1. Tropical cyclone activity
1.1 Tropical cyclones ending during the month
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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 0.83°x 0.55°x 38 levels. This is equivalent to a horizontal resolution of 93km x 62km at the equator.
Click here for details of the TC verification technique and an explanation of error statistics and their sign conventions.
2.1 Individual Tropical Cyclone Summaries
Name: - Identifier: 01A
Basin: NORTH INDIAN (Arabian Sea)
Start date: 05.05.2004 End date: 10.05.2004
1-minute MSW: 45 knots 10-minute MSW: - knots
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* DPE for all storms in the 2003 season in the NI basin
A plot of the storm's observed track and forecasts.
Apart from at T+24, forecasts for this storm where good with below average track errors. The low skill score against CLIPER at T+72 was due to an exceptionally low CLIPER forecast error at this time.
Name: JUBA Identifier: 23S
Basin: SOUTH-WEST INDIAN
Start date: 05.05.2004 End date: 15.05.2004
1-minute MSW: 65 knots 10-minute MSW: 55 knots
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* DPE for all storms in the 2002-3 season in the SWI basin
A plot of the storm's observed track and forecasts.
Just two forecasts were verified for this storm which had errors above last season's average.
Name: NIDA Identifier: 04W
Basin: NORTH-WEST PACIFIC
Start date: 13.05.2004 End date: 21.05.2004
1-minute MSW: 140 knots 10-minute MSW: 90 knots
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* DPE for all storms in the 2003 season in the NWP basin
A plot of the storm's observed track and forecasts.
Track errors were generally above last season's average for this typhoon. The direction of motion was very well forecast, but there was a fast bias at longer lead times resulting in the large forecast errors.
Name: - Identifier: 05W
Basin: NORTH-WEST PACIFIC
Start date: 15.05.2004 End date: 17.05.2004
1-minute MSW: 35 knots 10-minute MSW: - knots
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* DPE for all storms in the 2003 season in the NWP basin
A plot of the storm's observed track and forecasts.
05W briefly made tropical storm status and no forecasts were verified
Name: OMAIS Identifier: 06W
Basin: NORTH-WEST PACIFIC
Start date: 16.05.2004 End date: 22.05.2004
1-minute MSW: 65 knots 10-minute MSW: 50 knots
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* DPE for all storms in the 2003 season in the NWP basin
A plot of the storm's observed track and forecasts.
Track forecast errors were higher than last season's average at short lead times and lower at longer lead times. There was a slow bias in forecasts and skill was shown against CLIPER. Longer range forecasts tended to dissipate the storm too soon.
Name: - Identifier: 02B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 17.05.2004 End date: 19.05.2004
1-minute MSW: 60 knots 10-minute MSW: - knots
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* DPE for all storms in the 2003 season in the NI basin
A plot of the storm's observed track and forecasts.
T+24 forecasts had errors larger than last season, but the one T+48 forecast was virtually perfect.
Name: AGATHA Identifier: 01E
Basin: NORTH-EAST PACIFIC
Start date: 22.05.2004 End date: 25.05.2004
1-minute MSW: 45 knots 10-minute MSW: - knots
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* DPE for all storms in the 2003 season in the NEP basin
A plot of the storm's observed track and forecasts.
Just one forecast was verified for this storm which had errors above last season's average.
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:- 7
Number of storms used in statistics below:- 7
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* DPE for all Northern Hemisphere storms in 2003 season
Comments:
Track forecast errors were above last season's average at T+24, T+48 and T+120, but below at other lead times. The biases were also mixed and the model showed skill over CLIPER at T+48 and T+72. The overall intensity tendency skill was 29%.
