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
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 0.83°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: NESAT Identifier: 04W
Basin: NORTH-WEST PACIFIC
Start date: 30.05.2005 End date: 11.06.2005
1-minute MSW: 125 knots 10-minute MSW: 95 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.
Forecasts were very good for Nesat. Track errors were below last season's average and skill scores were high. The recurvature was well forecast as was the northward jolt later in the storm's lifetime.
Name: ARLENE Identifier: 01L
Basin: NORTH ATLANTIC
Start date: 08.06.2005 End date: 12.06.2005
1-minute MSW: 60 knots 10-minute MSW: -
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* DPE for all storms in the 2004 season in the NAT basin
A plot of the storm's observed track and forecasts.
Arlene was relatively short-lived, but the forecast track including location of landfall was well predicted.
Name: BEATRIZ Identifier: 02E
Basin: NORTH-EAST PACIFIC
Start date: 21.06.2005 End date: 24.06.2005
1-minute MSW: 45 knots 10-minute MSW: -
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* DPE for all storms in the 2004 season in the NEP basin
A plot of the storm's observed track and forecasts.
Just one forecast was verified for this storm. The track forecast error was small.
Name: CALVIN Identifier: 03E
Basin: NORTH-EAST PACIFIC
Start date: 26.06.2005 End date: 29.06.2005
1-minute MSW: 45 knots 10-minute MSW: -
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* DPE for all storms in the 2004 season in the NEP basin
A plot of the storm's observed track and forecasts.
Just two forecasts were verified for this storm. The forecast error was above last season's average.
Name: BRET Identifier: 02L
Basin: NORTH ATLANTIC
Start date: 28.06.2005 End date: 30.06.2005
1-minute MSW: 35 knots 10-minute MSW: -
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* DPE for all storms in the 2004 season in the NAT basin
A plot of the storm's observed track and forecasts.
No forecasts were verified for Bret which was a short-lived storm.
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:- 5
Number of storms used in statistics below:- 5
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* DPE for all Northern Hemisphere storms in 2004 season
Comments:
Typhoon Nesat made up the bulk of this month's statistics. Overall,
track forecast errors were low and skill scores high. There were no
significant biases. The overall intensity tendency skill score was 76%.
3. TROPICAL CYCLONE ACTIVITY in the SOUTHERN HEMISPHERE DURING 2004-5 SEASON
| SWI | AUS | TOTAL | |
| Tropical Depressions | 1(1) | 2(1) | 3(2) |
| Tropical Storms | 6(5) | 9(6) | 15(11) |
| Hurricanes/Typhoons | 4(4) | 8(6) | 12(11) |
| Total | 11(10) | 19(13) | 30(24) |
( ) The number in brackets indicates the figure for the 2003-4 season. Definitions based on RSMC 10-minute average wind speeds are used.
3.1 Summary of all Southern Hemisphere Storms in 2004-5
Mean error statistics for all Southern Hemisphere storms that occurred in the 2004-5 season are shown below. Only storms that reached tropical storm intensity at the time of a forecast are used in the statistics below.
Total number of tropical cyclones which occurred:- 30
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* Best track figures for all Southern Hemisphere storms in 2003-4.
Comments:
Southern Hemisphere warning centres recorded 30 tropical cyclones in
the 2004-5 season. The 2004-5 season was more active than last season,
primarily due to greater activity in the Australian region. 12 of the
30 tropical cyclones reached hurricane/typhoon strength.
SWI 
Western AUS
Eastern AUS
The charts show forecast positional errors for the last few seasons. In the South-West Indian basin, forecast errors were similar to recent seasons at lead times up to T+72, but much higher at T+96 and T+120. The latter seems to be primarily due to some very poor longer range forecasts for TC Bento. In the Australian basin forecast errors were lower than last season at all lead times except T+96. Overall, errors were low up to T+72, but high at longer lead times.
Skill scores were very high and the highest ever achieved at T+48
and T+72. Cross track errors showed a right-of-track bias in forecasts,
but smaller than previous seasons. Along track errors maintained fairly
low values at short lead times.
Intensity tendency skill score averaged for all forecasts was 30% in
the 2004-5 Southern Hemisphere season. This compares to the figure of
22% for the 2003-4 season.
A revised Southern Hemisphere summary will be issued once best track data has been collected later in the year.
Forecast positional errors
Southern Hemisphere skill.
Southern Hemisphere Cross Track errors.
Southern Hemisphere Along Track errors.
