Tropical cyclone activity and forecasts - April 2007
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 | 1 | 0 | 0 | 0 | 1 | 1 | 3 |
| Name | Identifier | Basin | Start date | End date | 1-minute MSW | 10-minute MSW |
|---|---|---|---|---|---|---|
| Jaya | 22S | SWI | 30 March | 04 April | 110 | 90 |
| Kong-rey | 01W | NWP | 31 March | 05 April | 90 | 75 |
| Cliff | 23P | AUS | 04 April | 06 April | 55 | 50 |
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 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.
2.1 Individual tropical cyclone summaries
Name: JAYA Identifier: 22S
Basin: SOUTH-WEST
INDIAN
Start date: 30.03.2007 End
date: 04.04.2007
1-minute MSW: 110 knots
10-minute MSW: 90 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
|---|---|---|---|---|---|---|
| Possibly verified | 10 | 7 | 5 | 3 | 1 | 0 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | **** |
| Mean DX | 8 | 61 | 69 | -18 | 292 | **** |
| Mean DY | 52 | 76 | 104 | 52 | -122 | **** |
| Mean AT | -17 | -65 | -73 | -7 | -222 | **** |
| Mean CT | 53 | 74 | 93 | 80 | -228 | **** |
| Track skill (%) | **** | 19 | 66 | 75 | **** | **** |
| Mean DPE | 69 | 116 | 169 | 189 | 319 | **** |
| 2005-6 DPE * | 62 | 149 | 202 | 353 | 554 | 697 |
| Intensity skill (%) | **** | 43 | 60 | 100 | -100 | **** |
* DPE for all storms in the 2005-6 season in the SWI basin
 |
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. There was a slight slow bias in forecasts.
Name: KONG-REY Identifier: 01W
Basin: NORTH-WEST PACIFIC
Start date: 31.03.2007 End
date: 05.04.2007
1-minute MSW: 90 knots 10-minute
MSW: 75 knots
| 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 | 2 | -48 | 33 | 118 | -532 | **** |
| Mean DY | -22 | 51 | 187 | 200 | -345 | **** |
| Mean AT | -38 | -1 | 178 | 276 | -638 | **** |
| Mean CT | 15 | -3 | -105 | -240 | 10 | **** |
| Track skill (%) | **** | 19 | 40 | 25 | **** | **** |
| Mean DPE | 54 | 188 | 293 | 532 | 845 | **** |
| 2006 DPE * | 60 | 114 | 204 | 304 | 422 | 551 |
| Intensity skill (%) | **** | 50 | 0 | 50 | 100 | **** |
* DPE for all storms in the 2006 season in the NWP basin
 |
Plot of the storm's observed track and forecasts |
Track forecast errors were higher than last season’s average, although the model showed skill over CLIPER. Biases were variable in sign.
Name:CLIFF Identifier: 23P
Basin: AUSTRALIAN (S Pacific)
Start date: 04.04.2007 End date: 06.04.2007
1-minute MSW: 55 knots 10-minute MSW:50 knots
| 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 | -23 | -26 | **** | **** | **** | **** |
| Mean DY | -3 | -28 | **** | **** | **** | **** |
| Mean AT | -19 | -44 | **** | **** | **** | **** |
| Mean CT | -8 | 1 | **** | **** | **** | **** |
| Mean DPE | 51 | 51 | **** | **** | **** | **** |
| 2005-6 DPE * | 69 | 136 | 252 | 391 | 561 | 495 |
| Intensity skill (%) | **** | 0 | **** | **** | **** | **** |
* DPE for all storms in the 2005-6 season in the AUS basin
 |
Plot of the storm's observed track and forecasts |
Cliff was a short-lived storm and only two 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: 3
Number of storms used in statistics below: 3
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
|---|---|---|---|---|---|---|
| Possibly verified | 24 | 17 | 11 | 7 | 3 | 0 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | **** |
| Mean DX | 0 | 0 | 49 | 60 | -257 | **** |
| Mean DY | 12 | 52 | 150 | 137 | -270 | **** |
| Mean AT | -27 | -32 | 63 | 155 | -499 | **** |
| Mean CT | 27 | 29 | -15 | -103 | -69 | **** |
| Track skill (%) | **** | 19 | 49 | 40 | **** | **** |
| Mean DPE | 60 | 142 | 236 | 385 | 669 | **** |
| 2005-6 DPE * | 67 | 140 | 237 | 379 | 559 | 571 |
| Intensity skill (%) | **** | 41 | 27 | 71 | 33 | **** |
* DPE for all southern hemisphere storms in 2005-06 season
Comments:
There were just three storms this month, so the number of forecasts verified was relatively small. No T+120 forecasts were verified. Track forecast errors were near to last season’s values except at T+96. Skill scores against CLIPER were positive. The overall intensity tendency skill score was 42%.
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