a. Synoptic History
Marty's origins could be associated with two westward-traveling
tropical waves,
one which crossed Central America around the end of August, and another which
entered the eastern Pacific about three days later.
These two waves appeared to contribute to an area of disturbed weather which was
located in the vicinity of 129°W early on 10 September. Meteorologists at the
Tropical Prediction Center's Tropical Analysis and Forecast Branch
(TAFB) began to locate and "classify" the disturbance
on that date. Deep convection associated with the system increased in a
"bursting"-type event on the 11th, but there was no significant increase in organization
until the following day, when curved cloud bands became readily apparent. The
system is estimated to have become Tropical Depression
Fifteen-E at 1800 UTC 12 September, at which time Dvorak T-numbers
were up to T2.0 from both TAFB and the
Synoptic Analysis Branch (SAB).
The depression was centered about 1300 n mi east-southeast of the island of Hawaii at that time.
Figure 1 (12K GIF) shows the best track
and Table 1 lists the positions and intensities every six
hours.
Steering currents in the vicinity of this
tropical cyclone remained fairly weak, and
the system never moved faster than 5 or 6 knots throughout its lifetime. The
depression moved a little south of due westward on the 12th and 13th, and, after
strengthening into Tropical Storm Marty around
0000 UTC on the 14th, it turned southwestward and then southward. Marty's forward
speed slowed to a crawl on the 15th, and it weakened back to a depression that day.
The weakening was apparently caused by vertical shear due to upper-level southeasterly
flow over the area, with the low-cloud center becoming
clearly exposed. Strong shearing continued, weakening the slow-moving Marty to dissipation
around 1800 UTC 16 September.
b. Meteorological Statistics
Figures 2 (13K GIF)
and 3 (13K GIF) depict the curves of minimum central
sea-level pressure and maximum one-minute average "surface" (10 meters above ground
level) wind speed, respectively, as a function of time for
Tropical Storm Marty. Also plotted are the observations on which the curves are based,
consisting of Dvorak-technique estimates (from the TAFB, the SAB, and the U.S.
Air Force Global Weather Center
[AFGWC]) using geostationary and polar-orbiting satellite imagery.
c. Casualty and Damage Statistics
No reports of casualties or damage due to Marty have been received at the National
Hurricane Center and, since the storm remained at sea, nothing was likely damaged and
probably no one was hurt.
d. Forecast and Warning Critique
Marty was a tropical storm for only about 30 hours. Therefore, no meaningful
forecast statistics are available. However, the official forecasts never called for the
cyclone to move very fast or to strengthen much. This turned
out to be generally correct.
Marty did not threaten land, and watches and/or warnings were not required.
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