Hurricane / Typhoon:
A warm-core tropical cyclone in which the maximum sustained surface wind (using the U.S. 1-minute average) is 64 kt (74 mph or 119 kph) or more, and blowing counterclockwise (Northern Hemisphere) around a calm center of low pressure.. The term hurricane is used for Northern Hemisphere cyclones east of the International Dateline to the Greenwich Meridian. The term typhoon is used for Pacific cyclones north of the Equator west of the International Dateline.
Wind gusts may exceed the sustained winds by 25 to 50 percent. Hurricanes are rated by their wind speed, with a Category 1 being the weakest hurricane at 64 - 82 Kts (74 - 95 mph) and Category 5 being the most intense at over 135 Kts (over 155 mph). Hurricanes also can generate tornadoes of 130 - 260 Kts (150 - 300 mph).
A warning means that a hurricane is expected to strike within 24 hours. Residents must be ready to leave if local officials order an evacuation of their area.
A warning that sustained winds 64 kt (74 mph or 119 kph) or higher associated with a hurricane are expected in a specified coastal area in 24 hours or less. A hurricane warning can remain in effect when dangerously high water
or a combination of dangerously high water
and exceptionally high waves continue, even though winds may be less than hurricane force.
An announcement of specific coastal areas that a hurricane or an incipient hurricane condition poses a possible threat, generally within 36 hours.
When a watch is declared, hurricane conditions are possible and may threaten an area within 36 hours, and the area affected and danger
period will be specified. Voluntary evacuations may be encouraged at this stage.
An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide.
It can be devastating and in fact is a major cause of damage from hurricanes. The storm surge itself is caused by the wind and pressure "pushing" the water into the continental shelf and onto the coastline. The height of a surge is basically measured as a deviation from the mean sea level in the area, and in some historical storms, this value has reached over 20 feet.
The actual level of sea water resulting from the astronomic tide combined with the storm surge.
A tropical cyclone (low-pressure front with a rotary circulation of clouds) in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 33 kt (38 mph or 62 kph) or less.
A large area of rain and clouds with no circulating winds. A discrete tropical weather system of apparently organized convection - generally 100 to 300 nmi in diameter - originating in the tropics or subtropics, having a nonfrontal migratory character, and maintaining its identity for 24 hours or more. It may or may not be associated with a detectable perturbation of the wind field.
A storm with a distinct rotation of winds around a center of low pressure with a barometric reading of 29.4 inches or lower. When sustained winds reach 34 Kts (39 mph) or higher, the storm is given a name by the National Hurricane Center in Miami.
Rainfall may equal or exceed that of some hurricanes, and tides may be several feet higher than normal. Wind gusts may reach hurricane velocity of 64 Kts (74 mph) or more and, depending on tides and other conditions, damage may be just as severe as that caused by a hurricane.
A warm-core, nonfrontal low pressure system of synoptic scale that develops over tropical or subtropical waters and has a definite organized surface circulation.
A weak, low-pressure front (trough or cyclonic curvature maximum) moving westward in the trade
winds (easterlies). Clouds and rain are linked to the wave, but it has no wind circulation. May be short-lived or move up to 3,000 miles without change. The wave may reach maximum amplitude in the lower middle troposphere.
Official information issued by tropical cyclone warning centers describing all tropical cyclone watches and warnings in effect along with details concerning tropical cyclone locations, intensity and movement, and precautions that should be taken.
A subjectively smoothed path, versus a precise and very erratic fix-to-fix path, used to represent tropical cyclone movement. It is based on an assessment of all available data.
The vertical axis or core
of a tropical cyclone. It is usually determined by cloud vorticity patterns, wind, and/or pressure distributions.
The location of the center of a tropical or subtropical cyclone obtained by reconnaissance aircraft penetration, satellite, radar
, or synoptic data.
The relatively calm center of the tropical cyclone that is more than one half surrounded by wall cloud.
Eye Wall/Wall Cloud:
An organized band of cumuliform clouds immediately surrounding the center of a tropical cyclone. Eye wall and wall cloud are used synonymously.
The best estimate of the movement of the center of a tropical cyclone at a given time and given position. This estimate does not reflect the short-period, small scale oscillations of the cyclone center.
A warning of 1-minute sustained surface winds in the range 34 kt (39 mph or 63 kph) to 47 kt (54 mph or 87 kph) inclusive, either predicted or occurring not directly associated with tropical cyclones.
High Wind Warning:
A high wind warning is defined as 1-minute average surface winds of 35 kt (40 mph or 64 kph) or greater lasting for 1 hour or longer, or winds gusting to 50 kt (58 mph or 93 kph) or greater regardless of duration that are either expected or observed over land.
The portion of the year having a relatively high incidence of hurricanes.
The hurricane season in the Atlantic, Caribbean, and Gulf of Mexico
runs from June 1 to November 30.
The hurricane season in the Eastern Pacific basin runs from May 15 to November 30. The hurricane season in the Central Pacific basin runs from June 1 to November 30.
Best regards for the 2005 season.