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 0.5625°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: BOLOETSE Identifier: 09S
Basin: SOUTH-WEST INDIAN
Start date: 25.01.2006 End date: 06.02.2006
1-minute MSW: 100 knots 10-minute MSW: 90 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.
During the storm's early stages, the model predicted the sharp westward turn towards Madagascar very well. Once the storm has reformed in the Mozambique Channel, the south-eastward movement was also well predicted, although there was a slow bias in forecasts. Track errors were below last season's average and skill scores against CLIPER high.
Name: JIM Identifier: 10P
Basin: AUSTRALIAN (SW Pacific)
Start date: 28.01.2006 End date: 01.02.2006
1-minute MSW: 80 knots 10-minute MSW: 80 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.
A plot of the storm's observed track and forecasts can be found in
Figure 2.
Although the model predicted the direction of movement well for this
storm, the forecast speed of movement was much too slow resulting in
large errors and almost no skill.
Name: VAIANU Identifier: 11P
Basin: AUSTRALIAN (SW Pacific)
Start date: 11.02.2006 End date: 16.02.2006
1-minute MSW: 75 knots 10-minute MSW: 70 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.
A plot of the storm's observed track and forecasts can be found in
Figure 3.
Vaianu was generally well predicted by the model. There was a slight
right-of-track bias in forecasts, but errors were below last season's
average.
Name: - Identifier: 12S
Basin: SOUTH-WEST INDIAN
Start date: 19.02.2006 End date: 21.02.2006
1-minute MSW: 45 knots 10-minute MSW: 40 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.
A plot of the storm's observed track and analysis can be found in
Figure 4.
12S briefly reached tropical storm status (although was not named).
No forecasts were verified.
Name: KATE Identifier: 13P
Basin: AUSTRALIAN (Coral Sea)
Start date: 22.02.2006 End date: 24.02.2006
1-minute MSW: 50 knots 10-minute MSW: 45 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.
Kate only briefly reached tropical storm status and just one forecast was verified.
Name: EMMA Identifier: 15S
Basin: AUSTRALIAN (SE Indian)
Start date: 27.02.2006 End date: 28.02.2006
1-minute MSW: 35 knots 10-minute MSW: 40 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.
Emma was only briefly a tropical storm and no forecasts were 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: 6
Number of storms used in statistics below: 6
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* DPE for all Southern Hemisphere storms in 2004-5 season
Comments:
There were three short-lived and three longer lived storms this month.
The track errors produced mixed results. Overall, errors were a little
above last season's average at T+48 and T+72, but below average at longer
lead times. Skill scores over CLIPER were modest to good. There was
a slow bias in forecasts overall. The overall intensity tendency skill
score was 9%.