30 June 2002
Track Forecast Errors
Two tropical storms, Rammasun and Chatann finally formed over the western North Pacific. The forecasts from various models of Rammasun differ quite a bit, not so much in the direction but in the speed. While ECMWF forecasts landfall over Taiwan at around 05 Jul 12 UTC (hereafter 0512) (Fig. 1), UK Met Office predicts that by 0400, Rammasun will already be to the north of Taiwan (Table 1). NOGAPS' prediction is even slower and further east. By 0500, Rammasun is predicted to be east of Taiwan (Fig. 2). So how would a consensus forecast be in this case?
Also, the 168-h ECMWF forecast valid for 0212 differs significantly from the 72-h valid at the same time in terms of speed (Figs. 3 and 4). It would be interesting to see which one turns out to be correct and then try to guess why.
TROPICAL STORM RAMMASUN ANALYSED POSITION : 12.1N 135.6E
VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 30.06.2002 12.1N 135.6E STRONG
12UTC 30.06.2002 13.7N 134.8E STRONG INTENSIFYING SLIGHTLY
00UTC 01.07.2002 15.5N 133.1E STRONG INTENSIFYING RAPIDLY
12UTC 01.07.2002 17.1N 131.0E STRONG INTENSIFYING SLIGHTLY
00UTC 02.07.2002 19.4N 128.5E STRONG WEAKENING SLIGHTLY
12UTC 02.07.2002 19.7N 126.6E INTENSE INTENSIFYING SLIGHTLY
00UTC 03.07.2002 21.1N 124.5E INTENSE INTENSIFYING SLIGHTLY
12UTC 03.07.2002 24.9N 122.0E INTENSE LITTLE CHANGE
00UTC 04.07.2002 26.2N 121.5E INTENSE LITTLE CHANGE
12UTC 04.07.2002 28.9N 120.9E INTENSE WEAKENING RAPIDLY
00UTC 05.07.2002 31.7N 122.0E STRONG LITTLE CHANGE
12UTC 05.07.2002 34.4N 123.0E STRONG INTENSIFYING SLIGHTLY
00UTC 06.07.2002 36.2N 124.3E STRONG INTENSIFYING SLIGHTLY
Fig. 2.
