Genevieve was a weak tropical cyclone
that meandered over the eastern North Pacific
for over 11 days without affecting any land areas.
a. Synoptic History
Satellite imagery showed an increase in cloudiness and thunderstorms in the vicinity
of the Gulf of Tehuantepec on 23 September. The tropical disturbance
moved westward over the next few days without signs of development. Deep convection
became more concentrated and the "best track"
indicates that a tropical depression
formed from the disturbance near 1800 UTC 27 September, while centered about 400
n mi south of the southern tip of Baja California (Fig. 1
[27K GIF] and Table 1). The developing
cyclone initially moved westward near 10 knots.
The tropical depression quickly strengthened into
Tropical Storm
Genevieve as upper-level outflow became better established and convective banding increased.
Maximum winds of 45 knots are estimated to have occurred from late on
the 28th to early on the 30th.
Genevieve tracked toward the west-southwest and decelerated. As steering currents
collapsed, the forward motion slowed to less than 5 knots by 30 September. A rather
erratic motion occurred between 30 September and 8 October, during which time the
center
of Genevieve moved less than 200 n mi. Although there is uncertainty in the
precise track, visible satellite fixes indicate that the
tropical cyclone executed two loops during this time.
Genevieve weakened to a tropical depression near 0000 UTC 1 October in response
to increased easterly shear. The shear temporarily diminished on 6 October, and
Genevieve regained tropical storm strength for about 36 hours. Thereafter, the tropical
cyclone again weakened to a tropical depression as it entrained drier air.
Genevieve dissipated on 9 October less than 650 n mi from where it developed a little
over 11 days earlier, although occasional flare-ups of convection occurred in
association with a low-level swirl for a few more days.
b. Meteorological Statistics
Figures 2 (23K GIF) and
3 (24K GIF) show "best track"
curves of minimum central pressure and maximum one-minute surface wind speed,
respectively, as a function of time. The observations on which the curves
are based are also plotted and consist of Dvorak-technique estimates
using satellite imagery. The NEDLLOYD DEJIMA reported a north wind
of 35 knots at 1800 UTC 7 October while located about 200 n mi to the north-northwest
of the center of Genevieve.
This was the only ship report of tropical storm force winds received.
c. Casualty and Damage Statistics
No reports of casualties or damage associated with Genevieve have been received at
the NHC.
d. Forecast and Warning Critique
Genevieve was categorized as a tropical storm for only four days. Those days were not
consecutive, so only limited forecast evaluations are possible. During Genevieve's life
as a tropical storm, the average official track forecast errors ranged from 145 n mi at
24 hours (11 cases) to 283 n mi at 48 hours (4 cases). These errors are nearly double
the previous eight year averages. The official forecasts as well as many of the track
prediction models consistently indicated a west-northwestward motion which did not occur.
The intensity forecasts showed a positive bias (i.e., intensity was overestimated). This
bias resulted primarily from the early forecasts that, incorrectly, expected Genevieve
to remain within a light-shear environment and strengthen.
Operationally, advisories were discontinued at 2100 UTC 3 October when the cloud
pattern appeared very disorganized; advisories resumed at 2100 UTC 6 October. In
contrast, a post-analysis indicates that a weak low-level circulation persisted and the
best track shows depression status through this period.
The tropical storm did not threaten land. Therefore, coastal watches or warnings were
not necessary.
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