Tropical cyclone verification northern hemisphere 2024
A summary of tropical cyclone activity in the Northern Hemisphere for the 2024 season together with an assessment of the performance of the Met Office global model in predicting the track and intensity of these tropical cyclones.
1. Introduction
A summary of tropical cyclone activity in the Northern Hemisphere for the 2024 season is presented below together with an assessment of the performance of the Met Office global model in predicting the track and intensity of these tropical cyclones.
Tropical cyclones are experienced in the North Pacific, North Atlantic and North Indian Oceans and nearby tropical seas with occasional tropical or subtropical storms in the Mediterranean Sea. For the purpose of tropical cyclone verification the northern hemisphere is divided in to five basins; the North-West Pacific (west of 180° E to the Malay Peninsula), the North-East Pacific (east of 180° E), the North Atlantic, the North Indian Ocean (west of the Malay Peninsula) and the Mediterranean Sea. Mean error statistics for the four main basins are presented together with a table of statistics for the whole Northern Hemisphere. Verification is performed at 12-hour intervals up to forecast time T+168, although statistics are only presented at 24-hour intervals in this report. The global model resolution in operation was 0.140625° x 0.09375° x 70 levels. This is equivalent to a horizontal resolution of 16 km × 10 km at the equator.
Tropical cyclone forecast verification - measures of error
Advisory positions received in real time from RSMC Tokyo, JTWC Hawaii, NHC Miami and CPHC Honolulu are used as verifying observations of storm location. Best track data from these centres will be obtained once they become available. Past experience shows that use of best track rather than real time data usually only makes minor differences to seasonal error statistics. Some mean error statistics for last season are also included for the purposes of a comparison. Forecast tracks are only verified when a depression reaches tropical storm status.
2. Tropical cyclone activity
| NWP | NEP | NAT | NI | MED | TOTAL | |
|---|---|---|---|---|---|---|
| Tropical depressions (<34 knots) | 5 (2) | 2 (3) | 0 (1) | 0 (0) | 0 (0) | 7 (6) |
| Tropical storms (34-63 knots) | 8 (5) | 8 (7) | 7 (13) | 3 (4) | 2 (1) | 28 (30) |
| Hurricanes/typhoons (>63 knots) | 15 (11) | 5 (10) | 11 (7) | 1 (4) | 0 (0) | 32 (32) |
| Total | 28 (18) | 15 (20) | 18 (21) | 4 (8) | 2 (1) | 67 (68) |
Categories assigned based on 1-minute averaged winds
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)
MED : Mediterranean Sea
The number in brackets indicates the figure for the 2023 season.
3. Summary of northern hemisphere storms
3.1 North-west Pacific basin storms
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | T+168 | |
| Possibly verified | 221 | 175 | 139 | 109 | 77 | 48 | 22 | 10 |
| Detection rate (%) | 100 | 99 | 99 | 99 | 99 | 88 | 82 | 40 |
| AT error (km) | 7 | 7 | -4 | -46 | -67 | 56 | 176 | -161 |
| CT error (km) | 4 | 7 | 16 | 44 | 102 | 196 | 313 | 528 |
| Track skill (%) | ***** | 64 | 78 | 78 | ***** | ***** | ***** | ***** |
| * 2019-23 skill (%) | ***** | 61 | 68 | 68 | ***** | ***** | ***** | ***** |
| DPE (km) | 42 | 74 | 107 | 163 | 264 | 437 | 607 | 808 |
| * 2019-23 DPE (km) | 32 | 68 | 128 | 202 | 298 | 402 | 529 | 659 |
| Central pressure bias (mb) | 4.0 | 10.9 | 17.0 | 21.3 | 22.3 | 22.5 | 24.2 | 36.2 |
* 5-year running mean DPE and skill for all north-west Pacific storms 2019-23
Plot of the observed tracks of all storms in the north-west Pacific basin
Track forecast errors in the north-west Pacific basin
Track forecast skill in the north-west Pacific basin
Total storm activity was much higher than 2023, although the number of verified forecasts was little different. Track forecast errors were below the 5-year running mean up to 96 hours, but above the mean at longer lead times. The central pressure bias grew with forecast lead time indicating forecast intensities were too weak.
3.2 North-east Pacific basin storms
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | T+168 | |
| Possibly verified | 107 | 80 | 59 | 45 | 32 | 23 | 16 | 11 |
| Detection rate (%) | 99 | 94 | 97 | 98 | 97 | 87 | 81 | 73 |
| AT error (km) | 5 | 19 | 67 | 111 | 128 | 123 | 229 | 313 |
| CT error (km) | -5 | 4 | 2 | -23 | -38 | -112 | -38 | -29 |
| Track skill (%) | ***** | 47 | 52 | 48 | ***** | ***** | ***** | ***** |
| * 2019-23 skill (%) | ***** | 52 | 64 | 68 | ***** | ***** | ***** | ***** |
| DPE (km) | 37 | 74 | 128 | 209 | 267 | 392 | 508 | 703 |
| * 2019-23 DPE (km) | 33 | 71 | 125 | 187 | 251 | 306 | 413 | 526 |
| Central pressure bias (mb) | 1.3 | 5.2 | 9.9 | 11.1 | 13.0 | 13.4 | 11.2 | 11.6 |
* 5-year running mean DPE and skill for all north-east Pacific storms for 2019-23
Plot of the observed tracks of all storms in the north-east Pacific basin
Track forecast errors in the north-east Pacific basin
Track forecast skill in the north-east Pacific basin
Activity was lower than 2023. Track forecast errors were near to the 5-year running mean at lead times up to 96 hours. There was a weak bias in central pressure forecasts, but by a smaller margin than in 2023.
