Tropical cyclone activity and forecasts - September 2007

Tropical cyclone activity

Tropical cyclones ending during the month
  NWP NEP NAT NI SWI AUS TOTAL
Total number ending during the month 6 4 9 0 0 0 19
 
Tropical cyclones active during the month
Name Identifier Basin Start date End date 1-minute MSW 10-minute MSW
Fitow 10W NWP 29 August 07 September 85 65
Gil 10E NEP 29 August 02 September 40 -
Henriette 11E NEP 30 August 06 September 75 -
Felix 06L NAT 31 August 05 September 145 -
Danas 11W NWP 07 September 11 September 60 50
Gabrielle 07L NAT 08 September 11 September 45 -
Ingrid 08L NAT 12 September 17 September 40 -
Humberto 09L NAT 12 September 13 September 75 -
Nari 12W NWP 12 September 16 September 120 95
Wipha 13W NWP 15 September 19 September 135 100
Ivo 12E NEP 18 September 23 September 70 -
- 13E NEP 19 September 20 September 30 -
- 14W NWP 20 September 21 September 30 -
- 10L NAT 21 September 22 September 30 -
Francisco 15W NWP 23 September 25 September 45 45
Jerry 11L NAT 23 September 25 September 40 -
Karen 12L NAT 25 September 29 September 60* -
Lorenzo 13L NAT 25 September 28 September 65 -
Melissa 14L NAT 28 September 30 September 40 -

* Karen may be upgraded to a hurricane in post-season best track analysis

Basin name abbreviations:
NWP : North-west Pacific (west of 180° E)
NEP : North-east Pacific (east of 180° E)
NAT : North Atlantic

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.

Tropical cyclones still active at the end of the month
Name Identifier Basin Start Date
Juliette 14E NEP 29 September
Lekima 16W NWP 29 September

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.

Individual tropical cyclone summaries

Name: FITOW Identifier: 10W
Basin: NORTH-WEST PACIFIC
Start date: 29.08.2007 End date: 07.09.2007
1-minute MSW: 85 knots 10-minute MSW: 65 knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 21 19 17 15 13 10
Detection rate (%) 100 100 100 100 100 100
Mean DX 26 -45 -93 -97 -49 -44
Mean DY 14 -6 10 19 64 63
Mean AT 9 17 90 -3 -37 1
Mean CT 17 0 8 45 148 138
Track skill (%) **** 32 50 62 **** ****
Mean DPE 65 120 188 251 337 384
2006 DPE * 60 114 204 304 422 551
Intensity skill (%) **** 37 6 20 23 0

* DPE for all storms in the 2006 season in the NWP basin

Link to plot Plot of the storm's observed track and forecasts

On the whole, the turns in the track of Fitow were well predicted by the model. Track errors were below last season’s average and skill scores against CLIPER were high.

 

Name: GIL Identifier: 10E
Basin: NORTH-EAST PACIFIC
Start date: 29.08.2007 End date: 02.09.2007
1-minute MSW: 40 knots 10-minute MSW: - knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 4 2 0 0 0 0
Detection rate (%) 100 100 **** **** **** ****
Mean DX 19 -42 **** **** **** ****
Mean DY -14 39 **** **** **** ****
Mean AT -19 40 **** **** **** ****
Mean CT -9 37 **** **** **** ****
Track skill (5) **** 80 **** **** **** ****
Mean DPE 49 87 **** **** **** ****
2006 DPE * 51 103 185 265 366 430
Intensity skill (%) **** 0 **** **** **** ****

* DPE for all storms in the 2006 season in the NEP basin

Link to plot Plot of the storm's observed track

Gil only briefly became a tropical storm and only two forecasts were verified.

 

Name: HENRIETTE Identifier: 11W
Basin: NORTH-EAST PACIFIC
Start date: 30.08.2007 End date: 06.09.2007
1-minute MSW: 75 knots 10-minute MSW: -

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 12 10 8 6 4 2
Detection rate (%) 100 100 100 100 75 0
Mean DX 12 -12 -100 -268 -520 ****
Mean DY 7 5 -18 -113 -511 ****
Mean AT 2 11 8 -48 -373 ****
Mean CT 9 1 -81 -271 -629 ****
Track skill (%) 30 37 17 **** **** ****
Mean DPE 58 118 210 315 732 ****
2006 DPE * 51 103 185 265 366 430
Intensity skill (%) **** 80 -25 33 100 ****

* DPE for all storms in the 2006 season in the NEP basin

/weather/tropicalcyclone/tctracks/nhem07/04e.gif Plot of the storm's observed track

Early forecasts failed to turn Henriette towards the coast and resulted in some large track forecast errors, particularly at longer lead times. Skill scores were positive, but modest by T+72.

 

Name: FELIX Identifier: 06L
Basin: NORTH ATLANTIC
Start date: 30.08.2007 End date: 06.09.2007
1-minute MSW: 145 knots 10-minute MSW: - knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 8 6 4 2 0 0
Detection rate (%) 100 100 100 100 **** ****
Mean DX -2 9 14 33 **** ****
Mean DY 14 76 147 289 **** ****
Mean AT 2 -6 -17 -51 **** ****
Mean CT 14 71 147 288 **** ****
Track skill (%) **** 39 44 9 **** ****
Mean DPE 22 89 149 298 **** ****
2006 DPE * 46 109 213 322 425 529
Intensity skill (%) **** 0 -50 0 **** ****

* DPE for all storms in the 2006 season in the NAT basin

Link to plot Plot of the storm's observed track

There was a slight polewards bias in forecast tracks for Felix. However, track errors were lower than last season’s average and skill scores high at T+24 and T+48.

 

Name: DANAS Identifier: 11W
Basin: NORTH-WEST PACIFIC
Start date: 07.09.2007 End date: 11.09.2007
1-minute MSW: 60 knots 10-minute MSW: 50 knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 9 7 5 3 1 0
Detection rate (%) 100 100 100 100 100 ****
Mean DX -11 -41 -72 42 -362 ****
Mean DY -28 -10 89 100 -11 ****
Mean AT -38 -99 -81 24 -426 ****
Mean CT -3 1 -36 -16 59 ****
Track skill (%) **** 50 59 79 **** ****
Mean DPE 47 136 250 261 431 ****
2006 DPE * 60 114 204 304 422 551
Intensity skill (%) **** -14 20 33 -100 ****

* DPE for all storms in the 2006 season in the NWP basin

Link to plot Plot of the storm's observed track and forecasts

Track forecast errors were varied dependent on lead time. However, skill scores were very high.

 

Name: GABRIELLE Identifier: 08L
Basin: NORTH ATLANTIC
Start date: 08.09.2007 End date: 11.09.2007
1-minute MSW: 45 knots 10-minute MSW: - knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 5 3 1 0 0 0
Detection rate (%) 100 100 100 **** **** ****
Mean DX 15 -31 -27 **** **** ****
Mean DY -24 -26 -133 **** **** ****
Mean AT -32 -7 -139 **** **** ****
Mean CT 9 -19 8 **** **** ****
Track skill (%) **** 41 **** **** **** ****
Mean DPE 64 79 140 **** **** ****
2006 DPE * 46 109 213 322 425 529
Intensity skill (%) **** -33 -100 **** **** ****

* DPE for all storms in the 2006 season in the NWP basin

Link to plot Plot of the storm's observed track

Track forecast errors were below last season’s average for this short-lived storm.

 

Name: INGRID Identifier: 08L
Basin: NORTH ATLANTIC
Start date: 12.09.2007 End date: 17.09.2007
1-minute MSW: 40 knots 10-minute MSW: -

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 3 1 0 0 0 0
Detection rate (%) 100 100 **** **** **** ****
Mean DX 22 96 **** **** **** ****
Mean DY 15 33 **** **** **** ****
Mean AT -12 -71 **** **** **** ****
Mean CT 26 66 **** **** **** ****
Track skill (%) **** 16 **** **** **** ****
Mean DPE 49 98 **** **** **** ****
2006 DPE * 46 109 213 322 425 529
Intensity skill (%) **** 100 **** **** **** ****

* DPE for all storms in the 2006 season in the NAT basin

Link to plot Plot of the storm's observed track and forecasts

Ingrid persisted as a tropical depression for some time, but only briefly reached tropical storm status. Just one forecast was verified.

 

 

Name: HUMBERTO Identifier: 09L
Basin: NORTH ATLANTIC
Start date: 12.09.2007 End date: 13.09.2007
1-minute MSW: 75 knots 10-minute MSW: - knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 2 0 0 0 0 0
Detection rate (%) 100 **** **** **** **** ****
Mean DX 30 **** **** **** **** ****
Mean DY 6 **** **** **** **** ****
Mean AT 15 **** -8 **** **** ****
Mean CT 27 **** **** **** **** ****
Mean DPE 35 **** **** **** **** ****
2006 DPE * 46 109 213 322 425 529

* DPE for all storms in the 2006 season in the NAT basin

Link to plot Plot of the storm's observed track and forecasts

Humberto spun up to hurricane status and made landfall very quickly. Hence no forecasts were verified for this storm.

 

 

Name: NARI Identifier: 12W
Basin: NORTH-WEST PACIFIC
Start date: 12.09.2007 End date: 16.09.2007
1-minute MSW: 120 knots 10-minute MSW: 95 knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 7 5 3 1 0 0
Detection rate (%) 100 100 100 100 **** ****
Mean DX -18 92 120 281 **** ****
Mean DY -11 -87 -44 33 **** ****
Mean AT -3 -125 9 106 **** ****
Mean CT -12 74 129 265 **** ****
Track skill (%) **** 4 35 **** **** ****
Mean DPE 52 170 211 286 **** ****
2006 DPE * 60 114 204 304 422 551
Intensity skill (%) **** -20 -100 100 **** ****

* DPE for all storms in the 2006 season in the NWP basin

Link to plot Plot of the storm's observed track and forecasts

Some forecasts had a slow and right-of-track bias. Track forecast errors were above last season’s average at T+24, but below at other lead times.

 

Name: WIPHA Identifier: 13W
Basin: NORTH-WEST PACIFIC
Start date: 15.09.2007 End date: 19.09.2007
1-minute MSW: 135 knots 10-minute MSW: 100 knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 7 5 3 1 0 0
Detection rate (%) 100 100 100 100 **** ****
Mean DX 21 44 100 110 **** ****
Mean DY -2 -4 -74 -322 **** ****
Mean AT -8 -44 -111 -305 **** ****
Mean CT 5 23 -4 -159 **** ****
Track skill (%) **** 25 69 **** **** ****
Mean DPE 82 124 158 345 **** ****
2006 DPE * 60 114 204 304 422 551
Intensity skill (%) **** 60 100 -100 **** ****

* DPE for all storms in the 2006 season in the NWP basin

Link to plot Plot of the storm's observed track

Track forecast errors were variable depending on lead time. There was a slow bias in forecasts. Skill scores were positive.

Name: IVO Identifier: 12E
Basin: NORTH-EAST PACIFIC
Start date: 18.09.2007 End date: 23.09.2007
1-minute MSW: 70 knots 10-minute MSW: - knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 9 7 5 3 1 0
Detection rate (%) 100 100 100 100 100 ****
Mean DX -7 -4 45 123 42 ****
Mean DY -15 64 94 67 -211 ****
Mean AT -3 54 90 120 -126 ****
Mean CT -9 -31 -18 72 176 ****
Track skill (%) **** 6 42 79 **** ****
Mean DPE 40 98 164 196 217 ****
2006 DPE * 51 103 185 265 366 430
Intensity skill (%) **** 43 60 100 100 ****

* DPE for all storms in the 2006 season in the NEP basin

Link to plot Plot of the storm's observed track

Track forecast errors were below last season’s average for this storm and skill scores high at longer lead times.

 

Name: Identifier: 13E
Basin: NORTH-EAST PACIFIC
Start date: 19.09.2007 End date: 20.09.2007
1-minute MSW: 30 knots 10-minute MSW: -

 

Link to plot Plot of the storm's observed track

There are no verification statistics or forecast plot for this tropical cyclone since its 1-minute averaged winds did not reach tropical storm strength.

 

Name: Identifier: 14W
Basin: NORTH-WEST PACIFIC
Start date: 20.09.2007 End date: 21.09.2007
1-minute MSW: 30 knots 10-minute MSW: -

 

Link to plot Plot of the storm's observed track

There are no verification statistics or forecast plot for this tropical cyclone since its 1-minute averaged winds did not reach tropical storm strength.

 

Name: Identifier: 10L
Basin: NORTH ATLANTIC
Start date: 21.09.2007 End date: 22.09.2007
1-minute MSW: 30 knots 10-minute MSW: -

 

Link to plot Plot of the storm's observed track

There are no verification statistics or forecast plot for this tropical cyclone since its 1-minute averaged winds did not reach tropical storm strength.

 

Name: FRANCISCO Identifier: 15W
Basin: NORTH-WEST PACIFIC
Start date: 23.09.2007 End date: 25.09.2007
1-minute MSW: 45 knots 10-minute MSW: 45 knots

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 3 1 0 0 0 0
Detection rate (%) 100 100 **** **** **** ****
Mean DX 21 52 **** **** **** ****
Mean DY 15 100 **** **** **** ****
Mean AT -22 -52 **** **** **** ****
Mean CT 18 100 **** **** **** ****
Mean DPE 38 113 **** **** **** ****
2006 DPE * 60 114 204 304 422 551
Intensity skill (%) **** 100 **** **** **** ****

* DPE for all storms in the 2006 season in the NWP basin

Link to plot Plot of the storm's observed track

Francisco was short-lived and just one forecast was verified.

