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Tropical cyclone activity and forecasts - February 2008

Tropical cyclone activity

Tropical cyclones ending during the month
  NWP NEP NAT NI SWI AUS Total
Total number ending during the month 0 0 0 0 4 3 7
 
Tropical cyclones active during the month
Name Identifier Basin Start date End date 1-minute MSW 10-minute MSW
Fame 13S SWI 25 January 01 February 80 60
Gula 14S SWI 27 January 02 February 85 85
Gene 15P AUS 27 January 06 February 90 85
Hondo 16S SWI 04 February 24 February 125 115
- 17S AUS 07 February 10 February 40 30
Ivan 18S SWI 07 February 21 February 115 100
Nicholas 19S AUS 13 February 20 February 80 80

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.

Tropical cyclones still active at the end of the month

Tropical cyclones active during the month
Name Identifier Basin Start date
- 20P AUS 28 February
Ophelia 21S AUS 29 February

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 that 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 0.5625°x 0.375°x 50 levels. This is equivalent to a horizontal resolution of 62km x 42km at the equator.

Individual tropical cyclone summaries

Name: FAME Identifier: 13S
Basin: SOUTH-WEST INDIAN
Start date: 27.01.2008 End date: 01.02.2008
1-minute MSW: 80 knots 10-minute MSW: 60 knots

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 5 3 1 0 0 0
Detection Rate (%) 100 100 100 **** **** ****
Mean  DX     37 -28 -275 **** **** ****
Mean  DY  -15 7 111 **** **** ****
Mean   AT -1 1 -26 **** **** ****
Mean   CT 32 -15 -294 **** **** ****
Track skill (%) **** 34 **** **** **** ****
Mean DPE 52 94 296 **** **** ****
2006-07 DPE * 54 130 283 458 665 802
Intensity skill (%) **** 33 100 **** **** ****

* DPE for all storms in the 2006-7 season in the SWI basin

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

Fame was a tropical storm for a fairly brief period. One 48-hour forecast and three 24-hour forecasts were verified.

 

Name: GULA Identifier: 14S
Basin: SOUTH-WEST INDIAN
Start date: 27.01.2008 End date: 02.02.2008
1-minute MSW: 85 knots 10-minute MSW: 85 knots

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 12 10 8 6 4 2
Detection Rate (%) 100 100 100 100 100 100
Mean  DX     -1 -34 -56 -251 -217 -284
Mean  DY  -6 31 0 -148 -261 -445
Mean   AT -11 -4 9 -77 -133 -385
Mean   CT -1 28 12 -248 -268 -358
Track skill (%) **** 61 66 40 **** ****
Mean DPE 83 116 193 474 375 538
2006-07 DPE * 54 130 283 458 665 802
Intensity skill (%) **** -40 -25 -33 -50 0

* DPE for all storms in the 2006-7 season in the SWI basin

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

Track forecast errors were generally below last season’s average for this storm. Skill scores were very high. There was a slow and right-of-track bias in longer lead time forecasts.

 

Name: GENE Identifier: 15P
Basin: AUSTRALIAN (S Pacific)
Start date: 27.01.2008 End date: 06.02.2008
1-minute MSW: 90 knots 10-minute MSW: 85 knots

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 19 17 15 13 11 9
Detection Rate (%) 100 100 100 100 100 100
Mean  DX     -5 -25 -109 -254 -651 -1022
Mean  DY  21 8 -39 -58 -50 -40
Mean   AT -8 -9 40 -16 -290 -617
Mean   CT 6 12 -13 -235 -326 -407
Track skill (%) **** 18 -32 -109 **** ****
Mean DPE 79 106 243 437 765 1110
2006-07 DPE * 72 153 355 665 1075 1537
Intensity skill (%) **** 29 7 23 -9 33

* DPE for all storms in the 2006-7 season in the AUS basin

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

The model initially failed to predict the recurvature of Gene and long lead time track errors were large. However, they were still below last year’s average due to the poor performance in this region last year. Skill scores were only positive at T+24.

