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
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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 which 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 39 levels. This is equivalent to a horizontal resolution of 93km x 62km at the equator.
2.1 Individual Tropical Cyclone Summaries
Name: MANOU Identifier: 28S
Basin: SOUTH-WEST INDIAN
Start date: 03.05.2003 End date: 10.05.2003
1-minute MSW: 65 knots 10-minute MSW: 80 knots
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A plot of the storm's observed track and forecasts.
Forecast errors were low up to T+72, but high thereafter. A few early forecasts had a right of track bias and took the storm across Madagascar, which explains the large longer range forecast errors. Other forecasts correctly predicted the stalling of the storm near to the coast of Madagascar.
Name: - Identifier: 01B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 10.05.2003 End date: 19.05.2003
1-minute MSW: 65 knots 10-minute MSW: -
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A plot of the storm's observed track and forecasts.
01B exhibited a very erratic track which forecasts did not predict particularly successfully. At the time that the storm stalled in mid Bay of Bengal forecasts had predicted continued movement north-eastwards towards the coast. The storm did eventually accelerate towards the coast and forecast errors were not far from last season's average.
Name: - Identifier: 03W
Basin: NORTH-WEST PACIFIC
Start date: 17.05.2003 End date: 20.05.2003
1-minute MSW: 35 knots 10-minute MSW: -
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* DPE for all storms in the 2002 season in the NWP basin
A plot of the storm's observed track and forecasts.
03W only briefly reached tropical storm strength and no forecasts were verified.
Name: CHAN-HOM Identifier: 04W
Basin: NORTH-WEST PACIFIC
Start date: 19.05.2003 End date: 27.05.2003
1-minute MSW: 115 knots 10-minute MSW: 85 knots
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* DPE for all storms in the 2002 season in the NWP basin
A plot of the storm's observed track and forecasts.
Forecasts for Chan-hom had a slight left-of-track bias and also failed to predict the acceleration of the storm later in its life. This resulted in very large track forecast errors at T+72 and beyond. However, the model showed skill over CLIPER up to T+72.
Name: ANDRES Identifier: 01E
Basin: NORTH-EAST PACIFIC
Start date: 20.05.2003 End date: 26.05.2003
1-minute MSW: 40 knots 10-minute MSW: -
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* DPE for all storms in the 2002 season in the NEP basin
A plot of the storm's observed track and forecasts.
Andres was a typical straight-running north-east Pacific storm. Forecasts were slow and had a right-of-track bias, which resulted in track errors above last season's average.
Name: LINFA Identifier: 05W
Basin: NORTH-WEST PACIFIC
Start date: 25.05.2003 End date: 31.05.2003
1-minute MSW: 60 knots 10-minute MSW: 55 knots
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* DPE for all storms in the 2002 season in the NWP basin
A plot of the storm's observed track and forecasts.
Like Typhoon Chan-hom earlier in the month, Linfa accelerated north-eastwards later in its life and the model forecasts did not predict this well. Hence, there was a huge slow bias and forecast errors were very high beyond T+48. However, track forecasts did show skill against CLIPER.
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:- 6
Number of storms used in statistics below:- 6
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* DPE for all Northern Hemisphere storms in 2002 season
A plot of the observed tracks of this month's storms in the North-West
Pacific basin.
A plot of the observed tracks of this month's storms in the North-East
Pacific basin.
A plot of the observed tracks of this month's storms in the North
Indian basin.
A plot of the observed tracks of this month's storms in the South-West
Indian basin.
Forecasts this month had a marked slow bias and negative cross-track bias (left-of-track in the northern hemisphere). Hence, track forecast errors were above last season's average. The model showed some skill over CLIPER. The overall intensity tendency skill score was 29%.