Verification of tracks made of Gabrielle using GEFS mean fields

October 21, 2019

I made six tracks of Tropical Storm Gabrielle. Additionally, within 384 hours of cyclogenesis, there were six instances, when I missed cyclogenesis entirely. Timing of cyclogenesis was close to correct, but dissipation time varied greatly. Peak intensity also varied, though on average, it was pretty accurate.

As of this analysis, best track positions are available August 31, 12Z thru September 10, 06Z, 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 six tracks, formation times ranged between September 2, 00Z and September 5, 06Z. Average was September 3, 02Z and median was September 2, 06Z.

In the twelve cases (6 tracks and 6 complete misses), peak intensity ranged between Category -2 and Category 3. Average was Category -0.42 and median was Category -1.5.

In the six tracks, dissipation times ranged between September 7, 12Z and September 21, 06Z. Average was September 12, 14Z and median was September 10, 18Z.

At the lead time of 1 day (24 hours), there were 0 hits, 1 false detection and 0 misses. 1 available position comparison produces an average error of 58 nautical miles.

At the lead time of 2 days (48 hours), there were 1 hit, 0 false detections and 0 misses. 1 available position comparison produces an average error of 59 nautical miles.

At the lead time of 3 days (72 hours), there were 1 hit, 0 false detections and 0 misses. 1 available position comparison produces an average error of 48 nautical miles.

At the lead time of 4 days (96 hours), there were 1 hit, 1 false detection and 1 miss. 2 available position comparisons produce an average error of 173 nautical miles.

At the lead time of 5 days (120 hours), there were 1 hit, 2 false detections and 1 miss. 3 available position comparisons produce an average error of 301 nautical miles.

At the lead time of 6 days (144 hours), there were 3 hits, 1 false detection and 0 misses. 4 available position comparisons produce an average error of 288 nautical miles.

At the lead time of 7 days (168 hours), there were 4 hits, 0 false detections and 0 misses. 4 available position comparisons produce an average error of 280 nautical miles.

At the lead time of 8 days (192 hours), there were 3 hits, 1 false detection and 2 misses. 4 available position comparisons produce an average error of 234 nautical miles.

At the lead time of 9 days (216 hours), there were 1 hit, 3 false detections and 3 misses. 3 available position comparisons produce an average error of 272 nautical miles.

At the lead time of 10 days (240 hours), there were 3 hits, 0 false detections and 2 misses. 3 available position comparisons produce an average error of 399 nautical miles.

At the lead time of 11 days (264 hours), there were 2 hits, 0 false detections and 3 misses. 2 available position comparisons produce an average error of 477 nautical miles.

At the lead time of 12 days (288 hours), there were 1 hit, 1 false detection and 4 misses. 2 available position comparisons produce an average error of 645 nautical miles.

At the lead time of 13 days (312 hours), there were 1 hit, 1 false detection and 5 misses. 1 available position comparison produces an average error of 462 nautical miles.

At the lead time of 14 days (336 hours), there were 1 hit, 1 false detection and 4 misses. 1 available position comparison produces an average error of 567 nautical miles.

At the lead time of 15 days (360 hours), there were 1 hit, 1 false detection and 5 misses. 1 available position comparisons produce an average error of 779 nautical miles.

At the lead time of 16 days (384 hours), there were 2 hits, 1 false detection and 3 misses. 2 available position comparisons produce an average error of 1007 nautical miles.

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