1. Tropical cyclone activity
1.1 Tropical cyclones ending during the month
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* Incomplete set of advisories for 10-minute winds
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 0.5625°x 0.375°x 50 levels. This is equivalent to a horizontal resolution of 62km x 42km at the equator.
Verification technique and an explanation of error statistics and their sign conventions
2.1 Individual Tropical Cyclone Summaries
Name: HUBERT Identifier: 21S
Basin: AUSTRALIAN (SE Indian)
Start date: 05.04.2006 End date: 07.04.2006
1-minute MSW: 55 knots 10-minute MSW: 55 knots
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* DPE for all storms in the 2004-5 season in the AUS basin
A plot of the storm's observed track and forecasts.
Forecasts for this storm had a right-of-track bias. Errors were near to last season's average. Skill against CLIPER at T+24 was high.
Name: ELIA Identifier: 22S
Basin: SOUTH-WEST INDIAN
Start date: 12.04.2006 End date: 16.04.2006
1-minute MSW: 45 knots 10-minute MSW: 45 knots
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* DPE for all storms in the 2004-5 season in the SWI basin
A plot of the storm's observed track and forecasts.
Errors were below last season's average and skill scores high.
Name: MONICA Identifier: 23P
Basin: AUSTRALIAN (Coral Sea/Arafura Sea)
Start date: 17.04.2006 End date: 25.04.2006
1-minute MSW: 155 knots 10-minute MSW: 135 knots
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* DPE for all storms in the 2004-5 season in the AUS basin
A plot of the storm's observed track and forecasts.
Track forecast errors were below last season's average for this cyclone and skill scores were very high. From just prior to first landfall, the model gave a good indication of the cyclone's north-westward turn once it emerged over the Gulf of Carpentaria. There was a slight right-of-track bias thereafter as the cyclone eventually made its second landfall over the Top End of Australia.
Name: MALA Identifier: 02B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 24.04.2006 End date: 29.04.2006
1-minute MSW: 115 knots 10-minute MSW: 65 knots
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* DPE for all storms in the 2005 season in the NI basin
A plot of the storm's observed track and forecasts.
Early forecasts for Cyclone Mala were poor as they predicted a slow cyclonic loop in the track. The cyclone eventually turned north-eastwards and made landfall over Myanmar. Poor initialisation due to lack of advisory data resulted in some forecast inaccuracies, with landfall predicted too far south at lead times of 48-72 hours. However, forecasts from 24 hours before landfall were good. Whilst track forecast errors were above last season's average skill scores against CLIPER were still high.
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: 4
Number of storms used in statistics below: 4
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* DPE for all Southern Hemisphere storms in 2004-5 season
Comments:
Track forecast errors were near to or below last season's averages.
Skill scores against CLIPER were high. At longer lead times there was
a slow bias and a left (right)-of-track bias in the northern (southern)
hemisphere. The overall intensity tendency skill score was -11%.