Tropical cyclone activity and forecasts - May 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 | 1 | 1 | 1 | 0 | 1 | 5 |
| Name | Identifier | Basin | Start date | End date | 1-minute MSW | 10-minute MSW |
|---|---|---|---|---|---|---|
| Andrea | 01L | NAT | 09 May | 13 May | 45 | - |
| Akash | 01B | NI | 13 May | 15 May | 65 | 55 |
| Yutu | 02W | NWP | 16 May | 22 May | 125 | 95 |
| Pierre | 24P | AUS | 17 May | 18 May | 40 | 40 |
| Alvin | 01E | NEP | 27 May | 31 May | 35 | - |
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
| Name | Identifier | Basin | Start Date |
|---|---|---|---|
| Barbara | 02E | NEP | 29 May |
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: ANDREA Identifier: 01L
Basin: NORTH ATLANTIC
Start date: 09.05.2007 End
date: 13.05.2007
1-minute MSW: 45 knots
10-minute MSW: -
| 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 | 53 | **** | **** | **** | **** | **** |
| Mean DY | -28 | **** | **** | **** | **** | **** |
| Mean AT | -48 | **** | **** | **** | **** | **** |
| Mean CT | 0 | **** | **** | **** | **** | **** |
| Mean DPE | 63 | **** | **** | **** | **** | **** |
| 2006 DPE * | 46 | 109 | 213 | 322 | 425 | 529 |
* DPE for all storms in the 2006 season in the NAT basin
 |
Plot of the storm's observed track and forecasts |
Andrea was a subtropical storm, which only reached this status for a short while. Hence, no forecasts were verified.
Name: AKASH Identifier: 01B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 13.05.2007 End date: 15.05.2007
1-minute MSW: 65 knots 10-minute MSW: 55
knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
|---|---|---|---|---|---|---|
| Possibly verified | 3 | 1 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | **** | **** | **** | **** |
| Mean DX | -11 | -52 | **** | **** | **** | **** |
| Mean DY | -26 | -222 | **** | **** | **** | **** |
| Mean AT | 26 | -227 | **** | **** | **** | **** |
| Mean CT | -2 | -9 | **** | **** | **** | **** |
| Mean DPE | 66 | 228 | **** | **** | **** | **** |
| 2006 DPE * | 93 | 164 | 254 | 443 | 940 | 897 |
| Intensity skill (%) | **** | 100 | **** | **** | **** | **** |
* DPE for all storms in the 2006 season in the NI basin
 |
Plot of the storm's observed track and forecasts |
Akash was short-lived and just one forecast was verified.
Name: YUTU Identifier: 02W
Basin: NORTH-WEST PACIFIC
Start date: 16.05.2007 End date: 22.05.2007
1-minute MSW: 125 knots 10-minute MSW: 95 knots
| 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 | 10 | -6 | 15 | -95 | -687 | -1605 |
| Mean DY | 18 | 19 | 17 | -53 | -396 | -890 |
| Mean AT | 8 | -5 | 21 | -111 | -792 | -1830 |
| Mean CT | -1 | -13 | -18 | -34 | -85 | -125 |
| Track skill (%) | **** | 58 | 77 | 68 | **** | **** |
| Mean DPE | 40 | 74 | 116 | 350 | 798 | 1835 |
| 2006 DPE * | 60 | 114 | 204 | 304 | 422 | 551 |
| Intensity skill (%) | **** | 33 | -43 | 20 | -100 | 100 |
* DPE for all storms in the 2006 season in the NWP basin
 |
Plot of the storm's observed track and forecasts |
Short range forecasts were good for this typhoon and skill scores against CLIPER were high. The few verifiable longer lead time forecasts had large errors due to a slow bias around the time of recurvature.
Name: PIERRE Identifier: 24P
Basin: AUSTRALIAN (Coral Sea)
Start date: 17.05.2007 End date: 18.05.2007
1-minute MSW: 40 knots 10-minute MSW: 40 knots
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
|---|---|---|---|---|---|---|
| Possibly verified | 3 | 1 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | **** | **** | **** | **** |
| Mean DX | 53 | **** | **** | **** | **** | **** |
| Mean DY | -28 | **** | **** | **** | **** | **** |
| Mean AT | -48 | **** | **** | **** | **** | **** |
| Mean CT | 0 | **** | **** | **** | **** | **** |
| Mean DPE | 63 | **** | **** | **** | **** | **** |
| 2005-6 DPE * | 46 | 109 | 213 | 322 | 425 | 529 |
| Intensity skill (%) | **** | 100 | **** | **** | **** | **** |
* DPE for all storms in the 2005-6 season in the AUS basin
 |
Plot of the storm's observed track and forecasts |
Pierre was short-lived and just one forecast was verified.
Name: ALVIN Identifier: 01E
Basin: NORTH-EAST PACIFIC
Start date: 27.05.2007 End date: 31.05.2007
1-minute MSW: 35 knots 10-minute MSW: -
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
|---|---|---|---|---|---|---|
| Possibly verified | 3 | 1 | 0 | 0 | 0 | 0 |
| Detection rate (%) | 100 | 100 | **** | **** | **** | **** |
| Mean DX | 4 | -174 | **** | **** | **** | **** |
| Mean DY | -52 | -11 | **** | **** | **** | **** |
| Mean AT | -2 | 68 | **** | **** | **** | **** |
| Mean CT | -33 | -161 | **** | **** | **** | **** |
| Track skill (%) | **** | -150 | **** | **** | **** | **** |
| Mean DPE | 54 | 175 | **** | **** | **** | **** |
| 2006 DPE * | 51 | 103 | 185 | 265 | 366 | 430 |
* DPE for all storms in the 2006 season in the NEP basin
 |
Plot of the storm's observed track and forecasts |
Alvin only briefly reached tropical storm status and just one forecast was 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: 5
Number of storms used in statistics below: 5
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
|---|---|---|---|---|---|---|
| Possibly verified | 22 | 12 | 7 | 5 | 3 | 1 |
| Detection rate (%) | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 12 | -23 | 15 | -95 | -687 | -1605 |
| Mean DY | -3 | -6 | 17 | -53 | -396 | -890 |
| Mean AT | 4 | -17 | 21 | -111 | -792 | -1830 |
| Mean CT | -8 | -24 | -18 | -34 | -85 | -125 |
| Track skill (%) | **** | 49 | 77 | 68 | **** | **** |
| Mean DPE | 47 | 90 | 116 | 350 | 798 | 1835 |
| 2006 DPE * | 57 | 112 | 203 | 303 | 422 | 537 |
| Intensity skill (%) | **** | 50 | -43 | 20 | -100 | 100 |
* DPE for all nouthern hemisphere storms in 2006 season
Comments:
There were five storms this month, but most were short lived. Hence,
the number of verifiable forecasts was small. Track forecast errors
were below last season’s average at short lead times, but above
average at longer lead times. There was a slow and left-of track bias
and skill scores against CLIPER were high. The overall intensity tendency
skill score was 7%.