 

Name: HONDO Identifier: 16S
Basin: SOUTH-WEST INDIAN
Start date: 04.02.2008 End date: 24.02.2008
1-minute MSW: 125 knots 10-minute MSW: 155 knots

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 14 12 10 8 6 4
Detection Rate (%) 100 100 100 100 100 100
Mean  DX     -10 -55 -63 -14 75 331
Mean  DY  -9 -5 -74 -121 -187 -284
Mean   AT -13 -47 -66 -31 32 227
Mean   CT 8 -46 -66 -31 32 227
Track skill (%) **** 31 49 65 **** ****
Mean DPE 36 82 153 167 228 448
2006-07 DPE * 54 130 283 458 665 802
Intensity skill (%) **** 50 60 50 33 -50

* DPE for all storms in the 2006-7 season in the SWI basin

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

Hondo was well forecast whilst at tropical storm intensity (or greater). Track errors were low and skill scores high. The abrupt turn of the remnant low to the west was also well predicted and although it never regained tropical storm strength according to RSMC La Reunion, this portion of the track was fairly well forecast (although not verified).

 

Name: Identifier: 17S
Basin: AUSTRALIAN (SE Indian)
Start date: 07.02.2008 End date: 10.02.2008
1-minute MSW: 40 knots 10-minute MSW: 30 knots

There are no verification statistics or forecast plot for this tropical cyclone since its 10-minute averaged winds did not reach tropical storm strength

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

 

Name: IVAN Identifier: 18S
Basin: SOUTH-WEST INDIAN
Start date: 07.02.2008 End date: 21.02.2008
1-minute MSW: 115 knots 10-minute MSW: 100 knots

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 20 18 16 14 12 10
Detection Rate (%) 100 100 100 100 100 100
Mean  DX     -7 -101 -267 -336 -367 -258
Mean  DY  -7 69 120 203 249 355
Mean   AT 9 25 150 237 354 312
Mean   CT 6 47 72 139 227 333
Track skill (%) **** -8 -10 6 **** ****
Mean DPE 41 138 311 419 474 503
2006-07 DPE * 54 130 283 458 665 802
Intensity skill (%) **** 33 25 43 0 -20

* DPE for all storms in the 2006-7 season in the SWI basin

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

The westward movement of Ivan was initially predicted to occur sooner than it did. Track forecast errors were near to or below last season’s average, although track skill scores were not good.

 

Name: NICHOLAS Identifier: 19S
Basin: AUSTRALIAN (SE Indian)
Start date: 13.02.2008 End date: 20.02.2008
1-minute MSW: 80 knots 10-minute MSW: 80 knots

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 15 13 11 9 7 5
Detection Rate (%) 100 100 100 100 100 100
Mean  DX     -1 16 120 276 373 475
Mean  DY  -14 53 79 131 222 240
Mean   AT 1 -11 -48 -110 -48 49
Mean   CT 11 38 110 271 370 450
Track skill (%) **** 30 8 11 **** ****
Mean DPE 53 100 160 322 442 551
2006-07 DPE * 72 153 355 665 1075 1537
Intensity skill (%) **** 54 82 33 71 20

* DPE for all storms in the 2006-7 season in the AUS basin

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

Forecasts for Nicholas had a persistent leftward bias resulting in landfall too soon. Despite this, Track forecast errors were not particularly high. There was modest skill over CLIPER.

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: 6

MEAN ERROR STATISTICS
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 85 73 61 50 40 30
Detection Rate (%) 100 100 100 100 100 100
Mean  DX -2 -43 -97 -143 -234 -288
Mean  DY -3 32 26 28 46 79
Mean   AT -3 -6 22 10 -23 -145
Mean   CT 7 17 22 -8 21 70
Track skill (%) **** 28 21 15 **** ****
Mean DPE 57 110 225 372 502 688
2006-7 DPE * 54 136 298 496 727 870
Intensity skill (%) **** 29 31 28 10 0

* DPE for all southern hemisphere storms in 2006-7 season

Track forecast errors were below last season’s average and skill scores modestly positive this month. Although some storms exhibited track biases, these tended to cancel each other out in the averaged figure for the whole month. The overall intensity tendency skill score was 23%.