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Preliminary Report
Tropical Storm Hermine
17-20 September 1998

Lixion A. Avila
National Hurricane Center
9 November 1998

Tropical Storm Alex
Hurricane Bonnie
Tropical Storm Charley
Hurricane Danielle
Hurricane Earl
Tropical Storm Frances
Hurricane Georges
Tropical Storm Hermine
Hurricane Ivan
Hurricane Jeanne
Hurricane Karl
Hurricane Lisa
Hurricane Mitch
Hurricane Nicole

[1998 Atlantic Hurricane Season]

a. Synoptic History

Hermine developed from a tropical wave which crossed Dakar, Senegal on 5 September and moved westward across the Atlantic. The wave was void of significant thunderstorm activity until it reached the Windward Islands where cloudiness and showers increased and there was a large 24-h pressure change on 12 September. The wave continued westward very close to the South American coast and then moved northwestward through the Northwest Caribbean Sea and the Yucatan Channel where a low pressure system developed. The system began to interact with an upper low in the Gulf of Mexico and another tropical wave which reached the area. During this period, a large and well-defined monsoon-type flow prevailed over Central America, the Northwestern Caribbean Sea and the Gulf of Mexico. It was not until 1200 UTC 17 September that the system acquired enough organization to be classified as a tropical depression.

The depression made a cyclonic loop over the central Gulf of Mexico while interacting with the upper-low located in the Bay of Campeche. The depression gradually became organized despite the unfavorable upper-level wind shear which prevailed in the area and reached tropical storm status at 1200 UTC 19 September. Hermine moved on a general northward track and made landfall as a weakening 35-knot tropical storm near Cocodrie, Louisiana at 0500 UTC 20 September.

Hermine's track is shown in Fig. 1 (15K GIF). Table 1 is a listing, at six-hourly intervals, of the best-track position, estimated minimum central pressure and maximum 1-minute surface wind speed.

b. Meteorological Statistics

The best track pressure and wind curves as a function of time are shown in Figs. 2 (15K GIF) and 3 (14K GIF) and are primarily based on data from reconnaissance flights, WSR-88D data, surface observations and satellite intensity estimates from the Tropical Analysis and Forecast Branch (TAFB), the Satellite Analysis Branch (SAB) and the Air Force Weather Agency, (AFGWC in figures). Hermine produced rains of about .5 to 1 inches and there were no reports of tropical storm force winds near the area of landfall.

c. Casualty and Damage Statistics

There are no reports of casualty and damage from Hermine.

d. Forecast and Warning Critique

Due to the uncertainties in the forecast while the tropical cyclone was looping in the central Gulf of Mexico, it was necessary to issue tropical storm watches and warnings for a large portion of the Gulf coast. Tropical storm watches and warnings are summarized in Table 2.

Hermine was a tropical storm for about 24 hours. Therefore, the evaluation of the average forecast errors would not be meaningful.

Table 1. Best track, Tropical Storm Hermine, 17- 20 September, 1998
Position Pressure
Wind Speed
Lat. (°N)Lon. (°W)
17/120026.990.3100130tropical depression
060025.792.5 99930"
120026.092.5 99930"
180025.992.3100030 "
120027.591.3100135tropical storm
120030.590.5100230tropical depression
20/000029.090.999940maximum intensity
20/050029.190.9100035Landfall near Cocodrie LA

Table 3. Watch and warning summary, Hurricane Earl, September 1998.
17/2100 Tropical Storm watch issued Sargent, Texas to Grand Isle, Louisiana
18/0900 Tropical Storm watch extended southward From Sargent, to Matagorda, Texas
18/1500 Tropical Storm watch extended eastward to Pascagoula Mississippi
19/0300 Tropical Storm watch discontinued west of High island, Texas.
19/1500 Tropical Storm warning issued from Morgan City, Louisiana eastward to Pensacola Florida
Tropical Storm watch discontinued from east of Pensacola to Destin, Florida
Tropical Storm watch discontinued west of Sabine Pass, Texas
19/2100 Tropical Storm warning extended westward from west of Morgan City to Intracoastal City, Louisiana
20/0300 tropical Storm watch discontinued west of Intracoastal City
20/1200 tropical storm warning and watch discontinued all areas

Jack Beven

Last updated April 30, 1999