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Preliminary Report
Hurricane Cosme
17-22 July 1995

Miles B. Lawrence
National Hurricane Center
1 December 1995


PRELIMINARY REPORTS
Tropical Depression One-E
Hurricane Adolph
Hurricane Barbara
Hurricane Cosme
Tropical Storm Dalila
Tropical Storm Erick
Hurricane Flossie
Tropical Storm Gil
Hurricane Henriette
Hurricane Ismael
Hurricane Juliette


[1995 East Pacific Hurricane Season]

a. Synoptic History

This tropical cyclone can be traced to a cloud cluster that moved across Central America on 10 and 11 July. Moving westward, the cluster showed signs of a low-level circulation by the 15th and it became a depression on the 17th, about 350 n mi south-southeast of the southern tip of Baja California. The track of Cosme begins at this time and is plotted in Fig. 1 (38K GIF). Table 1 is a listing, every six hours, of position, maximum one-minute surface wind speed, and minimum central sea level pressure.

Movement was slow and toward the northwest from the 17th to the 20th, while the depression gradually strengthened to a 65-knot hurricane. Cosme then turned and moved a little faster toward the west-southwest and weakened. By the 22nd, only a swirl of low clouds remained, about 850 n mi west-southwest of the southern tip of Baja California.


b. Meteorological Statistics

Figures 2 (24K GIF) and 3 (26K GIF) show the curves of minimum sea-level pressure and maximum one-minute wind speed as a function of time, along with the data on which they are based. All of the data in both figures are estimates from satellite imagery using the Dvorak method.

A ship was located about 60 n mi east of the center of Cosme at 1800 UTC on the 18th and reported a sustained wind speed of 15 knots and 1006.1-mb pressure. At this time, satellite-based wind speed estimates from both the Tropical Analysis and Forecast Branch and from the Satellite Analysis Branch were 45 kts. One might normally expect 35-knot winds to extend out to 60 n mi from the center of a tropical storm, unless it tiny. Cosme was not tiny.

This suggests considerable uncertainty in the determination of the maximum sustained wind in a tropical cyclone.


c. Casualty and Damage Statistics

Cosme did not affect land and there are no casualties or damage.


d. Forecast and Warning Critique

Average track forecast errors for Cosme range from 84 n mi at 24 hours to 188 n mi at 48 hours to 319 n mi at 72 hours. These errors are somewhat higher than the long-term errors for the eastern Pacific basin and were influenced by the turn on the 20th from northwestward to west-southwestward. Even after the turn occurred, the track guidance based on the steering from the Aviation global/spectral model insisted on a northwestward motion. The simple climatology-persistence model had smaller track errors than all of the guidance models and the official forecast.


 
Table 1. Track of Hurricane Cosme, 17 - 22 July 1995.
Date/Time
(UTC)
Position Pressure
(mb)
Wind Speed
(kt)
Stage
Lat. (°N)Lon. (°W)
17/000017.0108.1100725 Trop. Dep.
060017.2108.4100730"
120017.3109.0100630"
180017.5109.5100530"
18/000017.8109.8100430"
060018.1110.5100235Trop. Storm
120018.4111.2100040"
180018.8112.099750"
19/000019.3112.899555"
060019.7113.699355"
120020.2114.499060"
180020.8115.498765Hurricane
20/000021.5116.598565"
060021.7117.398565"
120021.8118.398760Trop. Storm
180021.6119.499150"
21/000021.4120.699640"
060021.2121.7100235"
120021.0122.8100530Trop. Dep.
180020.8124.0100825"
22/000020.6125.0100925"
0600     dissipated
 
20/000021.5116.598565 minimum pressure



Brian Maher
Jack Beven

Last updated January 2, 1999