Tropical cyclone activity
| Tropical cyclones ending during the month | |||||||
|---|---|---|---|---|---|---|---|
| NWP | NEP | NAT | NI | SWI | AUS | Total | |
| Total number ending during the month | 2 | 0 | 1 | 0 | 0 | 0 | 3 |
| Tropical cyclones active during the month | ||||||
|---|---|---|---|---|---|---|
| Name | Identifier | Basin | Start date | End date | 1-minute MSW | 10-minute MSW |
| Nakri | 06W | NWP | 27 May | 03 June | 125 | 105 |
| Arthur | 01L | NAT | 31 May | 02 June | 35 | - |
| Fengshen | 07W | NWP | 18 June | 26 June | 95 | 90 |
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 |
| Boris | 02E | NEP | 27 June |
| Cristina | 03E | NEP | 27 June |
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: NAKRI Identifier: 06W
Basin: NORTH WEST PACIFIC
Start date: 27.05.2008 End date: 03.06.2008
1-minute MSW: 125 knots 10-minute MSW: 105 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 | 20 | -10 | 2 | 88 | 417 | 1293 |
| Mean DY | -8 | 2 | 76 | 194 | 401 | 459 |
| Mean AT | -3 | -19 | 17 | 150 | 468 | 1054 |
| Mean CT | 13 | 9 | 25 | 88 | 325 | 904 |
| Track skill (%) | **** | 33 | 39 | 22 | **** | **** |
| Mean DPE | 42 | 85 | 160 | 297 | 627 | 1398 |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 |
| Intensity skill (%) | **** | 50 | 40 | 25 | 67 | 0 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of the Nakri's observed track and forecasts
The first few forecasts for this typhoon predicted recurvature too early, which resulted in huge errors at longer lead times. However, later forecasts were much better. This resulted in track errors near to or below last season’s average at lead times of 72 hours or shorter. The model showed skill over CLIPER.
Name: ARTHUR Identifier:
01L
Basin: NORTH ATLANTIC
Start date: 31.05.2008 End date: 02.06.2008
1-minute MSW: 35 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 | -11 | **** | **** | **** | **** | **** |
| Mean DY | -89 | **** | **** | **** | **** | **** |
| Mean AT | 29 | **** | **** | **** | **** | **** |
| Mean CT | -39 | **** | **** | **** | **** | **** |
| Mean DPE | 123 | **** | **** | **** | **** | **** |
| 2007 DPE * | 63 | 102 | 151 | 179 | 228 | 265 |
* DPE for all storms in the 2007 season in the NAT basin
A plot of the Arthur's observed track and forecasts
Arthur was a short-lived storm and no forecasts were verified.
Name: FENGSHEN Identifier: 07W
Basin: NORTH-WEST PACIFIC
Start date: 18.06.2008 End date: 26.06.2008
1-minute MSW: 95 knots 10-minute MSW: 90 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 | 13 | 64 | 109 | 260 | 476 | 693 |
| Mean DY | -21 | -14 | -1 | 13 | 46 | 31 |
| Mean AT | -19 | -65 | -96 | -151 | -273 | -238 |
| Mean CT | -1 | 19 | 40 | 214 | 370 | 648 |
| Track skill (%) | **** | 16 | 22 | 24 | **** | **** |
| Mean DPE | 59 | 129 | 197 | 281 | 495 | 695 |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 |
| Intensity skill (%) | **** | 50 | 60 | 75 | 33 | 0 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of the Fengshen's observed track and forecasts
Some early forecasts incorrectly predicted that Fengshen would turn northwards before reaching the Philippines. However, having crossed the eastern side of the islands the forecasts were much better. Most predicted landfall near to or just to the east of Hong Kong. Only long lead time track forecast errors were above last season's average. Skill scores were positive.
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
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 30 | 24 | 20 | 16 | 12 | 8 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 15 | 27 | 55 | 174 | 447 | 993 |
| Mean DY | -8 | -6 | 37 | 91 | 223 | 245 |
| Mean AT | -10 | -42 | -40 | -1 | 98 | 408 |
| Mean CT | 4 | 14 | 32 | 151 | 347 | 776 |
| Track skill (%) | **** | 23 | 32 | 23 | **** | **** |
| Mean DPE | 55 | 107 | 178 | 289 | 561 | 1047 |
| 2007 DPE * | 66 | 127 | 193 | 262 | 401 | 472 |
| Intensity skill (%) | **** | 50 | 50 | 50 | 50 | 0 |
* DPE for all northern hemisphere storms in 2007 season
This month's figures are dominated by the two North-West Pacific typhoons Nakri and Fengshen. Forecasts exhibited similar characteristics for each - initially predicting recurvature too soon, but improving in later runs. Hence, cross-track errors at longer lead times were large. Track errors at shorter lead times were close to or below average. Track skill scores were positive. The overall intensity tendency skill score was 45%.
Tropical cyclone activity in the southern hemisphere during 2007-8 season
| Tropical cyclone activity | |||
|---|---|---|---|
| SWI | AUS | TOTAL | |
| Tropical Depressions | 0(3) | 5(2) | 5(2) |
| Tropical Storms | 7(3) | 6(8) | 13(11) |
| Hurricanes/Typhoons | 5(7) | 6(5) | 11(12) |
| Total | 12(10) | 17(15) | 29(25) |
( ) The number in brackets indicates the figure for the 2006-7 season. Definitions based on RSMC 10-minute average wind speeds are used.
Summary of all Southern Hemisphere Storms in 2007-8
Mean error statistics for all Southern Hemisphere storms that occurred in the 2007-8 season are shown below. Only storms that reached tropical storm intensity at the time of a forecast are used in the statistics below.
Total number of tropical cyclones which occurred:- 29
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 201 | 154 | 118 | 87 | 60 | 41 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | 100 | 90 |
| Mean DX |
-2 | -34 | -106 | -164 | -268 | -316 |
| Mean DY |
4 | 22 | -12 | -58 | -107 | -45 |
| Mean AT |
-4 | -26 | -22 | -28 | -64 | -149 |
| Mean CT |
6 | 6 | -13 | -54 | -60 | -17 |
| Skill (%) | **** | 33 | 33 | 27 | **** | **** |
| * 2005-6 Skill (%) | **** | 23 | 16 | 13 | **** | **** |
| Mean DPE | 54 | 122 | 240 | 385 | 549 | 714 |
| * 2005-6 DPE | 62 | 138 | 302 | 498 | 732 | 873 |
| Intensity skill (%) | **** | 38 | 41 | 26 | 13 | 3 |
* Real time figures for all Southern Hemisphere storms in 2006-7.
Southern Hemisphere warning centres recorded slightly higher activity this season than in 2006-7 in terms of verifiable forecasts. However, the numbers of storms and those attaining hurricane strength were similar.
Observed tracks of this season’s TCs.
South-west India (SWI) Western
AUS Eastern
AUS
The charts below show forecast positional errors for the last few seasons. Errors were lower than the high values of last season in both basins at all lead times. At shorter lead times, errors were back to levels seen in the few seasons prior to last season.
Skill against CLIPER was higher than last season, but still did not recover to the levels seen in the two seasons prior to that. Cross track errors recovered to fairly small negative values - a slight right-of-track bias. Along track errors showed generally small negative values (slow bias).
After last season's poor verification figures, this season saw a recovery to figures closer to those seen in the previous few seasons.
Intensity tendency skill score averaged for all forecasts was 30% in the 2007-8 Southern Hemisphere season. This compares to 18% and 31% for the previous two seasons.
A revised Southern Hemisphere summary will be issued once best track data has been collected later in the year.
Forecast Positional Errors:
SWI AUS Combined
southern hemisphere
Southern hemisphere skill
Southern hemisphere cross track errors
Southern hemisphere along track errors
