Gilma was a category 1 hurricane (on the Saffir-Simpson Hurricane Scale) that took a climatological west-northwesterly track over the open waters of the eastern North Pacific.
a. Synoptic History
The precursor disturbance for Hurricane Gilma was a tropical wave that moved off the coast of Africa on 20-21 July. The wave quickly lost convection which it did not regain until it entered the eastern Caribbean on the 28th. The wave moved into the eastern Pacific on 2 August. Early on the 4th a cloud system center became briefly trackable about 300 n mi south of Zihuatanejo, Mexico. This center dissipated but a second one consolidated rapidly late in the day and a tropical depression formed on the 5th at 0000 UTC, about 250 n mi south of Manzanillo. 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 is listed in Table 1.
The depression remained very poorly organized for the next 36 hours and did not have a very well-defined circulation center while it moved to the west-northwest, a heading from which the cyclone never deviated very much. By 1200 UTC on the 5th, the cloud pattern had become better organized and the cyclone became a tropical storm about 350 n mi south of Cabo San Lucas. Gilma gradually intensified over the next couple of days and became a hurricane at 0600 UTC on the 8th about 500 n mi west-southwest of Cabo San Lucas. Gilma's peak intensity of 70 kt was reached at 1200 UTC on the 8th as water temperatures under the cyclone's center fell below about 26C. A smooth decline in intensity ensued over the next 60 hours, with the system weakening to a tropical depression at 0000 UTC on the 10th. No significant convection was noted after about 1800 UTC on the 10th, and the tropical cyclone had dissipated by 0000 UTC on the 11th about 750 n mi west of Cabo San Lucas.
Meteorological Statistics
Observations in Gilma (Figure 2 and Figure 3) were 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). Of note is the relatively large discrepancy between intensity estimates from the various agencies on the 7th and 8th, which introduces more than the usual uncertainty regarding the peak intensity attained by the cyclone.
There were no ship reports of winds of tropical storm force associated with Gilma.
Casualty and Damage Statistics
There were no reports of damage or casualties associated with Gilma.
Forecast and Warning Critique
There were relatively few verifying forecasts for Gilma (twelve at 12 hours and only two at 72 hours). Average official track errors for Gilma were 27, 49, 61, 82, and 93 n mi for the 12, 24, 36, 48, and 72 h forecasts, respectively. These errors are lower than the average official track errors for the 10-yr period 1990-1999 (37, 69, 101, 132, and 189 n mi, respectively). Intensity errors were close to or less than the long term averages.
There were no watches or warnings associated with Gilma.
Table 1. Best track for Hurricane Gilma, 5-11 August 2000. Date/Time
(UTC)Position Pressure
(mb)Wind Speed
(kt)Stage Lat. (°N) Lon. (°W) 05 / 0000 15.0 105.2 1005 30 tropical depression 05 / 0600 15.2 106.1 1005 30 " 05 / 1200 15.5 106.9 1005 30 " 05 / 1800 15.8 107.8 1005 30 " 06 / 0000 16.2 108.8 1005 30 " 06 / 0600 16.6 109.9 1005 30 " 06 / 1200 17.0 111.0 1003 35 tropical storm 06 / 1800 17.4 112.0 1000 45 " 07 / 0000 17.9 113.0 995 50 " 07 / 0600 18.2 114.1 993 55 " 07 / 1200 18.4 114.9 991 60 " 07 / 1800 18.5 115.8 991 60 " 08 / 0000 18.7 116.7 990 60 " 08 / 0600 18.9 117.5 987 65 hurricane 08 / 1200 19.0 118.3 984 70 " 08 / 1800 19.3 119.1 986 65 " 09 / 0000 19.8 119.7 989 60 tropical storm 09 / 0600 20.2 120.2 992 55 " 09 / 1200 20.7 120.6 996 45 " 09 / 1800 21.2 121.1 999 35 " 10 / 0000 21.7 121.6 1002 30 tropical depression 10 / 0600 22.0 122.2 1004 30 " 10 / 1200 22.1 122.7 1005 25 " 10 / 1800 22.2 123.2 1006 25 " 11 / 0000 22.3 123.6 1007 25 " 11 / 0600 dissipated 08 / 1200 19.0 118.3 984 70 minimum pressure
Figure 1. Best track positions for Hurricane Gilma, 5-11 August 2000.
Figure 2. Best track maximum sustained surface wind speed curve for Hurricane Gilma, 5-11 August 2000, and the observations on which the best track curve is based.
Figure 3. Best track minimum central pressure curve for Hurricane Gilma, 5-11 August 2000, and the observations on which the best track curve is based.
