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 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.
2.1 Individual Tropical Cyclone Summaries
Name: RAYMOND Identifier: 07S
Basin: AUSTRALIAN (SE Indian)
Start date: 31.12.2004 End date: 03.01.2005
1-minute MSW: 50 knots 10-minute MSW: 45 knots
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* DPE for all storms in the 2003-4 season in the AUS basin
A
plot of the storm's observed track and forecasts.
Raymond only briefly reached tropical storm status and just one forecast was verified.
Name: KERRY Identifier: 08P
Basin: AUSTRALIAN (SW Pacific)
Start date: 05.01.2005 End date: 13.01.2005
1-minute MSW: 90 knots 10-minute MSW: 75 knots
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* DPE for all storms in the 2003-4 season in the AUS basin
A
plot of the storm's observed track and forecasts.
Kerry initially moved south-westwards, then entered an area of slack steering flow. At this time ECMWF ensemble tracks indicated a period of very low predictability in forecasts with possible tracks from the north-west to the south-east. The Met Office global model showed similar unpredictability for several runs. The storm eventually drifted southwards before dissipation. Consequently, long lead time forecasts had very large errors. However, skill scores over CLIPER between T+24 and T+72 were very high.
Name: SALLY Identifier: 09S
Basin: AUSTRALIAN (SE Indian)
Start date: 08.01.2005 End date: 10.01.2005
1-minute MSW: 40 knots 10-minute MSW: 45 knots
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* DPE for all storms in the 2003-4 season in the AUS basin
A
plot of the storm's observed track and forecasts.
Just two forecasts were verified for Tropical Storm Sally. Track errors were slightly above last season's average.
Name: - Identifier: 01B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 09.01.2005 End date: 10.01.2005
1-minute MSW: 25 knots 10-minute MSW: -
There are no verification statistics or forecast plot for this tropical
cyclone since its 1-minute averaged winds did not reach tropical storm
strength.
A
plot of the storm's observed track.
Name: KULAP Identifier: 01W
Basin: NORTH-WEST PACIFIC
Start date: 13.01.2005 End date: 19.01.2005
1-minute MSW: 60 knots 10-minute MSW: 50 knots
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* DPE for all storms in the 2004 season in the NWP basin
A
plot of the storm's observed track and forecasts.
Track forecast errors were above last season's average for short lead times, but below the average for longer lead times. Skill scores against CLIPER also reflected this trend.
Name: HIBARU Identifier: 02B
Basin: NORTH INDIAN (Bay of Bengal)
Start date: 14.01.2005 End date: 17.01.2005
1-minute MSW: 35 knots 10-minute MSW: 35 knots
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* DPE for all storms in the 2004 season in the NI basin
A
plot of the storm's observed track and forecasts.
Just two forecasts were verified for this storm. Track errors were low.
Name: - Identifier: 10S
Basin: AUSTRALIAN (SE Indian)
Start date: 15.01.2005 End date: 17.01.2005
1-minute MSW: 35 knots 10-minute MSW: 30 knots
There are no verification statistics or forecast plot for this tropical
cyclone since its 10-minute averaged winds did not reach tropical storm
strength.
A
plot of the storm's observed track.
Name: DAREN Identifier: 11S
Basin: SOUTH-WEST INDIAN
Start date: 17.01.2005 End date: 21.01.2005
1-minute MSW: 45 knots 10-minute MSW: 40 knots
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* DPE for all storms in the 2003-4 season in the SWI basin
A
plot of the storm's observed track and forecasts.
Daren only briefly reached tropical storm status and only one forecast was verified.
Name: ERNEST Identifier: 12S
Basin: SOUTH-WEST INDIAN
Start date: 20.01.2005 End date: 24.01.2005
1-minute MSW: 100 knots 10-minute MSW: 90 knots
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* DPE for all storms in the 2003-4 season in the SWI basin
A
plot of the storm's observed track and forecasts.
Ernest was generally well forecast by the model with track errors below last season's average (except at T+96) and high skill scores. There was a slow bias at longer lead times.
Name: TIM Identifier: 13S
Basin: AUSTRALIAN (SE Indian)
Start date: 23.01.2005 End date: 25.01.2005
1-minute MSW: 40 knots 10-minute MSW: 45 knots
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* DPE for all storms in the 2003-4 season in the AUS basin
A
plot of the storm's observed track and forecasts.
Just two forecasts were verified for this tropical storm. Track errors were near to last season's average.
Name: FELAPI Identifier: -
Basin: SOUTH-WEST INDIAN
Start date: 27.01.2005 End date: 28.01.2005
1-minute MSW: - 10-minute MSW: 35 knots
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* DPE for all storms in the 2003-4 season in the SWI basin
A
plot of the storm's observed track and forecasts.
Daren only briefly reached tropical storm status and only 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:- 11
Number of storms used in statistics below:- 9
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* DPE for all Southern Hemisphere storms in 2003-4 season
Comments:
Although there was a high number of tropical cyclones for January, the majority were fairly short-lived. Forecast errors at shorter lead times were near to or slightly above last season's average. Skill scores against CLIPER were fairly high. Errors at longer lead times were dominated by the figures for TC Kerry which were very high. There was a slow bias, particularly at longer lead times and a tendency not to recurve soon enough (right-of-track bias in the southern hemisphere. The overall intensity tendency skill score was 13%.
