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Tropical cyclone activity and forecasts - March 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 2 5 7
 
Name Identifier Basin Start Date End Date 1-minute MSW 10-minute MSW
Japhet 19S SWI 26 February 03 March 115 100
Graham 20S AUS 27 February 01 March 35 55
Harriet 21S AUS 02 March 09 March 35 55
Erica 22P AUS 04 March 15 March 140 115
Kalunde 23S SWI 04 March 15 March 140 115
Craig 24S AUS 09 March 12 March 35 55
Eseta 25P AUS 10 March 14 March 110 95

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

None.

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: JAPHET Identifier: 19S
Basin: SOUTH-WEST INDIAN
Start date: 26.02.2003 End date: 03.03.2003
1-minute MSW: 115 knots 10-minute MSW: 100 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 -1 -14 -118 -192 -228 ****
Mean DY 1 92 125 130 33 ****
Mean AT -16 -49 -108 57 138 ****
Mean CT -3 -23 92 221 180 ****
Track skill (%) **** 25 41 57 **** ****
Mean DPE 38 149 270 300 227 ****
2001-2 DPE * 45 186 300 388 487 624
Intensity skill (%) **** 71 60 100 100 ****

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

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

Track forecast errors were below last season's average and skill scores against CLIPER were high. Early forecasts of landfall were a little too fast.

 

Name: GRAHAM Identifier: 20S
Basin: AUSTRALIAN (SE Indian)
Start date: 27.02.2003 End date: 01.03.2003
1-minute MSW: 35 knots 10-minute MSW: 55 knots

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 4 2 0 0 0 0
Detection Rate (%) 100 100 **** **** **** ****
Mean DX -13 -42 **** **** **** ****
Mean DY 6 78 **** **** **** ****
Mean AT 9 52 **** **** **** ****
Mean CT 26 -60 **** **** **** ****
Track skill (%) **** 68 **** **** **** ****
Mean DPE 69 88 **** **** **** ****
2001-2 DPE * 55 180 268 407 366 ****
Intensity skill (%) **** 100 **** **** **** ****

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

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

Only two forecasts were verified for this storm. Their average track forecast errors were small and landfall well predicted.

 

Name: HARRIET Identifier: 21S
Basin: AUSTRALIAN (SE Indian)
Start date: 02.03.2003 End date: 09.03.2003
1-minute MSW: 35 knots 10-minute MSW: 55 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 7 -12 -14 98 160 -186
Mean DY -3 7 87 220 363 67
Mean AT -19 -38 17 -19 77 182
Mean CT 13 -1 53 228 403 -61
Track skill (%) **** 44 52 47 **** ****
Mean DPE 29 111 142 247 414 193
2001-2 DPE * 55 180 268 407 366 ****
Intensity skill (%) **** 11 -14 -60 -33 -100

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

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

Track forecast errors were below last season's average at al times except T+96 and skill scores were high. Nearly all forecasts correctly predicted the storm's south-westward turn which prevented landfall occurring.

 

Name: ERICA Identifier: 22P
Basin: AUSTRALIAN (SW Pacific)
Start date: 04.03.2003 End date: 15.03.2003
1-minute MSW: 140 knots 10-minute MSW: 115 knots

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 14 10 6 3 1 2
Detection Rate (%) 100 100 100 100 100 100
Mean DX -26 -97 -162 -309 -352 -321
Mean DY 15 22 -62 -215 78 445
Mean AT -22 -139 -231 -381 -254 183
Mean CT -19 -56 12 7 -252 -514
Track skill (%) **** 46 49 40 **** ****
Mean DPE 53 177 245 427 358 546
2001-2 DPE * 55 180 268 407 366 ****
Intensity skill (%) **** 40 33 -100 100 ****

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

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

Erica dissipated within two days of forming, but then regenerated into an intense cyclone a few days later further to the north. Track forecast errors were near to last season's average overall and skill scores against CLIPER were high. The cyclone accelerated rapidly near the end of its life and forecasts were generally too slow.

 

Name: KALUNDE Identifier: 23S
Basin: SOUTH-WEST INDIAN
Start date: 04.03.2003 End date: 15.03.2003
1-minute MSW: 140 knots 10-minute MSW: 115 knots

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 21 19 17 15 13 11
Detection Rate (%) 100 100 100 100 100 100
Mean DX -8 -47 -148 -234 -298 -328
Mean DY 11 80 56 5 -115 -182
Mean AT 14 81 79 35 -140 -265
Mean CT -2 6 -83 -132 -164 -222
Track skill (%) **** 2 12 -8 **** ****
Mean DPE 31 120 187 301 423 483
2001-2 DPE * 45 186 300 388 487 624
Intensity skill (%) **** 79 65 60 23 -27

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

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

Track forecast errors were below last season's average for this cyclone. Skill scores against CLIPER were modest. Some forecasts did not forecast the southward turn of the cyclone, although others did.

 

Name: CRAIG Identifier: 24S
Basin: AUSTRALIAN (Arafura Sea)
Start date: 09.03.2003 End date: 12.03.2003
1-minute MSW: 35 knots 10-minute MSW: 55 knots

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 7 5 3 1 0 0
Detection Rate (%) 100 100 100 100 **** ****
Mean DX --20 -66 -22 -11 **** ****
Mean DY -9 29 26 78 **** ****
Mean AT -14 -57 -19 4 **** ****
Mean CT 5 -35 -27 -80 **** ****
Track skill (%) **** 27 81 **** **** ****
Mean DPE 42 158 98 81 **** ****
2001-2 DPE * 55 180 268 407 366 ****
Intensity skill (%) **** 60 33 100 **** ****

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

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

The formation of Craig was well predicted and the forecasts verified were also good. Track forecast errors were low and skill scores high.

 

Name: ESETA Identifier: 25P
Basin: AUSTRALIAN (SW Pacific)
Start date: 10.03.2003 End date: 14.03.2003
1-minute MSW: 110 knots 10-minute MSW: 95 knots

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 7 5 3 1 0 0
Detection Rate (%) 100 100 100 100 **** ****
Mean DX -42 -223 -361 -669 **** ****
Mean DY -14 -67 19 -245 **** ****
Mean AT -54 -236 -339 -715 **** ****
Mean CT 4 13 -89 -20 **** ****
Track skill (%) **** 42 **** **** **** ****
Mean DPE 65 247 367 716 **** ****
2001-2 DPE * 55 180 268 407 366 ****
Intensity skill (%) **** 20 33 100 **** ****

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

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

Eseta was a fast-moving storm and track forecast errors were above last season's average due to a slow bias.

 

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:- 7
Number of storms used in statistics below:- 7

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 76 59 42 28 18 14
Detection Rate (%) 100 100 100 100 100 100
Mean DX 4 -48 -122 -186 -221 -387
Mean DY 4 41 46 27 -17 -75
Mean AT -11 -33 -38 -45 -95 -169
Mean CT 0 -15 -21 -9 -55 -253
Track skill (%) **** 32 40 27 **** ****
Mean DPE 42 146 208 312 407 471
2001-2 DPE * 48 184 264 390 480 624
Intensity skill (%) **** 77 64 67 29 -27

* DPE for all Southern Hemisphere storms in 2001-2 season

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

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

On the whole, track forecast errors were below last season's average this month and skill scores against CLIPER were high. There was a slow bias in forecasts. The overall intensity tendency skill score was 52%.