Tropical cyclone activity and forecasts - September 2008
Tropical cyclone activity
| NWP | NEP | NAT | NI | SWI | AUS | TOTAL | |
|---|---|---|---|---|---|---|---|
| Total number ending during the month | 6 | 2 | 5 | 1 | 0 | 0 | 14 |
| Name | Identifier | Basin | Start date | End date | 1-minute MSW | 10-minute MSW |
|---|---|---|---|---|---|---|
| Gustav | 07L | NAT | 25 August | 02 September | 130 | - |
| Hanna | 08L | NAT | 28 August | 07 September | 70 | - |
| Ike | 09L | NAT | 01 September | 14 September | 125 | - |
| Josephine | 10L | NAT | 02 September | 06 September | 55 | - |
| Karina | 12E | NEP | 02 September | 03 September | 35 | - |
| Lowell | 13E | NEP | 07 September | 12 September | 50 | - |
| Sinlaku | 15W | MWP | 08 September | 20 September | 125 | 90 |
| - | 16W | NWP | 10 September | 11 September | 35 | 30 |
| - | 17W | NWP | 14 September | 14 september | 30 | 30 |
| - | 02B | NI | 16 September | 16 September | 35 | 30 |
| Hagupit | 18W | NWP | 18 September | 24 September | 120 | 90 |
| Jangmi | 19W | NWP | 23 September | 30 September | 145 | 115 |
| Kyle | 11L | NAT | 25 September | 29 September | 65 | - |
| Mekkhala | 20W | NWP | 28 September | 30 september | 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.
Tropical cyclones still active at the end of the month
| Name | Identifier | Basin | Start date |
|---|---|---|---|
| Higos | 21W | NWP | 29 September |
| Laura | 12L | NAT | 29 september |
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: GUSTAV Identifier: 07L
Basin: NORTH ATLANTIC
Start date: 25.08.2008 End date: 02.09.2008
1-minute MSW: 130 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 15 | 13 | 11 | 9 | 7 | 5 | 3 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 21 | 16 | 19 | -11 | -58 | -178 | -338 |
| Mean DY | 12 | -22 | -47 | -111 | -162 | -234 | -426 |
| Mean AT | -17 | -30 | -66 | -73 | -68 | -55 | -61 |
| Mean CT | 14 | 5 | -5 | -57 | -143 | -299 | -536 |
| Track skill (%) | **** | 56 | 67 | 67 | **** | **** | **** |
| Mean DPE | 47 | 76 | 148 | 214 | 327 | 410 | 600 |
| 2007 DPE * | 63 | 102 | 151 | 179 | 228 | 265 | **** |
| Intensity skill (%) | **** | 54 | -9 | 33 | -14 | -20 | 33 |
* DPE for all storms in the 2007 season in the NAT basin
A plot of Gustav's observed track and forecasts
Track errors were above last season’s average at lead times of T+72 and longer. However, skill scores were very high. The model predicted the south-westward turn towards Jamaica very well. However, later forecasts predicted too strong a ridge over the southern USA resulting in a track for Gustav which was too slow and too far to the west.
Name: HANNA Identifier: 08L
Basin: NORTH ATLANTIC
Start date: 28.08.2008 End date: 07.09.2008
1-minute MSW: 70 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 20 | 18 | 6 | 14 | 12 | 10 | 8 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 3 | -21 | -105 | -151 | -243 | -413 | -523 |
| Mean DY | 30 | 69 | 104 | 119 | 65 | -99 | -347 |
| Mean AT | 3 | -35 | -35 | -35 | -149 | -314 | -285 |
| Mean CT | 2 | 62 | 55 | 22 | -64 | -256 | -475 |
| Track skill (%) | **** | 57 | 62 | 69 | **** | **** | **** |
| Mean DPE | 63 | 139 | 253 | 270 | 377 | 580 | 747 |
| 2007 DPE * | 63 | 102 | 151 | 179 | 228 | 265 | **** |
| Intensity skill (%) | **** | 33 | 38 | 29 | 17 | 40 | 50 |
* DPE for all storms in the 2007 season in the NAT basin
A plot of Hanna's observed track and forecasts
Track errors were above last season’s low values, but not significantly so. A southward component in the early part of the track was forecast, but not to the extent that occurred. The acceleration to the north-west and north was fairly well handled. Skill scores against CLIPER were high.
