Tropical cyclone activity
| Tropical cyclones ending during the month | |||||||
|---|---|---|---|---|---|---|---|
| NWP | NEP | NAT | NI | SWI | AUS | Total | |
| Total number ending during the month | 3 | 1 | 0 | 1 | 0 | 0 | 5 |
| Tropical cyclones active during the month | ||||||
|---|---|---|---|---|---|---|
| Name | Identifier | Basin | Start date | End date | 1-minute MSW | 10-minute MSW |
| Nargis | 01B | NI | 27 April | 03 May | 115 | 90 |
| Rammasun | 03W | NWP | 07 May | 13 May | 135 | 105 |
| Matmo | 04W | NWP | 14 May | 16 May | 40 | 45 |
| Halong | 05W | NWP | 15 May | 20 May | 70 | 60 |
| Alma | 01E | NEP | 29 May | 30 May | 55 | - |
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
| Name | Identifier | Basin | Start date |
| Nakri | 06W | NWP | 27 May |
| Arthur | 01L | NAT | 31 May |
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 62 km x 42 km at the equator.
Individual tropical cyclone summaries
Name: NARGIS Identifier: 01B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 27.04.2008 End date: 03.05.2008
1-minute MSW: 115 knots 10-minute MSW: 90 knots
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 13 | 11 | 9 | 7 | 5 | 3 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 15 | 0 | -35 | -77 | -190 | -479 |
| Mean DY | -18 | -63 | -162 | -195 | -178 | -363 |
| Mean AT | -9 | -84 | -92 | -167 | -237 | -585 |
| Mean CT | 14 | 24 | 84 | 151 | 197 | -57 |
| Track skill (%) | **** | 42 | 52 | 66 | **** | **** |
| Mean DPE | 56 | 125 | 239 | 336 | 419 | 708 |
| 2007 DPE * | 80 | 144 | 207 | 334 | 525 | 393 |
| Intensity skill (%) | **** | 27 | 33 | 14 | 20 | 33 |
* DPE for all storms in the 2007 season in the NI basin
A plot of the storm's observed track and forecasts
Forecasts for Cyclone Nargis were erratic in their quality. The 120-hour prediction of landfall was good, whereas the 96-hour forecast was poorer. This pattern was repeated for shorter lead time forecasts. Overall, track forecast errors were near to last season's average, although were large at the 5-day lead time. Skill scores against CLIPER were high. The model had a right of track bias, which meant that many forecast tracks took Nargis south of the Irrawaddy Delta of Burma. However, 24-36 hours ahead of landfall, the forecasts were good.
Name: RAMMASUN Identifier: 03W
Basin: NORTH-WEST PACIFIC
Start date: 07.05.2008 End date: 13.05.2008
1-minute MSW: 135 knots 10-minute MSW: 105 knots
| 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 | -38 | -120 | -215 | -371 | -1011 |
| Mean DY | 25 | 26 | -76 | -247 | -379 | -845 |
| Mean AT | 16 | 17 | -95 | -281 | -510 | -1323 |
| Mean CT | -24 | -42 | -89 | -90 | -105 | -53 |
| Track skill (%) | **** | 34 | 50 | 61 | **** | **** |
| Mean DPE | 63 | 88 | 182 | 334 | 533 | 1325 |
| 2007 DPE * | 63 | 133 | 199 | 279 | 407 | 513 |
| Intensity skill (%) | **** | 11 | 14 | 20 | -100 | -100 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of the storm's observed track and forecasts
Track forecast errors were near to last season's average at short lead times, but were large at longer lead times. This was due to early forecasts failing to predict the acceleration of the typhoon to the north-east as it started extra-tropical transition. Hence, there was a slow bias at longer lead times. However, skill scores against CLIPER were high.
Name: MATMO Identifier: 04W
Basin: NORTH-WEST PACIFIC
Start date: 14.05.2008 End date: 16.05.2008
1-minute MSW: 40 knots 10-minute MSW: 45 knots
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 2 | 0 | 0 | 0 | 0 | 0 |
| Detection Rate (%) | 100 | **** | **** | **** | **** | **** |
| Mean DX | 21 | **** | **** | **** | **** | **** |
| Mean DY | 78 | **** | **** | **** | **** | **** |
| Mean AT | 56 | **** | **** | **** | **** | **** |
| Mean CT | -43 | **** | **** | **** | **** | **** |
| Mean DPE | 96 | **** | **** | **** | **** | **** |
| 2007 DPE * | 63 | 133 | 199 | 279 | 407 | 513 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of the storm's observed track and forecasts
Matmo only briefly reached tropical storm status and no forecasts were verified.
Name: HALONG Identifier: 05W
Basin: NORTH-WEST PACIFIC
Start date: 15.05.2008 End date: 20.05.2008
1-minute MSW: 70 knots 10-minute MSW: 60 knots
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 8 | 6 | 4 | 2 | 0 | 0 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | **** | **** |
| Mean DX | 5 | -46 | -275 | -200 | **** | **** |
| Mean DY | -12 | 48 | -17 | 200 | **** | **** |
| Mean AT | -8 | -11 | -231 | -55 | **** | **** |
| Mean CT | 11 | -65 | -152 | -275 | **** | **** |
| Track skill (%) | **** | 12 | 51 | 75 | **** | **** |
| Mean DPE | 77 | 134 | 318 | 286 | **** | **** |
| 2007 DPE * | 63 | 133 | 199 | 279 | 407 | 513 |
| Intensity skill (%) | **** | 33 | 50 | 0 | **** | **** |
* DPE for all storms in the 2007 season in the NWP basin
A plot of the storm's observed track and forecasts
Track forecast errors were near to last season's average except at 48 hours lead time. There was a slight slow and left of track bias. Skill scores against CLIPER were high, particularly at longer lead times.
Name: ALMA Identifier: 01E
Basin: NORTH-EAST PACIFIC
Start date: 29.05.2008 End date: 30.05.2008
1-minute MSW: 55 knots 10-minute MSW: - knots
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 2 | 0 | 0 | 0 | 0 | 0 |
| Detection Rate (%) | 100 | **** | **** | **** | **** | **** |
| Mean DX | 39 | **** | **** | **** | **** | **** |
| Mean DY | -50 | **** | **** | **** | **** | **** |
| Mean AT | -57 | **** | **** | **** | **** | **** |
| Mean CT | 29 | **** | **** | **** | **** | **** |
| Mean DPE | 64 | **** | **** | **** | **** | **** |
| 2007 DPE * | 52 | 111 | 191 | 248 | 453 | 399 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of the storm's observed track and forecasts
Alma only briefly reached tropical storm status and no forecasts were verified.
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
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 36 | 26 | 20 | 14 | 8 | 4 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 9 | -24 | -113 | -144 | -258 | -612 |
| Mean DY | 0 | -7 | -103 | -157 | -253 | -484 |
| Mean AT | 0 | -32 | -121 | -192 | -339 | -770 |
| Mean CT | -1 | -19 | -24 | 4 | 84 | -56 |
| Track skill (%) | **** | 32 | 51 | 67 | **** | **** |
| Mean DPE | 65 | 114 | 235 | 328 | 462 | 862 |
| 2007 DPE * | 62 | 125 | 193 | 266 | 404 | 469 |
| Intensity skill (%) | **** | 23 | 30 | 14 | -25 | 0 |
* DPE for all northern hemisphere storms in 2007 season
Track forecast errors for this month's storms were above last season's average at all lead times except 24 hours. Overall, there was a slow bias and skill scores against CLIPER were high. The overall intensity tendency skill score was 17%.
