Fact Sheet United States Air Force Reserve

Weather Reconnaissance Glossary

ARWO. Aerial Reconnaissance Weather Officer. The flight meteorologist.

CARCAH. Chief, Aerial Reconnaissance Coordination, All Hurricanes. The 53rd's liaison at the National Hurricane Center. They coordinate the requirements for

Cyclone. A low pressure system, in which the winds circulate counter-clockwise in the Northern Hemisphere. See also tropical cyclone.

Eye. The relatively calm center of the tropical cyclone that is more than one half surrounded by wall cloud.

Eye Wall. An organized band of cumuliform clouds (thunderstorms) immediately surrounding the center of a tropical cyclone. Also called wall cloud, not to be confused with the "wall cloud" associated with a tornado.

Fix. See Vortex Fix.

Hurricane Season. The portion of the year having a high incidence of hurricanes. The seasons for specific areas are:

Atlantic, Caribbean, Gulf of Mexico, Central Pacific: June 1 to November 30

Eastern Pacific: May 15 to November 30

Hurricane Watch. An announcement for specific coastal areas that a hurricane or an incipient hurricane condition poses a possible threat, generally within 36 hours.

Hurricane Warning. A warning that sustained winds of 64 knots (74 miles per hour) 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.

Knot. A measurement of speed. It is slightly faster than a mile per hour. To convert, 1 knot = 1.152 mph = 0.515 m/s = 1.85 km/hr.

Low-level Invest. An investigative mission is tasked on tropical disturbances to determine the existence or non-existence of a "closed circulation" (winds blowing in a complete circle), supply weather observations in required areas, and determine the vortex center, if any. These missions are flown at 500 to 1500 feet.

Saffir-Simpson Hurricane Scale. A scale ranging from one to five based on the hurricane's present intensity. This can be used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane. In practice, sustained surface wind speed (1-minute average) is the parameter which determines the category since storm surge is strongly dependent on the slope of the continental shelf.

CATEGORY ONE. Winds 74-95 mph (63-82 kts). No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Also, some coastal flooding and minor pier damage.

CATEGORY TWO. Winds 96-110 mph (83-95 kts). Some roofing material, door, and window damage of buildings. Considerable damage to vegetation and mobile homes. Flooding damages piers, and small craft in unprotected anchorages break moorings. Evacuation of some shoreline residences and low-lying island areas is required.

CATEGORY THREE. Winds 111-130 mph (96-113 kts). Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger sturctures damaged by floating debris. Low lying escape routes inland are cut by rising water 3 to 5 hours before the storm center arrives.

CATEGORY FOUR. Winds 131-155 mph (114-135 kts). More extensive curtainwall failures with some complete failure of roof systems on many small residences. Major erosion of beach areas. Terrain may be flooded well inland.

CATEGORY FIVE. Winds greater than 155 mph (135 kts). Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Flooding causes major damage to lower floors of all structures near the shoreline. Massive evacuations of residential areas may be required.

Note: A "major" hurricane is one that is classified as a Category 3 or higher.

Storm Surge. 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 tide from the observed storm tide. Note: waves on top of the storm surge will create an even greater high-water mark.

Storm Tide. The actual level of sea water resulting from the astronomic tide combined with the storm surge. If the storm comes ashore during astronomical low tide, the surge will be decreased by the amount of the low tide. If the storm makes landfall during astronomical high tide, the surge will be that much higher.

Synoptic Surveillance. "Synoptic" is a meteorological term which covers the largest weather systems (such as hurricanes and high pressure systems). "Synoptic Surveillance" is a weather reconnaissance mission flown to provide vital meteorological information in data sparse ocean areas as a supplement to existing surface, radar, and satellite data. Synoptic flights better define the upper atmosphere and aid in the prediction of tropical cyclone motion and intensity.

Tropical Classifications:

Tropical Disturbance. A discrete tropical weather system of apparently organized convection--generally 100 to 300 miles 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. In other words, a blob of thunderstorms. The Hurricane Hunters may fly a "low-level investigative mission" on a tropical disturbance to see if the winds are forming a "closed circulation", which means it is reaching the next stage of development, the tropical depression.

Tropical Cyclone. A warm-core, non-frontal low pressure system of synoptic scale that develops over tropical or subtropical waters and has a definite organized surface circulation. This is a generic term which covers tropical depressions, tropical storms, and hurricanes.

• Tropical Depression, or "TD". A tropical cyclone in which the maximum sustained surface wind speed is 33 knots (38 mph) or less. At this point, it gets a cyclone number, starting with "TD01" at the beginning of each storm season.

• Tropical Storm. A tropical cyclone in which the maximum sustained surface wind speed (1 minute mean) ranges from 34 knots (39 mph) to 63 knots (73 mph). At this point, the cyclone gets a name. In the Atlantic/Caribbean/Gulf of Mexico basin, the names start with "A" each season.

  The names for 1997 in the Atlantic/Caribbean/Gulf of Mexico:

  Ana Bill Claudette Danny Erika Fabian Grace Henri Isabel Juan Kate Larry Mindy Nicholas Odette Peter Rose Sam Teresa Victor Wanda

• Hurricane/Typhoon. A warm-core tropical cyclone in which the maximum sustained surface wind is 64 knots (74 mph) or more. A "typhoon" is a hurricane on the other side of the International Dateline.

Vortex Fix. The location of the surface and/or flight level center of a tropical or subtropical cyclone obtained by reconnaissance aircraft penetration.

(CURRENT AS OF APRIL 1997)