XXIV. NS MOBILE, ALABAMA
SUMMARYThe hurricane season poses a serious threat to Naval Station Mobile. During the 107-year period from 1886-1992, an average of one tropical cyclone or hurricane has passed within 180 nmi of Mobile each year. Several storms of record have produced sustained winds in excess of 40 kt with gusts commonly exceeding 60 kt. Dauphin Island reported gusts to 126 kt during Hurricane Frederic in 1979. The area is susceptible to storm surge, with water elevations over 7 ft above mean sea level being recorded at least three times during the period of 1806-1969. Hurricane Frederic generated a 12 ft storm surge in 1979.
The hurricane season for Mobile is from late May through early November, with September being the major threat month. The principal threat is from tropical cyclones approaching from the southwest, south and southeast. When storms of record were at their closest point of approach (CPA) to Mobile, their average monthly direction of movement varied from 339° to 027°, with the overall average direction of movement being 006°.
Mobile is not a hurricane haven. Early threat assessment is essential; limited evasion options dictate that any sortie be initiated soon after Hurricane Condition III is set. Evasion rationale is based on: the susceptibility of the Mobile Bay area to storm surge that could inundate the Naval Station, the absence of sheltered anchorages, the aspect of narrow channels cut through shallow bay waters that would be vulnerable to blockage if a ship should sink during a storm, and the always present danger of damage from other vessels that may break loose from their moorings in the Port of Mobile and other locations on Mobile Bay during strong winds.
Advice for shallow draft vessels is to remove them from the water and transport them to higher ground away from the Naval Station. If that is not feasible, limited shelter may be available in the Mobile River above Mobile.
The Port of Acapulco is considered to be a protected harbor for the purpose of avoiding or reducing the effects of a passing tropical cyclone. Historically, hurricanes have had little impact on the Port based on their tracks, their strength, the topography of the Port, and refractive effects on lessening wave action on the north side of Acapulco Bay. Additionally, storms originate normally within 72 hours of CPA south of the Port, and that allows very little time and margin of safety to depart from the Port, cross the T, and maneuver to evade northwesterly heading tropical cyclones.