Name: IKE Identifier: 09L
Basin: NORTH ATLANTIC
Start date: 01.09.2008 End date: 14.09.2008
1-minute MSW: 125 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 25 | 23 | 21 | 19 | 17 | 15 | 13 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 93 | 85 |
| Mean DX | 14 | 5 | 12 | 29 | 105 | 171 | 272 |
| Mean DY | 4 | 24 | 66 | 97 | 141 | 83 | 36 |
| Mean AT | -11 | -15 | -41 | -86 | -141 | -219 | -269 |
| Mean CT | 7 | 17 | 48 | 73 | 110 | 136 | 217 |
| Track skill (%) | **** | 43 | 48 | 62 | **** | **** | **** |
| Mean DPE | 39 | 71 | 160 | 222 | 306 | 395 | 512 |
| 2007 DPE * | 63 | 102 | 151 | 179 | 228 | 265 | **** |
| Intensity skill (%) | **** | 22 | 52 | 37 | 29 | 43 | -27 |
* DPE for all storms in the 2007 season in the NAT basin
A plot of Ike's observed track and forecasts
In common with other models a northwards turn near the Bahamas or Florida was initially predicted. However, once the south-westwards movement commenced, track forecasts were very good right through to landfall. Hence, track errors were low and skill scores high. There was a slight slow bias.
Name: JOSEPHINE Identifier: 10L
Basin: NORTH ATLANTIC
Start date: 02.09.2008 End date: 06.09.2008
1-minute MSW: 55 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 7 | 5 | 3 | 1 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | 100 | 100 | **** | **** | **** |
| Mean DX | -11 | -60 | -279 | -684 | **** | **** | **** |
| Mean DY | -34 | -20 | 4 | 122 | **** | **** | **** |
| Mean AT | -4 | 46 | 252 | 659 | **** | **** | **** |
| Mean CT | -21 | -23 | -97 | -233 | **** | **** | **** |
| Track skill (%) | **** | 17 | 45 | **** | **** | **** | **** |
| Mean DPE | 52 | 124 | 319 | 699 | **** | **** | **** |
| 2007 DPE * | 63 | 102 | 151 | 179 | 228 | 265 | **** |
| Intensity skill (%) | **** | 100 | 100 | 100 | **** | **** | **** |
* DPE for all storms in the 2007 season in the NAT basin
A plot of Josephine's observed track and forecasts
Forecasts for Josephine were generally too fast, although the model showed skill over CLIPER.
Name: KARINA Identifier: 12E
Basin: NORTH-EAST PACIFIC
Start date: 02.09.2008 End date: 03.09.2008
1-minute MSW: 35 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 2 | 0 | 0 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | **** | **** | **** | **** | **** | **** |
| Mean DX | -5 | **** | **** | **** | **** | **** | **** |
| Mean DY | -22 | **** | **** | **** | **** | **** | **** |
| Mean AT | -13 | **** | **** | **** | **** | **** | **** |
| Mean CT | -51 | **** | **** | **** | **** | **** | **** |
| Mean DPE | 33 | **** | **** | **** | **** | **** | **** |
| 2007 DPE * | 56 | 112 | 192 | 246 | 453 | 397 | **** |
* DPE for all storms in the 2007 season in the NEP basin
A plot of Karina's observed track and forecasts
Karina was only briefly a tropical storm and no 24-hour forecasts were verified.
Name: LOWELL Identifier: 13E
Basin: NORTH-EAST PACIFIC
Start date: 07.09.2008 End date: 12.09.2008
1-minute MSW: 50 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 6 | 4 | 2 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | 100 | **** | **** | **** | **** |
| Mean DX | -28 | -157 | -296 | **** | **** | **** | **** |
| Mean DY | -54 | 6 | 62 | **** | **** | **** | **** |
| Mean AT | -19 | 97 | 220 | **** | **** | **** | **** |
| Mean CT | -50 | -73 | -143 | **** | **** | **** | **** |
| Track skill (%) | **** | -62 | -91 | **** | **** | **** | **** |
| Mean DPE | 76 | 167 | 299 | **** | **** | **** | **** |
| 2007 DPE * | 56 | 112 | 192 | 246 | 453 | 397 | **** |
| Intensity skill (%) | **** | 50 | 100 | **** | **** | **** | **** |
* DPE for all storms in the 2007 season in the NEP basin
A plot of Lowell's observed track and forecasts
Forecasts for Lowell were too fast and did not predict the eastward turn well.
Name: SINLAKU Identifier: 15W
Basin: NORTH-WEST PACIFIC
Start date: 08.09.2008 End date: 20.09.2008
1-minute MSW: 125 knots 10-minute MSW: 90 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 24 | 22 | 20 | 18 | 16 | 14 | 12 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 8 | -13 | -84 | -120 | -145 | -178 | -65 |
| Mean DY | 19 | -34 | -78 | -58 | -36 | -8 | 141 |
| Mean AT | 13 | -43 | -130 | -182 | -175 | -220 | -22 |
| Mean CT | 1 | 15 | 9 | -50 | -22 | -68 | -133 |
| Track skill (%) | **** | 43 | 47 | 59 | **** | **** | **** |
| Mean DPE | 45 | 90 | 165 | 220 | 239 | 278 | 268 |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 | **** |
| Intensity skill (%) | **** | 27 | 10 | 22 | 50 | -29 | 33 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of Sinlaku's observed track and forecasts
Track forecast errors were low for this typhoon. The slow movement near Taiwan and the sharp recurvature were well predicted, although there was a slow bias in forecasts. Skill scores against CLIPER were high.
Name: - Identifier: 16W
Basin: NORTH-WEST PACIFIC
Start date: 10.09.2008 End date: 11.09.2008
1-minute MSW: 35 knots 10-minute MSW: 30 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 3 | 1 | 0 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | **** | **** | **** | **** | **** |
| Mean DX | 31 | -84 | **** | **** | **** | **** | **** |
| Mean DY | 45 | 111 | **** | **** | **** | **** | **** |
| Mean AT | 16 | 127 | **** | **** | **** | **** | **** |
| Mean CT | 38 | 47 | **** | **** | **** | **** | **** |
| Mean DPE | 72 | 136 | **** | **** | **** | **** | **** |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 | **** |
| Intensity skill (%) | **** | 100 | **** | **** | **** | **** | **** |
* DPE for all storms in the 2007 season in the NWP basin
A plot of 16W's observed track and forecasts
16W was briefly a tropical storm (according to JTWC) and just one forecast was verified.
Name: - Identifier: 17W
Basin:NORTH-WEST PACIFIC
Start date: 14.09.2008 End date: 14.09.2008
1-minute MSW: 30 knots 10-minute MSW: 35 knots
A plot of 17W's observed track and forecasts
There are no verification statistics or forecast plot for this tropical cyclone since its 1-minute averaged winds did not reach tropical storm strength.
Name: - Identifier: 02B
Basin:NORTH INDIAN (Bay of Bengal)
Start date: 16.09.2008 End date: 16.09.2008
1-minute MSW: 35 knots 10-minute MSW: 30 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | **** | **** | **** | **** | **** | **** |
| Mean DX | -62 | **** | **** | **** | **** | **** | **** |
| Mean DY | -44 | **** | **** | **** | **** | **** | **** |
| Mean DPE | 80 | **** | **** | **** | **** | **** | **** |
| 2007 DPE * | 77 | 147 | 203 | 319 | 509 | 387 | **** |
* DPE for all storms in the 2007 season in the NI basin
A plot of 02B's observed track and forecasts
02B briefly attained tropical storm status (according to JTWC). No forecasts were verified.
Name: HAGUPIT Identifier: 18W
Basin: NORTH-WEST PACIFIC
Start date: 18.09.2008 End date: 24.09.2008
1-minute MSW: 120 knots 10-minute MSW: 90 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 11 | 9 | 7 | 5 | 3 | 1 | 0 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 100 | **** |
| Mean DX | 9 | 0 | 12 | 98 | 173 | 197 | **** |
| Mean DY | -34 | -26 | -62 | -133 | -160 | -133 | **** |
| Mean AT | -14 | -14 | -37 | -121 | -194 | -212 | **** |
| Mean CT | -28 | -15 | -50 | -110 | -118 | -100 | **** |
| Track skill (%) | **** | 49 | 79 | 78 | **** | **** | ***** |
| Mean DPE | 62 | 95 | 122 | 198 | 260 | 235 | **** |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 | **** |
| Intensity skill (%) | **** | 78 | 43 | 100 | 33 | 100 | **** |
* DPE for all storms in the 2007 season in the NWP basin
A plot of Hagupit's observed track and forecasts
Track errors were low for this storm and skill scores high. There was a slight slow and left-of-track bias.
Name: JANGMI Identifier: 19W
Basin: NORTH-WEST PACIFIC
Start date: 23.09.2008 End date: 30.09.2008
1-minute MSW: 145 knots 10-minute MSW: 115 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 14 | 12 | 10 | 8 | 6 | 4 | 2 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 6 | -30 | -51 | -205 | -430 | -600 | -648 |
| Mean DY | 20 | -10 | -101 | -303 | -432 | -582 | -706 |
| Mean AT | -1 | -7 | -80 | -287 | -599 | -909 | -951 |
| Mean CT | 16 | -47 | -130 | -172 | -222 | -37 | 237 |
| Track skill (%) | **** | 27 | 45 | -22 | **** | **** | ***** |
| Mean DPE | 68 | 111 | 180 | 403 | 683 | 926 | 981 |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 | **** |
| Intensity skill (%) | **** | 33 | -20 | 0 | 67 | 50 | 0 |
* DPE for all storms in the 2007 season in the NWP basin
A plot of Jangmi's observed track and forecasts
Early forecasts had a left-of-track bias, but later forecasts predicted recurvature well. Track forecast errors were large due to the early bias.
Name: KYLE Identifier: 11L
Basin: NORTH ATLANTIC
Start date: 25.09.2008 End date: 29.09.2008
1-minute MSW: 65 knots 10-minute MSW: - knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 7 | 5 | 3 | 1 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | **** | **** |
| Mean DX | -14 | -27 | -47 | -140 | **** | **** | **** |
| Mean DY | 10 | -70 | -196 | -378 | **** | **** | **** |
| Mean AT | 3 | -79 | -209 | -407 | **** | **** | **** |
| Mean CT | -11 | -17 | -18 | -8 | **** | **** | ***** |
| Track skill (%) | **** | 61 | 78 | **** | **** | **** | ***** |
| Mean DPE | 55 | 96 | 211 | 408 | **** | **** | **** |
| 2007 DPE * | 63 | 102 | 151 | 179 | 228 | 265 | **** |
| Intensity skill (%) | **** | -20 | 33 | -100 | **** | **** | **** |
* DPE for all storms in the 2007 season in the NAT basin
A plot of Kyle's observed track and forecasts
Track forecasts for Kyle were slow, thus predicting landfall too late. Skill scores against CLIPER were high.
Name: MEKKHALA Identifier: 20W
Basin: NORTH-WEST PACIFIC
Start date: 28.09.2008 End date: 30.09.2008
1-minute MSW: 55 knots 10-minute MSW: 50 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 2 | 0 | 0 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | **** | **** | **** | **** | **** | **** |
| Mean DX | -11 | **** | **** | **** | **** | **** | **** |
| Mean DY | -18 | **** | **** | **** | **** | **** | **** |
| Mean AT | 1 | **** | **** | **** | **** | **** | **** |
| Mean CT | -19 | **** | **** | **** | **** | **** | ***** |
| Mean DPE | 42 | **** | **** | **** | **** | **** | **** |
| 2007 DPE * | 70 | 136 | 201 | 276 | 404 | 517 | **** |
* DPE for all storms in the 2007 season in the NWP basin
A plot of Mekkhala's observed track and forecasts
Mekkhala was briefly a tropical storm 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: 14
Number of storms used in statistics below: 13
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | |
|---|---|---|---|---|---|---|---|
| Possibly verified | 137 | 112 | 93 | 75 | 61 | 49 | 38 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 98 | 95 |
| Mean DX | 6 | -16 | -52 | -77 | -97 | -153 | -119 |
| Mean DY | 6 | 1 | -10 | -25 | -26 | -74 | -94 |
| Mean AT | -3 | -19 | -56 | -116 | -191 | -279 | -211 |
| Mean CT | -1 | 7 | -3 | -25 | -32 | -70 | -115 |
| Track skill (%) | **** | 46 | 57 | 60 | **** | **** | **** |
| Mean DPE | 53 | 100 | 185 | 256 | 340 | 442 | 516 |
| 2007 DPE * | 66 | 127 | 193 | 262 | 401 | 472 | **** |
| Intensity skill (%) | **** | 38 | 27 | 31 | 31 | 17 | 17 |
* Best track DPE for all Northern Hemisphere storms in 2007 season
Results for this month were very good. Track forecast errors were below last season’s average and skill scores against CLIPER were high. Biases were small. The overall intensity Track forecast errors were near to or below last season’s average. Skill scores against CLIPER were high. There was a slow bias in forecasts. The overall intensity tendency skill score was 29%.
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