2016 Hurricane Preparedness - Winds & Tornadoes

High Winds from Hurricanes

We continue our coverage of the 2016 Hurricane Preparedness Week by looking at two more of the hurricane hazards.  In particular, we'll look at High Wind and Tornadoes.

 

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Cat.	Speed (mph)
1	74-95
2	96-110
3	111-129
4	130-156
5	>157

The intensity of a landfalling 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.  A summary chart is shown here. More details were covered in 2014 Hurricanes - How They Work.

RELATED INFORMATION

• HIGH WIND SAFETY ACTIONS
• SAFFIR-SIMPSON HURRICANE SCALE (updated  2012)
• HURRICANE WIND DECAY
• HISTORIC HIGH WIND EVENTS
• RISK AREAS

Tornadoes 

A tornado is a dark funnel-shaped cloud made up of violently rotating winds that can reach speeds of up to 300 m.p.h. The diameter of a tornado can vary between a few feet and a mile, and its track can extend from less than a mile to several hundred miles. Tornadoes can occur any time, with many occurring in spring or early summer.

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 rainbands, well away from the center of the hurricane.

Tornado Facts

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

The Fujita Scale

F-Scale Number	Intensity Phrase	Wind Speed	Type of Damage Done
F0	Gale tornado	40-72 mph	Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.
F1	Moderate tornado	73-112 mph	The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed.
F2	Significant tornado	113-157 mph	Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated.
F3	Severe tornado	158-206 mph	Roof and some walls torn off well constructed houses; trains overturned; most trees in fores uprooted
F4	Devastating tornado	207-260 mph	Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.
F5	Incredible tornado	261-318 mph	Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel re-inforced concrete structures badly damaged.
F6	Inconceivable tornado	319-379 mph	These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies