Tropical cyclone activity
| Tropical cyclones ending during the month | |||||||
|---|---|---|---|---|---|---|---|
| NWP | NEP | NAT | NI | SWI | AUS | Total | |
| Total number ending during the month | 1 | 2 | 1 | 3 | 0 | 0 | 6 |
| Tropical cyclones active during the month | ||||||
|---|---|---|---|---|---|---|
| Name | Identifier | Basin | Start date | End date | 1-minute MSW | 10-minute MSW |
| Barbara | 02E | NEP | 29 May | 02 June | 45 | - |
| Barry | 02L | NAT | 01 June | 02 June | 45 | - |
| Gonu | 02A | NI | 02 June | 07 June | 140 | 125 |
| - | 03E | NEP | 11 June | 13 June | 30 | - |
| - | 03B | NI | 21 June | 26 June | 50 | 30 |
| - | 04B | NI | 28 June | 29 June | 45 | 30 |
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.
Tropical cyclones still active at the end of the month
None
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: BARBARA Identifier: 02E
Basin: NORTH-EAST PACIFIC
Start date: 29.05.2007 End
date: 02.06.2007
1-minute MSW: 45 knots
10-minute MSW: -
| 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 | 0 | -145 | -346 | -463 | **** | **** |
| Mean DY | -38 | 2 | 41 | 11 | **** | **** |
| Mean AT | -10 | -132 | -296 | -371 | **** | **** |
| Mean CT | 47 | -36 | -177 | -278 | **** | **** |
| Track skill (%) | **** | 33 | 17 | **** | **** | **** |
| Mean DPE | 57 | 153 | 351 | 464 | **** | **** |
| 2006 DPE * | 51 | 103 | 185 | 265 | 366 | 430 |
| Intensity skill (%) | **** | 60 | 33 | -100 | **** | **** |
* DPE for all storms in the 2006 season in the NEP basin
 |
Plot of the storm's observed track and forecasts |
The model had a slow and northwards bias which resulted in track forecast errors above last season’s average. However, the model showed skill over CLIPER.
Name: BARRY Identifier: 02L
Basin: NORTH ATLANTIC
Start date: 01.06.2007 End date: 02.06.2007
1-minute MSW: 45 knots 10-minute MSW: -
| 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 | -25 | **** | **** | **** | **** | **** |
| Mean DY | 128 | **** | **** | **** | **** | **** |
| Mean AT | 94 | **** | **** | **** | **** | **** |
| Mean CT | -98 | **** | **** | **** | **** | **** |
| Mean DPE | 132 | **** | **** | **** | **** | **** |
| 2006 DPE * | 46 | 109 | 213 | 322 | 425 | 529 |
* DPE for all storms in the 2006 season in the NAT basin
 |
Plot of the storm's observed track and forecasts |
Barry was a short-lived storm and no forecasts were verified.
Name: GONU Identifier: 02A
Basin: NORTH INDIAN (Arabian Sea)
Start date: 02.06.2007 End date: 07.06.2007
1-minute MSW: 140 knots 10-minute MSW: 125 knots
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 11 | 9 | 7 | 5 | 3 | 1 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 6 | 30 | 49 | 34 | 114 | 417 |
| Mean DY | 1 | 5 | -59 | -206 | -423 | -267 |
| Mean AT | 6 | -35 | -81 | -131 | -412 | -469 |
| Mean CT | 4 | 21 | -13 | -121 | -179 | 172 |
| Track skill (%) | **** | 41 | 55 | 62 | **** | **** |
| Mean DPE | 74 | 106 | 182 | 269 | 454 | 500 |
| 2006 DPE * | 93 | 164 | 254 | 443 | 940 | 897 |
| Intensity skill (%) | **** | -11 | 43 | 60 | 33 | -100 |
* DPE for all storms in the 2006 season in the NI basin
 |
Plot of the storm's observed track and forecasts |
Gonu was an exceptionally strong cyclone for the Arabian Sea. Track forecast errors were below last season’s average and skill scores against CLIPER were high. The model did a generally good job in predicting the track of Gonu into the Gulf of Oman given that some other model predictions took Gonu either into Oman itself or turned it northwards towards Iran much sooner than actually occurred.
Name: - Identifier: 03E
Basin: NORTH-EAST PACIFIC
Start date: 11.06.2007 End date: 13.06.2007
1-minute MSW: 30 knots 10-minute MSW: -
There are no verification statistics or forecast plot for this tropical
cyclone since its 1-minute averaged winds did not reach tropical storm
strength.
A plot of
the depression's observed track and forecasts.
Name: - Identifier: 03B
Basin: NORTH INDIAN
Start date: 21.06.2007 End
date: 26.06.2007
1-minute MSW: 50 knots 10-minute MSW: 30
knots
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 5 | 1 | 0 | 0 | 2 | 1 |
| Detection Rate (%) | 100 | 100 | **** | **** | 100 | 100 |
| Mean DX | 14 | -20 | **** | **** | -278 | -280 |
| Mean DY | -51 | -222 | **** | **** | 128 | -56 |
| Mean AT | -56 | -88 | **** | **** | 278 | 218 |
| Mean CT | -4 | -201 | **** | **** | -68 | -185 |
| Track skill (%) | **** | -9 | **** | **** | **** | **** |
| Mean DPE | 108 | 220 | **** | **** | 308 | 286 |
| 2006 DPE * | 93 | 164 | 254 | 443 | 940 | 897 |
| Intensity skill (%) | **** | 100 | **** | **** | **** | -100 |
* DPE for all storms in the 2006 season in the NI basin
 |
Plot of the storm's observed track and forecasts |
03B was not given a name by the India Met. Department who have official responsibility for naming in this region. However, the Pakistan Met. Department chose to use the name Yemyin, which was subsequently widely quoted in the media.
