 11 February 14 February 45 35

Basin name abbreviations:-
NWP : North-West Pacific (west of 180°E)
NEP : North-East Pacific (east of 180°E)
NAT : North Atlantic
NI : North Indian (west of Malay Peninsula)
SWI : South-West Indian (west of 90°E)
AUS : Australian (east of 90°E)

1-minute MSW: Maximum sustained wind (knots) averaged over 1 minute (JTWC Hawaii, NHC Miami, CPHC Hawaii)
10-minute MSW: Maximum sustained wind (knots) averaged over 10 minutes (JMA Japan, southern hemisphere RSMCs and TCWCs)

Note: Although 1-minute average winds should be stronger than 10-minute average, this may not be the case here since estimates are obtained from different warning centres.

1.2 Tropical cyclones still active at the end of the month

Name Identifier Basin Start Date Japhet 19S SWI 26 February Graham 20S AUS 27 February

2. FORECAST ERROR STATISTICS

The Met Office global Numerical Weather Prediction model produces a 6-day forecast every 12 hours. The performance of the model in forecasting this month's tropical cyclones is assessed below. Mean error statistics for each storm which ended during the month are presented together with a final table of statistics for all storms ending this month. Verification is performed at 24 hour intervals up to forecast time T+120. Some mean error statistics for last year's storms are included for the purposes of a comparison. The present global model has a resolution of 0.83°x 0.55°x 39 levels. This is equivalent to a horizontal resolution of 93km x 62km at the equator.

2.1 Individual Tropical Cyclone Summaries

Name: FIONA Identifier: 14S
Basin: AUSTRALIAN (SE Indian)
Start date: 05.02.2003 End date: 13.02.2003
1-minute MSW: 100 knots 10-minute MSW: 110 knots

Table of Mean Error Statistics   T+0 T+24 T+48 T+72 T+96 T+120 Possibly Verified 16 14 12 10 8 6 Detection Rate (%) 100 100 100 100 100 67 Mean DX 9 -34 -71 -51 61 423 Mean DY -6 32 69 87 89 -222 Mean AT -6 34 65 32 -69 -376 Mean CT 1 2 -82 -197 -270 10 Track skill (%) **** 31 37 17 **** **** Mean DPE 33 113 227 358 461 499 2001-2 DPE * 55 180 268 407 366 **** Intensity skill (%) **** 14 33 60 75 100

* DPE for all storms in the 2001-2 season in the AUS basin

A plot of the storm's observed track and forecasts.

Track forecast errors for this storm up to T+72 were smaller than last season's average and skill scores were positive. There was a slight right-of-track bias at longer forecast ranges.

 

Name: DOVI Identifier: 15P
Basin: AUSTRALIAN (SE Pacific)
Start date: 05.02.2003 End date: 10.02.2003
1-minute MSW: 130 knots 10-minute MSW: 110 knots

Table of Mean Error Statistics   T+0 T+24 T+48 T+72 T+96 T+120 Possibly Verified 10 8 6 4 2 0 Detection Rate (%) 100 100 100 100 100 **** Mean DX -6 29 112 129 158 **** Mean DY 31 45 30 -11 -28 **** Mean AT 32 12 22 8 16 **** Mean CT -5 37 103 140 158 **** Mean DPE 46 105 179 187 160 **** 2001-2 DPE * 55 180 268 407 366 **** Intensity skill (%) **** 50 33 100 -100 ****

* DPE for all storms in the 2001-2 season in the AUS basin

A plot of the storm's observed track and forecasts.

