Tropical Cyclone Report
Tropical Storm Lester
11 - 13 October 2004
Lester was a short-lived tropical storm
that moved near Acapulco, Mexico.
a. Synoptic History
An area of disturbed weather persisted a
couple hundred nautical miles to the southwest of the Gulf of
Tehuantepec from 8-10 October. On 10 October, a surface low
developed in this area, while the associated deep convection
gradually became organized into slightly curved bands, and initial
Dvorak classifications were performed around 1800 UTC that day. The
gradual development trend continued on the following day, so that
by 1800 UTC 11 October the low-level circulation and cloud pattern
were sufficiently well-organized to indicate the formation of a
tropical depression, centered about 80 n mi south of Puerto
Steered by the flow between a weak
mid-level ridge to its north, and a broad cyclonic circulation to
its southwest, the tropical cyclone moved on a northwestward to
west-northwestward track for a couple of days. A weak upper-level
anticyclone was centered just east of the system, which resulted in
an atmospheric environment that was favorable for intensification.
The depression became Tropical Storm Lester around 1800 UTC 12
October, and the storm reached its peak intensity of 45 kt about
6-12 h later. Radar images indicated that the center passed just to
the south of Acapulco, Mexico around 0400 UTC 13 October. The
interaction with land, and the influence of a larger low-level
cyclonic circulation to the southwest, appeared to have disrupted
the tropical cyclone, and the storm began to weaken rapidly just
after 0600 UTC 13 October. Lester weakened to a tropical depression
with a poorly-defined circulation by 1200 UTC that day, and
observations from an Air Force Reserve Unit Hurricane Hunter
Aircraft flying at an altitude of about 1000 ft indicated that the
system had degenerated into a trough on the northeast side of the
larger low pressure area later that day.
Figure 1 is a "best track" chart of
Lester's path. Wind and pressure histories for this storm are shown
in Figure 2 and Figure 3,
respectively, and the best track positions and
intensities are listed in Table 1.
b. Meteorological Statistics
Observations in Lester (Figure 2 and Figure 3), or
in the post-storm trough, include satellite-based Dvorak technique
intensity estimates from the Tropical Analysis and Forecast Branch
(TAFB), the Satellite Analysis Branch (SAB) and the U. S. Air Force
Weather Agency (AFWA), as well as flight-level observations from a
mission of the 53rd Weather Reconnaissance Squadron of
the U. S. Air Force Reserve Command (the Hurricane Hunters).
Acapulco radar imagery from the National Meteorological Service of
Mexico along with microwave satellite imagery from NOAA
polar-orbiting satellites, the NASA Tropical Rainfall Measuring
Mission (TRMM), the NASA QuikSCAT, and Defense Meteorological
Satellite Program (DMSP) satellites were also useful in tracking
Lester produced locally heavy rainfall,
totaling around 3 to 5 inches, over portions of the coastal areas
of the Mexican states of Oaxaca and Guerrero.
c. Casualty and Damage Statistics
Although Lester very likely produced at
least localized flooding over portions of southern Mexico, no
reports of damages or casualties have been received.
d. Forecast and Warning Critique
Because Lester was so short-lived, there
are few official forecasts to verify, and therefore no meaningful
forecast error statistics. There was a generally leftward bias to
the official track forecasts, and the sudden weakening of Lester
was not anticipated - in fact, the first few NHC intensity
forecasts called for the system to become a hurricane.
The Mexican government issued a tropical
storm watch for the southern coast of Mexico from Punta Maldonado
to Zihuatanejo at 1500 UTC 12 October, and upgraded this watch to a
tropical storm warning for the same area at 2100 UTC 12 October. At
0900 UTC 13 October, the tropical storm warning was extended
westward to Lazaro Cardenas. The entire tropical storm warning was
discontinued at 2100 UTC 13 October.
Table 1: Best track for Tropical Storm
Lester, 11-13 October 2004.
| 11 / 1800|| 14.4|| 96.7|| 1006|| 30|| tropical
| 12 / 0000|| 14.8|| 97.2|| 1006|| 30|| "
| 12 / 0600|| 15.2|| 97.9|| 1006|| 30|| "
| 12 / 1200|| 15.7|| 98.7|| 1006|| 30|| "
| 12 / 1800|| 16.2|| 99.2|| 1004|| 35|| tropical storm
| 13 / 0000|| 16.4|| 99.6|| 1000|| 45|| "
| 13 / 0600|| 16.7|| 100.2|| 1000|| 45|| "
| 13 / 1200|| 16.7|| 100.6|| 1004|| 30|| tropical
| 13 / 1800|| || || || || dissipated
| 13 / 0000|| 16.4|| 99.6|| 1000|| 45|| minimum pressure
Best track positions for
Tropical Storm Lester, 11-13 October 2004.
Selected wind observations and
best track maximum sustained surface wind speed curve for Tropical
Storm Lester, 11-13 October 2004.
Selected pressure observations
and best track minimum central pressure curve for Tropical Storm
Lester, 11-13 October 2004.