03B initially formed in the Bay of Bengal and made landfall over India. The remnants emerged into the Arabian Sea some time later and reformed before landfall over Pakistan. Forecast errors were calculated when 03B was at tropical storm strength only. The prediction of reformation over the Arabian Sea was very well handled by the model.
Name: - Identifier: 04B
Basin: NORTH INDIAN
Start date: 28.06.2007 End date: 29.06.2007
1-minute MSW: 45 knots 10-minute MSW: 30 knots
| 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 | 42 | 62 | **** | **** | **** | **** |
| Mean DY | 15 | 22 | **** | **** | **** | **** |
| Mean AT | -60 | -35 | **** | **** | **** | **** |
| Mean CT | 28 | 54 | **** | **** | **** | **** |
| Mean DPE | 83 | 65 | **** | **** | **** | **** |
| 2006 DPE * | 93 | 164 | 254 | 443 | 940 | 897 |
| Intensity skill (%) | **** | 100 | **** | **** | **** | **** |
* DPE for all storms in the 2006 season in the NI basin
 |
Plot of the storm's observed track and forecasts |
04B was a short-lived storm and just one forecast was 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: 6
Number of storms used in statistics below: 5
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 28 | 16 | 10 | 6 | 5 | 2 |
| Detection Rate (%) | 100 | 100 | 100 | 100 | 100 | 100 |
| Mean DX | 7 | -26 | -69 | -49 | -43 | 69 |
| Mean DY | -8 | -9 | -29 | -170 | -202 | -162 |
| Mean AT | -11 | -69 | -146 | -171 | -136 | -126 |
| Mean CT | 13 | -9 | -62 | -147 | -134 | -7 |
| Track skill (%) | **** | 33 | 43 | 62 | **** | **** |
| Mean DPE | 81 | 125 | 232 | 302 | 395 | 393 |
| 2006 DPE * | 57 | 112 | 203 | 303 | 422 | 537 |
| Intensity skill (%) | **** | 25 | 40 | 33 | 33 | -100 |
* DPE for all northern hemisphere storms in 2006 season
Track forecast errors were near to last season’s average and skill scores against CLIPER were good. There was a slow and slight left-of-track bias in forecasts. The overall intensity tendency skill score was 24%.
Tropical cyclone activity in the southern hemisphere during 2006-7 season
| Tropical cyclone activity | |||
|---|---|---|---|
| SWI | AUS | TOTAL | |
| Tropical Depressions | 0(3) | 2(0) | 2(3) |
| Tropical Storms | 3(3) | 8(5) | 11(8) |
| Hurricanes/Typhoons | 7(2) | 5(10) | 12(12) |
| Total | 10(8) | 15(15) | 25(23) |
( ) The number in brackets indicates the figure for the 2005-6 season. Definitions based on RSMC 10-minute average wind speeds are used.
Summary of all Southern Hemisphere Storms in 2006-7
Mean error statistics for all Southern Hemisphere storms that occurred in the 2006-7 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:- 25
| MEAN ERROR STATISTICS | ||||||
|---|---|---|---|---|---|---|
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | |
| Possibly Verified | 183 | 136 | 98 | 70 | 48 | 34 |
| Detection Rate (%) | 100 | 100 | 100 | 97 | 90 | 91 |
| Mean DX |
5 | -44 | -182 | -337 | -482 | -517 |
| Mean DY |
5 | 27 | -4 | -54 | -165 | -288 |
| Mean AT |
2 | -3 | -9 | 3 | -5 | -2 |
| Mean CT |
10 | -11 | -96 | -237 | -495 | -471 |
| Skill (%) | **** | 29 | 18 | 15 | **** | **** |
| * 2005-6 Skill (%) | **** | 39 | 40 | 38 | **** | **** |
| Mean DPE | 54 | 136 | 298 | 496 | 727 | 870 |
| * 2005-6 DPE | 67 | 140 | 237 | 379 | 559 | 571 |
| Intensity skill (%) | **** | 24 | 8 | 24 | -2 | 42 |
* Real time figures for all Southern Hemisphere storms in 2005-6.
Southern Hemisphere warning centres recorded 25 tropical cyclones in the 2006-7 season. This is slightly more than the previous season. There was a marked increase in the proportion of strong cyclones in the South-West Indian Ocean region. However, this was accompanied by a decrease in the proportion of strong cyclones in the Australian region.
Observed tracks of this season’s TCs.
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 higher than the last few seasons at all lead times above T+24. In the Australian basin forecast errors were higher at all lead times – particularly the longer lead times.
Skill against CLIPER was lower than the last two season at all lead times. Cross track errors showed a right-of-track bias, particularly at long lead times. Along track errors reduced to very small values this season.
Overall, it was a poor season for track forecasting. However, the figures are dominated by two tropical cyclones, which were, at times, very poorly forecast by the model. These were Tropical Cyclone Dora (see February summary) and Tropical Cyclone George (see March summary). With these storms excluded the season’s track forecast errors are similar to or lower than the last few seasons.
Intensity tendency skill score averaged for all forecasts was 18% in the 2006-7 Southern Hemisphere season. This compares to 31% and 30% for the previous two seasons.
A revised Southern Hemisphere summary will be issued once best track data has been collected later in the year.
Forecast Positional Errors:
SWI Combined
southern hemisphere
Southern
hemisphere skill
Southern
hemisphere cross track errors
Southern
hemisphere along track errors