 

 

Name: JERRY Identifier: 11L
Basin: NORTH ATLANTIC
Start date: 23.09.2007 End date: 25.09.2007
1-minute MSW: 40 knots 10-minute MSW: -

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 3 1 0 0 0 0
Detection rate (%) 100 100 **** **** **** ****
Mean DX 9 -105 **** **** **** ****
Mean DY -7 111 **** **** **** ****
Mean AT -9 -15 **** **** **** ****
Mean CT 20 -152 **** **** **** ****
Mean DPE 35 **** **** **** **** ****
2006 DPE * 46 109 213 322 425 529
Intensity skill (%) **** -100 **** **** **** ****

* DPE for all storms in the 2006 season in the NAT basin

Link to plot Plot of the storm's observed track and forecasts

Jerry only briefly reached tropical storm status and just one forecast was verified.

Name: KAREN Identifier: 12L
Basin: NORTH ATLANTIC
Start date: 25.09.2007 End date: 29.09.2007
1-minute MSW: 60 knots# 10-minute MSW: -

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 8 6 4 2 0 0
Detection rate (%) 100 100 100 100 **** ****
Mean DX 7 35 54 -70 **** ****
Mean DY 19 84 173 178 **** ****
Mean AT -6 -11 3 22 **** ****
Mean CT 37 81 181 162 **** ****
Track skill (%) **** 16 26 74 **** ****
Mean DPE 69 114 198 223 **** ****
2006 DPE * 46 109 213 322 425 529
Intensity skill (%) **** 0 0 0 **** ****

* DPE for all storms in the 2006 season in the NAT basin
# Karen may be upgraded to a hurricane in post season reanalysis

Link to plot Plot of the storm's observed track and forecasts

Track forecast errors were near to or below last season’s average for this storm. There was a right-of-track bias in forecasts and skills cores were positive.

 

 

Name: LORENZO Identifier: 13L
Basin: NORTH ATLANTIC
Start date: 25.09.2007 End date: 28.09.2007
1-minute MSW: 65 knots 10-minute MSW: -

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 1 0 0 0 0 0
Detection rate (%) 100 **** **** **** **** ****
Mean DX 25 **** **** **** **** ****
Mean DY 0 **** **** **** **** ****
Mean AT -24 **** **** **** **** ****
Mean CT -2 **** **** **** **** ****
Mean DPE 25 **** **** **** **** ****
2006 DPE * 46 109 213 322 425 529

* DPE for all storms in the 2006 season in the NAT basin
# Karen may be upgraded to a hurricane in post season reanalysis

Link to plot Plot of the storm's observed track and forecasts

Lorenzo spun up from a tropical depression to hurricane and made landfall very quickly so no forecasts were verified.

 

 

Name: MELISSA Identifier: 14L
Basin: NORTH ATLANTIC
Start date: 28.09.2007 End date: 30.09.2007
1-minute MSW: 40 knots 10-minute MSW: -

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 2 0 0 0 0 0
Detection rate (%) 100 **** **** **** **** ****
Mean DX 0 **** **** **** **** ****
Mean DY 73 **** **** **** **** ****
Mean AT 36 **** **** **** **** ****
Mean CT 62 **** **** **** **** ****
Mean DPE 75 **** **** **** **** ****
2006 DPE * 46 109 213 322 425 529

* DPE for all storms in the 2006 season in the NAT basin
# Karen may be upgraded to a hurricane in post season reanalysis

Link to plot Plot of the storm's observed track and forecasts

Melissa only briefly attained tropical storm status and no forecasts were verified.

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: 19
Number of storms used in statistics below: 16

Table of mean error statistics
  T+0 T+24 T+48 T+72 T+96 T+120
Possibly verified 104 73 50 33 19 12
Detection rate (%) 100 100 100 100 95 83
Mean DX 9 -6 -32 -68 -140 -44
Mean DY 2 14 37 23 -52 63
Mean AT -5 -12 23 -6 -120 1
Mean CT 10 16 15 2 15 138
Track skill (%) **** 30 47 57 **** ****
Mean DPE 54 117 192 263 401 384
2006 DPE * 57 112 203 303 422 537
Intensity skill (%) **** 26 0 27 33 0

* DPE for all northern hemisphere storms in 2006 season

Despite a high number of tropical cyclones forming this month, many were weak or short lived, so the number of verifiable forecasts at longer lead times was quite small. Overall, track forecast errors were near to or below last season’s average. Skill scores against CLIPER were high and there were no significant biases overall. The overall intensity tendency skill score was 18%.


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