Storms & Hurricanes

Weather cannot be controlled but understanding it can make operations safe and successful. Weather predictions can be made by observing your surroundings. Clouds that are high, are good indications of fair weather. Clouds that are low to the earth indicate a possibility of rain. A ring around the moon, or sun, also indicates rain. The ring is created by ice in the clouds, which scatter the light. Low clouds over mountains mean a weather change. When clouds increase, foul weather is on the way. When they diminish, dry weather is on the way.

Storms are year round and to keep abreast of the situation the team should have a National Oceanic and Atmospheric Administration (NOAA) weather radio. These radios are economical and portable. With the weather radio the team can get up to the minute information at the touch of a button. NOAA broadcast regular forecast and special warnings 24 hours a day.

Old sayings still have credibility. "The farther the sight, the nearer the rain" means that if you can see far off over the sea its going to rain. When bad weather approaches the air pressure decreases making the air clearer.

"Red sky at morning, sailor take warning" and "red sky at night, sailors delight" comes from the fact that the morning sun turns the eastern sky red as storms approach. When the storm leaves, moving east, the clouds turn red as clearing skies open to the setting sun.

Other signs to observe for is when the sea birds fly low to the ground a storm is approaching. A rainbow marks the end of a storm. When the cows lay down under the trees rain is near.

Forecasting is difficult, and weather changes rapidly. If the dive team uses the signs of nature, with a weather radio they can possibly stay one jump ahead of foul weather.

The most frequent storm is the thunderstorm, and everyday thunderstorms present the biggest problem to the rescue team. If a vessel is going to wreck, or be lost, it will most likely be during a storm. They can come on rapidly, and depart as fast as they sprang up. They normally are preceded by dramatic cloud formations with fluffy cumulonimbus clouds and can have large volumes of rain, with lighting, and thunder. Lighting hits the highest object in its path so boats on open water are at risk. Hail sometimes may accompany these storms.

Tornadoes are the most violent form of thunderstorms and on water are called water spouts. These are funnel shaped windstorms with spinning winds up to 400 miles per hour. Their paths are narrow, never over a couple of hundred yards wide. When a tornado watch is in affect it means the weather conditions are right for them to occur. To the rescue team it means to use extreme caution on the water for the risk is high. If a tornado warning is in affect it means that actual tornadoes have been spotted, and the danger is even greater.

For over 100 years, display stations were established at yacht clubs, marinas, and Coast Guard stations to hoist flags, pennants and colored lights to warn mariners of storms at sea. The display stations were individually notified by the National Weather Service to raise the signals and again to lower them when the hazards passed. The National Weather Service paid for the visual signals; however, the display stations were operated by other agencies or volunteers. Due to budget cuts the National Weather Service stopped the individual notification and switched to the NOAA Weather Band RadioNOAA Weather Radio covers the coastal areas of continental United States, Alaska, Hawaii, and the Mariana Islands with continuous weather broadcasts. Currently U.S. Coast Guard and other stations continue to display warning signals without the direct participation of the National Weather Service. Signals are displayed at many locations such as fire stations and public buildings once NOAA issues the alert on the weather band.

SMALL CRAFT

ADVISORY

GALE

WARNING

STORM

WARNING

HURRICANE

WARNING

NIGHT

NIGHT

NIGHT

NIGHT

Explanation of Warnings Issued by NOAA

A SPECIAL MARINE WARNING is issued whenever a severe local storm or strong wind of brief duration is imminent and is not covered by existing warnings or advisories. No visual displays will be used in connection with the Special Marine Warning Bulletin; boaters will be able to receive these special warnings by keeping tuned to a NOAA Weather Radio station or to Coast Guard and commercial radio stations that transmit marine weather information.

SMALL CRAFT ADVISORY: To alert mariners to sustained (more than two hours) weather or sea conditions, either present or forecast, that might be hazardous to small boats. If a mariner notices a Small Craft Advisory pennant displayed he should determine immediately the reason by tuning his radio to the latest marine broadcast. Decision as to the degree of hazard will be left up to the boatman, based on his experience and size and type of boat. The threshold conditions for the Small Craft Advisory are usually 18 knots of wind (less than 18 knots in some dangerous waters) or hazardous wave conditions.

GALE WARNING: To indicate winds within the range 34 to 47 knots are forecast for the area.

STORM WARNING: To indicate winds 48 knots and above, no matter how high the speed, are forecast for the area. However, if the winds are associated with a tropical cyclone (hurricane), the STORM WARNING indicates that winds within the range 48-63 knots are forecast.

HURRICANE WARNING: Issued only in connection with a tropical cyclone (hurricane) to indicate that winds 64 knots and above are forecast for the area.

"HURRICANE WATCH" is an announcement issued by the National Weather Service via press and television broadcasts whenever a tropical storm or hurricane becomes a threat to a coastal area. The "Hurricane Watch" announcement is not a warning, rather it indicates that the hurricane is near enough that everyone in the area covered by the "Watch" should listen to their radios for subsequent advisories and be ready to take precautionary action in case hurricane warnings are issued.

