Verification of tracks made on Helene using GEFS mean fields
I made 21 tracks about Hurricane Helene. Additionally, within 384
hours of cyclogenesis, there were four instances, when I missed
cyclogenesis entirely. Timing and position of cyclogenesis was very well predicted weeks in advance. At shorter lead times, there was only a little improvement. Track forecast accuracy was variable, as was predicted peak intensity. Longevity of the cyclone also varied greatly.
As of this analysis, best track positions are available September 6, 00Z thru September 16, 12Z, and as such, position comparisons are possible only for this timespan.
Since I give only SSHS categories in my tracks, I don't calculate intensity errors in units of speed, but in categories. For this purpose, I define tropical or subtropical storms as "Category 0", tropical or subtropical depressions as "Category -1" and non-existence of a tropical or subtropical cyclone as "Category -2".
In the 21 tracks, formation times ranged between September 7, 12Z and September 11, 00Z. Average was September 8, 11Z and median was September 8, 06Z.
In the 25 cases (21 tracks and 4 complete misses), peak intensity ranged between Category -2 and Category 5. Average was Category 1.72 and median was Category 2.
In the 21 tracks, dissipation times ranged between September 10, 18Z and October 26, 12Z. Average was September 22, 01Z and median was September 15, 00Z.
At the lead time of 1 day (24 hours), there were 0 hits, 0 false detections and 0 misses. No available position comparisons.
At the lead time of 2 days (48 hours), there were 1 hits, 0 false detections and 0 misses. 1 available position comparison produces an average error of 134 nautical miles.
At the lead time of 3 days (72 hours), there were 1 hits, 0 false detections and 1 misses. 1 available position comparison produces an average error of 214 nautical miles.
At the lead time of 4 days (96 hours), there were 3 hits, 0 false detections and 0 misses. 3 available position comparisons produce an average error of 174 nautical miles.
At the lead time of 5 days (120 hours), there were 4 hits, 0 false detections and 0 misses. 4 available position comparisons produce an average error of 219 nautical miles.
At the lead time of 6 days (144 hours), there were 5 hits, 0 false detections and 0 misses. 5 available position comparisons produce an average error of 216 nautical miles.
At the lead time of 7 days (168 hours), there were 5 hits, 0 false detections and 2 misses. 5 available position comparisons produce an average error of 214 nautical miles.
At the lead time of 8 days (192 hours), there were 4 hits, 0 false detections and 3 misses. 5 available position comparisons produce an average error of 298 nautical miles.
At the lead time of 9 days (216 hours), there were 3 hits, 0 false detections and 6 misses. 5 available position comparisons produce an average error of 472 nautical miles.
At the lead time of 10 days (240 hours), there were 4 hits, 0 false detections and 7 misses. 6 available position comparisons produce an average error of 540 nautical miles.
At the lead time of 11 days (264 hours), there were 8 hits, 0 false detections and 4 misses. 8 available position comparisons produce an average error of 510 nautical miles.
At the lead time of 12 days (288 hours), there were 12 hits, 1 false detections and 1 misses. 13 available position comparisons produce an average error of 539 nautical miles.
At the lead time of 13 days (312 hours), there were 11 hits, 2 false detections and 2 misses. 12 available position comparisons produce an average error of 508 nautical miles.
At the lead time of 14 days (336 hours), there were 13 hits, 2 false detections and 2 misses. 13 available position comparisons produce an average error of 380 nautical miles.
At the lead time of 15 days (360 hours), there were 14 hits, 3 false detections and 2 misses. 15 available position comparisons produce an average error of 473 nautical miles.
At the lead time of 16 days (384 hours), there were 11 hits, 4 false detections and 7 misses. 11 available position comparisons produce an average error of 409 nautical miles.
Here are the tracks once again.
August 23, 06Z run:
Beginning with August 23, 12Z, run, coloration scheme changed to the
following, and this legend ceased to be included in every track.
