Ivan rated Category 4 by weather service

Published 12:00 am Friday, September 17, 2004

As Hurricane Ivan approaches the Gulf Coast, area residents are hearing a great deal about category, wind speed and rainfall potentials.

All relate to how dangerous the storm’s move through the area will be.

At 3:30 p.m. Tuesday, the National Weather Service issued the first watch of Ivan’s approach with a flash flood watch.

The rainfall potential for the Greenville area is 14-16 inches.

This creates very deadly highway conditions for anyone who dares drive at the height of the storm.

As Ivan begins to beat his path toward Alabama officials at the Calera office of the National Weather Service are hunkered over their radar screens like they’re looking for enemy aircraft. So far, they don’t like

what they’re seeing.

&uot;This is a very serious situation,&uot; Meteorologist in Charge Ken Graham said noting the seriousness spreads far beyond the Gulf Coast.

&uot;What that means for Greenville is lots of strong wind and rain. Graham said Gale force winds (39 mph) by early tomorrow morning. By late Thursday, tropical storm force winds (58 mph) are expected.

&uot;At that time there could be some hurricane gusts anytime during the night Thursday night and early Friday morning.&uot;

All the heavy winds will be accompanied by heavy rainfall. Graham said Butler County could expect from 8-to 12-inches of rain and which could fluctuate as the days pass.

So what does it mean when forecasters say it is a Category 4 storm?

Saffir-Simpson Hurricane Scale

According to the National Weather Service, the intensity of a land falling hurricane is expressed in terms of categories that relate wind speeds and potential damage. According to the Saffir-Simpson Hurricane Scale, a Category 1 hurricane has lighter winds compared to storms in higher categories. A Category 4 hurricane would have winds between 131 and 155 mph and, on the average, would usually be expected to cause 100 times the damage of the Category 1 storm. Depending on circumstances, less intense storms may still be strong enough to produce damage, particularly in areas that have not prepared in advance.

N Tropical Storm – Winds 39-73 mph

N Category 1 Hurricane – winds 74-95 mph (64-82 kt)

No real damage to buildings. Damage to unanchored mobile homes. Some damage to poorly constructed signs. Also, some coastal flooding and minor pier damage. Examples: Irene 1999 and Allison 1995

N Category 2 Hurricane – winds 96-110 mph (83-95 kt)

Some damage to building roofs, doors and windows. Considerable damage to mobile homes. Flooding damages piers and small craft in unprotected moorings may break their moorings. Some trees are blown down. – Examples: Bonnie 1998, Georges 1998 and Gloria 1985

N Category 3 Hurricane – winds 111-130 mph (96-113 kt)

Some structural damage to small residences and utility buildings. Large trees blown down. Mobile homes and poorly built signs destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain may be flooded well inland. Examples: Fran 1996, Opal 1995,

n Category 4 Hurricane – winds 131-155 mph (114-135 kt)

More extensive curtainwall failures with some complete roof structure failure on small residences. Terrain may be flooded well inland. Examples: Hugo 1989 and Donna 1960

N Category 5 Hurricane – winds 156 mph and up (135+ kt)

Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Massive evacuation of residential areas may be required. Examples: Andrew (FL) 1992, Camille 1969 and Labor Day 1935.

High Winds

Tropical storm-force winds are strong enough to be dangerous to those caught in them. For this reason, emergency managers plan on having their evacuations complete and their personnel sheltered before the onset of tropical storm-force winds, not hurricane-force winds.

Hurricane-force winds can easily destroy poorly constructed buildings and mobile homes. Debris such as signs, roofing material, and small items left outside become flying missiles in hurricanes. Extensive damage to trees, towers, water and underground utility lines (from uprooted trees), and fallen poles cause considerable disruption.

The strongest winds usually occur in the right side of the eye wall of the hurricane. Wind speed usually decreases significantly within 12 hours after landfall. Nonetheless, winds can stay above hurricane strength well inland. Hurricane Hugo (1989), for example, battered Charlotte, North Carolina (which is 175 miles inland) with gusts to nearly 100 mph.


Hurricanes can also produce tornadoes that add to the storm’s destructive power. Tornadoes are most likely to occur in the right-front quadrant of the hurricane.

However, they are also often found elsewhere embedded in the rain bands, well away from the center of the hurricane.

Some hurricanes seem to produce no tornadoes, while others develop multiple ones. Studies have shown that more than half of the land falling hurricanes produce at least one tornado; Hurricane Beulah (1967) spawned 141 according to one study. Nonetheless, the effects of tornadoes, added to the larger area of hurricane-force winds, can produce substantial damage.

There is no way at present to predict exactly which storms will spawn tornadoes or where they will touch down. The new Doppler radar systems have greatly improved the forecaster’s warning capability, but the technology usually provides lead times from only a few minutes up to about 30 minutes. Consequently, preparedness is critical.

N When associated with hurricanes, tornadoes are not usually accompanied by hail or a lot of lightning, clues that citizens in other parts of the country watch for.

N Tornado production can occur for days after landfall when the tropical cyclone remnants maintain an identifiable low-pressure circulation.

N They can also develop at any time of the day or night during landfall. However, by 12 hours after landfall, tornadoes tend to occur mainly during daytime hours.

Inland Flooding

When you hear hurricane, think inland flooding.

N Determine whether you live in a potential flood zone.

N If advised to evacuate, do so immediately.

N Keep abreast of road conditions through the news media.

N Move to a safe area before access is cut off by floodwater.

N Do not attempt to cross-flowing water. As little as six inches of water may cause you to lose control of your vehicle.

N Develop a flood emergency action plan.

N Have flood insurance. Flood damage is not usually covered by homeowners insurance.

Do not make assumptions.

Check your policy.

The Clanton Advertiser and the National Weather Service contributed to this report.