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: ZETA Identifier: 30L
Basin: NORTH ATLANTIC
Start date: 30.12.2005 End date: 06.01.2006
1-minute MSW: 55 knots 10-minute MSW: -
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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.
Zeta finally brought to an end a very long 2005 Atlantic hurricane season. Forecasts were not straight forward as the model predictions persisted in moving the storm north-westward or northward. The storm itself persisted in moving south-westward or westward. This resulted in some very large track forecast errors and low skill scores.
Name: CLARE Identifier: 05S
Basin: AUSTRALIAN (SE Indian)
Start date: 07.01.2006 End date: 10.01.2006
1-minute MSW: 60 knots 10-minute MSW: 75 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 Clare were very good, with landfall well predicted. Track forecast errors were low and skill scores high.
Name: TAM Identifier: 06P
Basin: AUSTRALIAN (S Pacific)
Start date: 08.01.2006 End date: 14.01.2006
1-minute MSW: 35 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.
Tam was relatively short-lived as the storm accelerated south-eastwards soon after formation. Track forecasts tended to be too slow.
Name: - Identifier: 01A
Basin: NORTH INDIAN (Arabian Sea)
Start date: 13.01.2006 End date: 14.01.2006
1-minute MSW: 35 knots 10-minute MSW: 30 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.
Just one forecast was verified for this short-lived storm. The track error in this forecast was large.
Name: URMIL Identifier: 07P
Basin: AUSTRALIAN (S Pacific)
Start date: 14.01.2006 End date: 15.01.2006
1-minute MSW: 60 knots 10-minute MSW: 60 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.
Just one forecast was verified for this short-lived storm. The track error for this forecast was small.
Name: DARYL Identifier: 08S
Basin: AUSTRALIAN (SE Indian)
Start date: 18.01.2006 End date: 23.01.2006
1-minute MSW: 65 knots 10-minute MSW: 65 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 above last season's average at T+24 and T+48, but below average at longer lead times. The model tended to steer the storm leftward towards the coast too much. Skill scores against CLIPER were generally good.
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:
The two longest lasting storms to end this month had the largest track
forecast errors, so the overall figures for the month reflect this.
Skill scores against CLIPER were still positive at all times. There
was a polewards bias in forecasts. The overall intensity tendency skill
score was 27%.