Every June through November the storm season comes around, so at the start get prepared. Recheck your supplies of lines and extra batteries, tools, safety equipment, anything you may need for a major disaster. Do not wait until a storm approaches to get ready, by then it is to late. Now is the time to preplan for a hurricane just as you would for any other operations.

Major storms cause unique problems for the dive team. By international agreement, tropical cyclone is the generic term for all cyclonic circulation originating over tropical waters. The degree of severity is indicated by what the storm is called or its type. A TROPICAL DISTURBANCE is a rotary circulation storm that does not have or only slightly has rotary winds at the surface, but better developed winds aloft or up high. It is without closed isobars (lines of equal atmospheric pressure) and without strong winds. They are a common occurrence in tropical regions such as the Gulf coast.

A TROPICAL DEPRESSION is similar to a tropical disturbance but has one or more closed isobars and mild rotary circulation at the surface. Winds associated with a tropical depression may be as high as 34 knots (39 mph). When the wind speed increases the depression will develop a distinct rotary circulation pattern and close all isobars. Once this happens it is reclassified as a TROPICAL STORM and given a name, such as tropical storm Dona. The wind speed of this type of storm is from 34-63 knots or 40 to 74 mph. Once the wind speed exceeds 64 knots (74 mph) the storm becomes a HURRICANE.

When a storm is moving into an area NOAA issues an advisory to warn small craft operators to take precautions and not to venture out, this is a SMALL CRAFT ADVISORY. When the approaching storm has winds from 38 to 55 miles per hour NOAA adds a GALE WARNING to the Small Craft Advisory.

Once an approaching storm has winds from 55 to 74 miles per hour and is a few hundred miles off a STORM WARNING is added to the advisory. A Storm Warning when issued will give a coastal range that is affected by the warning, how long the warning is in affect and the expected intensity of the storm. If the winds of the approaching storm are part of a tropical cyclone advisory, then changes may be made to TROPICAL STORM WARNING, or a HURRICANE WARNING.

When a hurricane threatens a coast a HURRICANE WATCH is put into affect. A hurricane watch indicates that the chance of the area getting hurricane force winds is a real possibility; however, it does not mean a hurricane is imminent.

Once conditions are such that a hurricane may hit an area within 24 hours a HURRICANE WARNING is issued. A warning also may describe costal areas in which dangerously high water or exceptionally high waves are forecast. All precautions for a hurricane should be taken immediately. A Hurricane Warning is seldom issued greater than 24 hours before expected land fall. When the path of the hurricane is slow or erratic and unusual the warning may only be a few hours before the beginning of hurricane conditions. For this reason precautions should be taken during the hurricane watch.

Hurricanes are graded by the Saffir/Simpson scale. This scale is an index that attempts to relate hurricane intensity to damage potential. This descriptive scale ranges from 1 to 5 with 5 being the worst. The scale is summarized below:

CATEGORY I: Wind speeds of not less than 74 nor greater than 95 miles per hour. This category hurricane will primarily damage shrubbery, foliage, trees, and minor damage to mobil homes. No severe damage to other structures but there may be damage to signs. Storm surge will be 4 to 5 feet over normal. Low-lying roads inundated, minor pier damage and some small craft may be pulled from moorings.

CATEGORY II: Winds from 96 to 110 miles per hour. There will be considerable damage to trees, foliage, and mobil homes. There may be extensive damage to signs with some being blown down. There will be minor damage to buildings roofing materials with some windows being blown out. No real major damage to buildings. Storm surge is 6 to 8 feet above normal. Coastal roads may be cut off by water 2 to 4 hours before arrival of the hurricane's eye. There will be considerable damage to piers and marinas. Small craft may be torn from moorings. Evacuation of shoreline residences and low-lying areas are recommended.

CATEGORY III: Winds from 111 to 130 miles per hour. Large trees may be blown down. Almost all poorly constructed signs will be blown away. Some damage to buildings especially roofs and windows, minor structural damage may occur. Mobil homes may be destroyed. Storm surge 9 to 12 feet above normal. Major flooding of coastal areas 3 to 5 hours before arrival of the eye. Minor erosion to beaches and shoreline. Flat terrain 5 feet or less above sea level flooded inland 8 miles or more. Massive evacuation of residences from shore and low-lying areas is highly recommended.

CATEGORY IV: Winds 131 to 155 miles per hour. Trees and most signs blown down. Extensive damage to buildings. Many small residences may be seriously damaged. Complete destruction of mobil homes. Storm surge 13 to 18 feet above normal. Flat terrain 10 feet or less above sea level flooded as far as 6 miles from shore. Low lying areas will flood 3 to 5 hours before hurricane center arrives. Major erosion of beaches and shoreline. Massive evacuation of residences from shore and low-lying areas is highly recommended.

CATEGORY V: Wind speed greater than 155 miles per hour. Considerable damage to trees shrub, signs and buildings. Extensive shattering of glass. Some building will collapse or be blown away. Complete destruction of mobil homes. Travel impossible. Storm surge greater than 18 feet above normal. Major flooding to all areas less than 15 feet above sea level. Major erosion of beaches and shoreline. Massive evacuation of residences from shore and low-lying areas is highly recommended.

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