Hurricane Jimena was characterized not only by its
exceptionally rapid intensification but also by its sudden
and accelerated decay.
a. Synoptic History
Jimena developed from a large area of disturbed weather
centered in the vicinity of 10°N 130°W, where the sea surface
temperatures were 1.0 or 1.5 degrees above normal. This system was
probably related to a tropical wave which moved slowly
westward for several days across the eastern North Pacific. Initially, the
disturbance was under an unfavorable upper-level
westerly wind environment. The convection increased and an upper-level
anticyclone gradually built over the system. A tropical depression
formed near 10.9°N 133.1°W at 1200 UTC 25 August. After becoming
a tropical storm by 0000 UTC 26 August, Jimena intensified rapidly.
It quickly developed an eye and the Dvorak
T-numbers increased substantially. In fact, the estimated winds increased from
65 knots to 115 knots
in about 12 to 15 hours. Jimena's winds were 115 knots for a
couple of days and peaked at 120 knots at
1500 UTC 28 August. The objective T-numbers near that time were
oscillating around 6.5 on the Dvorak scale. Jimena was moving on a
north- northwesterly track when a strong upper-level trough moved
by and sheared the hurricane.
Jimena weakened as fast as it developed. Wind estimates decreased from
115 to 30 knots in
about 24 hours.
The remaining low-level circulation
center moved westward
across 140°W and entered the
Hurricane Center (CPHC) area of responsibility just after 1200 UTC on the 29th. It
weakened further and was declared dissipated by 0000 UTC 30 August.
Jimena's track is shown in Fig. 1 (9K GIF).
Table 1 is a listing, at six-hourly intervals,
of the best-track position, estimated minimum
central pressure and maximum 1-minute surface wind speed.
b. Meteorological Statistics
The best track pressure and wind curves as a function of time
are shown in Figs. 2 (8K GIF) and
3 (8K GIF) and are based on satellite intensity
estimates from the Tropical Analysis and Forecast Branch (TAFB),
the Satellite Analysis Branch
(SAB) and the Air Force Global
Weather Center (AFGWC). The estimated central pressure of Jimena
dropped at a rate of 3.5 mb an hour during its rapid
intensification phase from 0000 to 1200 UTC 27 August.
c. Casualty and Damage Statistics
There are no reports of casualties or damage associated with
d. Forecast and Warning Critique
The average official forecast error (11 forecasts) at 24 hours
was 101 n mi and reached 456 n mi at 72 hours (3 forecasts). These
numbers are much larger than the long-term (1988-1995) average
errors of 71 and 196 n mi, respectively.
None of the official forecasts captured either the rapid
intensification nor the rapid decay.