Tropical Cyclone Report
Tropical Storm Cosme
13 - 15 July 2001
James L. Franklin
National Hurricane Center
18 July 2001
Cosme was a weak and short-lived tropical storm that did not
a. Synoptic History
Cosme developed from a tropical wave that crossed Central
America and emerged into the eastern Pacific basin on 6 July.
Hovmoller diagrams of the tropical Atlantic prior to the
6th are not conclusive, but indicate that the
responsible system emerged from the African coast on either the
24th or 27th of June.
The wave moved slowly westward from 6-10 July. On the
10th, the convective pattern began to show signs of
organization about 350 n mi south of Acapulco, Mexico, and the
system received its first Dvorak satellite classification. Over the
next two days, the system moved generally west-northwestward as
multiple low-level circulations developed within a broad area of
low pressure. During this period, development of the disturbance
was hindered by southerly shear from an upper-level trough to the
west of the disturbance that caused the system to become elongated
north-south. On the 12th, the upper trough cut off
southwest of the disturbance and the organization improved. By
early on the 13th, a single low-level circulation center
had become established and it is estimated that a tropical
depression formed at 0600 UTC about 330 n mi southwest of
The "best track" chart of the tropical cyclone's path is given
in Figure 1, with the wind and pressure histories shown in
Figure 2 and Figure 3, respectively.
The best track positions and intensities are
listed in Table 1.
The depression moved west-northwestward at about
15 kt and quickly reached tropical storm strength by 1200 UTC on
the 13th, about 425 n mi south of Cabo San Lucas,
Mexico. The forward motion then slowed to about 10 kt over the next
12 hours. Cosme's development was hindered by easterly shear; its
peak intensity of 40 kt was reached late on the 13th. By
early on the 14th convection was limited and well
removed from the center. Cosme weakened back to a tropical
depression by 1800 UTC, when it was about 400 n mi southwest of
Cabo San Lucas. Cosme produced no more significant convection after
about 0600 UTC on the 15th, at which point the tropical
cyclone became a non-convective low center. The low then moved
slowly westward until it dissipated on the 18th about
820 n mi west-southwest of Cabo San Lucas.
b. Meteorological Statistics
Observations in Cosme (Figure 2 and Figure 3)
are limited to
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). The peak intensity of 40 kt is a compromise between
estimates from SAB and TAFB.
c. Casualty and Damage Statistics
There were no reports of damage or casualties associated with
d. Forecast and Warning Critique
Cosme was a tropical storm for roughly 30 h, too short a time
for a meaningful forecast evaluation. After Cosme became a tropical
storm, initial intensity forecasts (and the SHIPS model guidance)
overestimated its development potential.
There were no watches and warnings associated with Cosme.
Table 1: Table 1. Best track for Tropical Storm Cosme, 13-15 July
|Lat. (°N)||Lon. (°W)
|13 / 0600||15.0||108.4||1007||25||tropical depression
|13 / 1200||15.8||110.0||1003||35||tropical storm
|13 / 1800||16.3||111.4||1000||40||"
|14 / 0000||16.8||112.4||1000||40||"
|14 / 0600||17.2||113.3||1002||35||"
|14 / 1200||17.7||114.2||1003||35||"
|14 / 1800||18.2||115.1||1004||30||tropical depression
|15 / 0000||18.8||115.9||1005||25||"
|15 / 0600||19.2||116.6||1006||25||"
|15 / 1200||dissipated to low
|13 / 1800||16.3||111.4||1000||40||minimum pressure
Best track positions for Tropical Storm Cosme, 13-15 July 2001.
Best track maximum sustained surface wind speed curve for Tropical Storm
Cosme, 13-15 July 2001, and the observations on which the best
track curve is based.
minimum central pressure curve for Tropical Storm Cosme, 13-15 July
2001, and the observations on which the best track curve is