Track forecasts for this storm were very good with errors well below last season's average. There was a slight left-of-track bias in forecasts

 

Name: GERRY Identifier: 16S
Basin: SOUTH-WEST INDIAN
Start date: 08.02.2003 End date: 15.02.2003
1-minute MSW: 105 knots 10-minute MSW: 90 knots

Table of Mean Error Statistics   T+0 T+24 T+48 T+72 T+96 T+120 Possibly Verified 11 9 7 5 3 1 Detection Rate (%) 100 100 100 100 100 100 Mean DX 4 -56 -141 -135 14 89 Mean DY 0 -4 -89 -165 -226 -122 Mean AT -12 -81 -156 -216 -166 28 Mean CT 2 -59 -53 36 225 145 Track skill (%) **** 32 52 58 **** **** Mean DPE 63 172 263 408 364 148 2001-2 DPE * 45 186 600 688 487 624 Intensity skill (%) **** 78 43 -20 -33 100

* DPE for all storms in the 2001-2 season in the SWI basin

A plot of the storm's observed track and forecasts.

Track forecast errors were near to or below last season's average for this storm. There was a slow bias in forecasts. Skill scores against CLIPER were very high.

 

Name: HAPE Identifier: 17S
Basin: SOUTH-WEST INDIAN
Start date: 09.02.2003 End date: 15.02.2003
1-minute MSW: 80 knots 10-minute MSW: 70 knots

Table of Mean Error Statistics   T+0 T+24 T+48 T+72 T+96 T+120 Possibly Verified 9 7 5 3 1 0 Detection Rate (%) 100 100 100 100 100 **** Mean DX -30 -103 -159 -247 -255 **** Mean DY -17 -9 98 170 478 **** Mean AT -41 -184 -204 -10 269 **** Mean CT 7 -31 -132 -296 -471 **** Track skill (%) **** 38 64 43 **** **** Mean DPE 60 206 297 350 543 **** 2001-2 DPE * 45 186 300 388 487 624 Intensity skill (%) **** 71 60 33 100 ****

* DPE for all storms in the 2001-2 season in the SWI basin

A plot of the storm's observed track and forecasts.

Track forecast errors were near to or slightly above last season's average for this storm, although skill scores were very high as it took a fairly unusual track. There was a right-of-track bias in forecasts.

 

Name: ISHA Identifier: 18S
Basin: SOUTH-WEST INDIAN
Start date: 11.02.2003 End date: 14.02.2003
1-minute MSW: 45 knots 10-minute MSW: 35 knots

Table of Mean Error Statistics   T+0 T+24 T+48 T+72 T+96 T+120 Possibly Verified 1 0 0 0 0 0 Detection Rate (%) 100 **** **** **** **** **** Mean DX -21 **** **** **** **** **** Mean DY -44 **** **** **** **** **** Mean AT -46 **** **** **** **** **** Mean CT 8 **** **** **** **** **** Mean DPE 47 **** **** **** **** **** 2001-2 DPE * 45 186 300 388 487 624

* DPE for all storms in the 2001-2 season in the SWI basin

A plot of the storm's observed track and forecasts.

Isha only briefly reached tropical storm status, so no forecasts were verified.

 

2.2 Summary of all Tropical Cyclones

Mean error statistics for all tropical cyclones (of at least tropical storm strength) which have ended this month are shown below.

Total number of depressions ending this month:- 5
Number of storms used in statistics below:- 5

Table of Mean Error Statistics   T+0 T+24 T+48 T+72 T+96 T+120 Possibly Verified 47 38 30 22 14 7 Detection Rate (%) 100 100 100 100 100 71 Mean DX -4 -39 -65 -64 42 356 Mean DY 0 18 29 23 33 -202 Mean AT -8 -38 -40 -35 -54 -295 Mean CT 1 -11 -47 -96 -117 37 Track skill (%) **** 34 49 40 **** **** Mean DPE 48 142 237 337 403 429 2001-2 DPE * 48 184 294 390 480 624 Intensity skill (%) **** 47 40 45 29 100

* Best track DPE for all southern hemisphere storms in 2001-2 season

A plot of the observed tracks of this month's storms in the South Indian Ocean.

A plot of the observed tracks of this month's storms in the Eastern Australian basin.

Track forecast errors for this month' storms were, on average, smaller than last season's average and skill scores against CLIPER were very good. There was a slight slow bias in forecasts. The overall intensity tendency skill score this month was a very good 45%.