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Tropical cyclone activity and forecasts - April 2004

1. Tropical cyclone activity

1.1 Tropical cyclones ending during the month

NWP NEP NAT NI SWI AUS TOTAL
Total number ending during the month 1 0 0 0 0 1 2
 
Name Identifier Basin Start Date End Date 1-minute MSW 10-minute MSW
Sudal 03W NWP 03 April 16 April 130 85
- 22P AUS 07 April 09 April 35 -

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.

Click here for details of the TC verification technique and an explanation of error statistics and their sign conventions.

2.1 Individual Tropical Cyclone Summaries

Name: SUDAL Identifier: 03W
Basin: NORTH-WEST PACIFIC
Start date: 04.04.2004 End date: 16.04.2004
1-minute MSW: 130 knots 10-minute MSW: 85 knots

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 25 23 21 19 17 15
Detection Rate (%) 100 100 100 100 100 100
Mean DX -15 7 62 166 206 330
Mean DY 7 98 123 105 44 11
Mean AT -1 57 106 108 -34 -65
Mean CT -17 37 80 119 194 291
Track skill (%) **** 7 25 41 **** ****
Mean DPE 48 137 214 295 293 416
2003 DPE * 54 150 251 359 498 643
Intensity skill (%) **** 48 14 68 41 47


* DPE for all storms in the 2003 season in the NWP basin

A plot of the storm's observed track and forecasts.

Sudal was the first significant tropical cyclone of the northern hemisphere season. Whilst the model had a right-of-track bias, track forecast errors were below last season's average at all lead times. Skill scores were also positive, particularly at longer lead times.

 

Name: - Identifier: 22P
Basin: AUSTRALIAN (South Pacific)
Start date: 07.04.2004 End date: 09.04.2004
1-minute MSW: 35 knots 10-minute MSW: -

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 TC's observed track.

 

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:- 2
Number of storms used in statistics below:- 1

Table of Mean Error Statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly Verified 25 23 21 19 17 15
Detection Rate (%) 100 100 100 100 100 100
Mean DX -15 7 62 166 206 330
Mean DY 7 98 123 105 44 11
Mean AT -1 57 016 018 -34 -65
Mean CT -17 37 80 119 194 291
Track skill (%) **** 7 25 41 **** ****
Mean DPE 48 137 214 295 293 416
2003 DPE * 55 149 249 355 491 612
Intensity skill (%) **** 48 14 68 41 47


* DPE for all Northern Hemisphere storms in 2003 season

Comments:

Since the track of only one tropical cyclone was verified this month, the overall results comprise just those for Super Typhoon Sudal. The overall intensity tendency skill score was 43%.