August 24, 06Z run:
August 24, 18Z run:
August 25, 06Z run:
August 25, 12Z run:
August 26, 12Z run:
August 26, 18Z run:
August 27, 06Z run:
August 27, 12Z run:
August 27, 18Z run:
August 28, 06Z run:
August 28, 18Z run:
August 29, 18Z run:
August 30, 12Z run:
August 31, 18Z run:
September 1, 12Z run:
September 2, 12Z run:
September 3, 12Z run:
September 4, 12Z run:
September 5, 06Z run:
September 6, 06Z run:
The complete misses were from following GEFS runs:
August 22, 18Z
August 23, 12Z
August 23, 18Z
August 29, 12Z
As of this analysis, best track positions are available September 6, 00Z thru September 16, 12Z, and as such, position comparisons are possible only for this timespan.
Since I give only SSHS categories in my tracks, I don't calculate intensity errors in units of speed, but in categories. For this purpose, I define tropical or subtropical storms as "Category 0", tropical or subtropical depressions as "Category -1" and non-existence of a tropical or subtropical cyclone as "Category -2".
In the 21 tracks, formation times ranged between September 7, 12Z and September 11, 00Z. Average was September 8, 11Z and median was September 8, 06Z.
In the 25 cases (21 tracks and 4 complete misses), peak intensity ranged between Category -2 and Category 5. Average was Category 1.72 and median was Category 2.
In the 21 tracks, dissipation times ranged between September 10, 18Z and October 26, 12Z. Average was September 22, 01Z and median was September 15, 00Z.
At the lead time of 1 day (24 hours), there were 0 hits, 0 false detections and 0 misses. No available position comparisons.
At the lead time of 2 days (48 hours), there were 1 hits, 0 false detections and 0 misses. 1 available position comparison produces an average error of 134 nautical miles.
At the lead time of 3 days (72 hours), there were 1 hits, 0 false detections and 1 misses. 1 available position comparison produces an average error of 214 nautical miles.
At the lead time of 4 days (96 hours), there were 3 hits, 0 false detections and 0 misses. 3 available position comparisons produce an average error of 174 nautical miles.
At the lead time of 5 days (120 hours), there were 4 hits, 0 false detections and 0 misses. 4 available position comparisons produce an average error of 219 nautical miles.
At the lead time of 6 days (144 hours), there were 5 hits, 0 false detections and 0 misses. 5 available position comparisons produce an average error of 216 nautical miles.
At the lead time of 7 days (168 hours), there were 5 hits, 0 false detections and 2 misses. 5 available position comparisons produce an average error of 214 nautical miles.
At the lead time of 8 days (192 hours), there were 4 hits, 0 false detections and 3 misses. 5 available position comparisons produce an average error of 298 nautical miles.
At the lead time of 9 days (216 hours), there were 3 hits, 0 false detections and 6 misses. 5 available position comparisons produce an average error of 472 nautical miles.
At the lead time of 10 days (240 hours), there were 4 hits, 0 false detections and 7 misses. 6 available position comparisons produce an average error of 540 nautical miles.
At the lead time of 11 days (264 hours), there were 8 hits, 0 false detections and 4 misses. 8 available position comparisons produce an average error of 510 nautical miles.
At the lead time of 12 days (288 hours), there were 12 hits, 1 false detections and 1 misses. 13 available position comparisons produce an average error of 539 nautical miles.
At the lead time of 13 days (312 hours), there were 11 hits, 2 false detections and 2 misses. 12 available position comparisons produce an average error of 508 nautical miles.
At the lead time of 14 days (336 hours), there were 13 hits, 2 false detections and 2 misses. 13 available position comparisons produce an average error of 380 nautical miles.
At the lead time of 15 days (360 hours), there were 14 hits, 3 false detections and 2 misses. 15 available position comparisons produce an average error of 473 nautical miles.
At the lead time of 16 days (384 hours), there were 11 hits, 4 false detections and 7 misses. 11 available position comparisons produce an average error of 409 nautical miles.
Here are the tracks once again.
August 23, 06Z run:
August 24, 06Z run:
The complete misses were from following GEFS runs:
August 22, 18Z
August 23, 12Z
August 23, 18Z
August 29, 12Z
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