3.3 North Atlantic basin storms
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | T+168 | |
| Possibly verified | 159 | 125 | 95 | 68 | 49 | 33 | 23 | 15 |
| Detection rate (%) | 100 | 99 | 99 | 99 | 98 | 91 | 78 | 53 |
| AT error (km) | -3 | -11 | -19 | -34 | -49 | -104 | -217 | -404 |
| CT error (km) | 1 | -9 | -32 | -45 | -59 | -113 | -124 | -101 |
| Track skill (%) | ***** | 68 | 75 | 75 | ***** | ***** | ***** | ***** |
| * 2019-23 skill (%) | ***** | 68 | 73 | 71 | ***** | ***** | ***** | ***** |
| DPE (km) | 26 | 57 | 101 | 150 | 231 | 295 | 396 | 460 |
| * 2019-23 DPE (km) | 30 | 64 | 117 | 194 | 273 | 379 | 536 | 672 |
| Central pressure bias (mb) | 4.1 | 10.7 | 15.0 | 16.3 | 12.2 | 11.5 | 7.7 | 6.9 |
* 5-year running mean DPE and skill for all North Atlantic storms for 2019-23
Plot of the observed tracks of all storms in the North Atlantic basin
Track forecast errors in the North Atlantic basin
Track forecast skill in the North Atlantic basin
2024 saw a smaller total number of storms than 2023, but more hurricanes. Track forecast errors were lower than the 5-year running mean at all lead times. There was a weak bias in forecasts, but this reduced at longer lead times.
3.4 North Indian Basin Storms
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | T+168 | |
| Possibly verified | 20 | 12 | 4 | ***** | ***** | ***** | ***** | ***** |
| Detection rate (%) | 100 | 100 | 100 | ***** | ***** | ***** | ***** | ***** |
| AT error (km) | -8 | -11 | 24 | ***** | ***** | ***** | ***** | ***** |
| CT error (km) | 9 | 34 | 45 | ***** | ***** | ***** | ***** | ***** |
| Track skill (%) | ***** | 70 | ***** | ***** | ***** | ***** | ***** | ***** |
| * 2019-23 skill (%) | ***** | 51 | 55 | 60 | ***** | ***** | ***** | ***** |
| DPE (km) | 38 | 58 | 65 | ***** | ***** | ***** | ***** | ***** |
| * 2019-23 DPE (km) | 36 | 70 | 124 | 181 | 249 | 353 | 465 | 455 |
| Central pressure bias (mb) | 1.1 | 2.5 | 3.8 | ***** | ***** | ***** | ***** | ***** |
* 5-year running mean DPE and skill for all North Indian storms for 2019-23
Plot of the observed tracks of all storms in the North Indian basin
Track forecast errors in the North Indian basin
Track forecast skill in the North Indian basin
There were few storm in 2024 with none producing forecasts beyond 60 hours. Track forecast errors were low for the forecasts which were verified. There was a small weak bias in forecast central pressure.
3.5 Combined statistics for whole northern hemisphere
| T+0 | T+24 | T+48 | T+72 | T+96 | T+120 | T+144 | T+168 | |
| Possibly verified | 512 | 394 | 298 | 223 | 159 | 105 | 62 | 37 |
| Detection rate (%) | 100 | 98 | 98 | 98 | 97 | 88 | 79 | 54 |
| AT error (km) | 3 | 3 | 5 | -11 | -22 | 19 | 46 | -69 |
| CT error (km) | 1 | 2 | -2 | 4 | 24 | 28 | 59 | 53 |
| Track skill (%) | ***** | 63 | 74 | 74 | ***** | ***** | ***** | ***** |
| * 2019-23 skill (%) | ***** | 61 | 68 | 69 | ***** | ***** | ***** | ***** |
| DPE (km) | 36 | 68 | 108 | 168 | 254 | 381 | 503 | 627 |
| * 2019-23 DPE (km) | 32 | 68 | 124 | 195 | 277 | 373 | 511 | 642 |
| Central pressure bias (mb) | 3.3 | 9.5 | 14.8 | 17.7 | 17.3 | 16.9 | 14.7 | 14.6 |
* 5-year running mean DPE and skill for all northern hemisphere storms for 2019-23
The number of storms was similar to 2024, but they were not so long-lived resulting in a lower number of verifiable forecasts at longer lead times.
Track forecast errors were near to or below the 5-year running mean. Along and cross-track biases were mostly quite small. Detection percentages were dropped off markedly at longer lead times.
Track forecast errors for the whole northern hemisphere
Track forecast skill for the whole northern hemisphere
Cross-track errors for the whole northern hemisphere
Along-track errors for the whole northern hemisphere
The 5-year running mean of track forecast errors continues to increase slightly at longer lead times.
5-year running mean track forecast errors for the whole northern hemisphere
The intensity bias as measured by central pressure was positive (weak bias) and growing with lead time up to 84 hours. Similarly 10m winds had a weak bias which increased with lead time to 84 hours, but reduced at longer lead times. This is similar to what was seen in the last couple of years following the introduction of global model configuration GC4 in May 2022. Mean absolute errors for central pressure were higher than recent years at shorter lead times, but leveled off at longer lead times. For 10m winds the mean absolute errors were similar to the last two years.
Central pressure forecast bias for the whole northern hemisphere
Peak 10m wind forecast bias for the whole northern hemisphere
Central pressure forecast mean abosolute error for the whole northern hemisphere
Peak 10m wind forecast mean absolute error for the whole northern hemisphere
4. Further tropical cyclone information
The Met Office tropical cyclone web pages contain information on tropical cyclone forecasting at the Met Office. Monthly updates of tropical cyclone activity and forecasts are made, together with observed and forecast information of recent storms, track and intensity prediction error statistics, lists of names and real time tropical cyclone forecast guidance.
For further information on tropical cyclone forecasting email the Met Office.
