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.
2.1 Individual tropical cyclone summaries
Name:CLOVIS Identifier: 06S
Basin:SOUTH-WEST INDIAN
Start date: 31.12.2006 End date: 04.01.2007
1-minute MSW: 65 knots 10-minute MSW: 60 knots
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* DPE for all storms in the 2005-06 season in the SWI basin.
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Plot of the storm's observed track and forecasts |
Forecasts for Clovis had track forecast errors below last season’s average and positive skill scores.
Name: ISOBEL Identifier: 07S
Basin:AUSTRALIAN (SE Indian)
Start date: 02.01.2007 End date: 03.01.2007
1-minute MSW: 40 knots 10-minute MSW:45 knots
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* DPE for all storms in the 2005-6 season in the AUS basin
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Plot of the storm's observed track and forecasts |
Isobel only briefly attained tropical storm status and no forecasts were verified.
Name: ZITA Identifier: 08P
Basin: AUSTRALIAN (SW Pacific)
Start date: 22.01.2007 End date: 24.01.2007
1-minute MSW: 50 knots 10-minute MSW: 60 knots
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* DPE for all storms in the 2005-6 season in the AUS basin
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Plot of the depression's observed track and forecasts |
Only a couple of forecasts were verified. The model did not predict the extent of the south-eastwards acceleration and so forecasts were slow.
Name:ARTHUR Identifier: 09P
Basin:AUSTRALIAN (SW Pacific)
Start date: 24.01.2007 End date: 27.01.2007
1-minute MSW: 65 knots 10-minute MSW: 60 knots
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* DPE for all storms in the 2005-06 season in the AUS basin
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Plot of the storm's observed track and forecasts |
Forecasts predicted the direction of motion well for this storm. However, as with Zita the rate of acceleration was not well predicted. This resulted in a slow bias and track forecast errors above last season’s average.
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 2005-06 season
Comments:
Overall, track forecast errors for this month’s storms were near to average at T+24 and T+48 and below average at T+72. The number and duration of the storms this month was fairly low (i.e. only four storms, just one of which produced a T+72 forecast). The overall intensity tendency skill score was 30%.
