Erin lives in hurricane territory and I
live in tornado country. Both are destructive weather events, but they
differ in several aspects while sharing a few others.
Hurricanes
Hurricanes generally emerge from the
Atlantic Ocean (they're called typhoons if they are in the Pacific
Ocean) and are huge storms that move fairly slowly carrying lots of
rain and high winds. When a hurricane makes landfall it wreaks havoc
over a wide area; “storm surge” is the term for waves carried
along by the hurricane that are many times as high as normal waves,
carrying seawater inland and adding to the flooding caused by the
torrential rain. Hurricanes are classified by their sustained wind
speeds rather than their footprint, making comparisons difficult; A concentrated, high-energy storm may cause more extensive damage in a
smaller area but a slightly “weaker” storm that covers a wide
area will cause more total damage. Think of it as a rifle versus a
shotgun; you don't want to get hit by either one, but the rifle has a
much narrower path of damage whereas shotguns can hit multiple targets.
Strength Classification
The hurricane classification system
uses five “categories” of sustained winds stronger than a typical
storm:
- A Tropical Depression is a storm with
sustained winds below 38 mph.
- Between 39 and 74 mph, it's called a
Tropical Storm.
- Between 74 and 95 mph, it's a Category
(Cat) 1 hurricane.
- Between 96 and 110 is Cat 2.
- Between 111 and 129 is Cat 3.
- Between 130 and 156 is Cat 4.
- Anything over 157 mph is Cat 5.
Planning & Preparation
Hurricanes damage a wide area with wind and water, making recovery a state-level project. Restoring power is one of the main goals of hurricane recovery, since a large area is impacted and it's usually a heavily populated area as well.
Preppers need to be able to take care of themselves and their families for days or weeks with limited power, services and transportation. Warnings are normally given a day to a week before the storm hits, so you can decide to leave or stay and you have time to top off supplies.
Tornadoes
Tornadoes are mostly a Great Plains weather
event, as the conditions for their formation are unlikely in mountainous
or forested areas. Hurricanes often spin off tornadoes to add insult
to injury, so the two can be found together, but the singular or
small cluster versions are more common in the Central Plains of the
USA. Europe has smaller tornadoes and they're very rare, while those
of us in Tornado Alley get multiple severe ones every year. Being far
from the coasts, flooding is less of a problem, so most of the damage
they inflict is from wind.
Strength Classification
Tornadoes are ranked by both wind speeds and damage potential. Named the Fujita (F) Scale after the scientist
that created it, it's a scale from 0 to 5. Wind speeds are easy to
measure, but damage is a bit more random, so the F scale is more of a
“rule of thumb”.
- A normal thunderstorm
will usually have winds under ~70 mph, with little to no rotation of
the storm. Once it starts spinning on itself, the winds pick up
rapidly and things start to fly.
- At 73 mph, we've hit
F0 and can expect light damage to trees and buildings.
- Between 74 and 112
mph it's an F1. Shingles start leaving roofs, cars are pushed off
roads, and mobile homes become more mobile.
- Between 113 and 157
mph it's an F2. Entire roofs are ripped off houses, train cars are
knocked over, and large trees uprooted or snapped. Lawn furniture and
light objects become missiles.
- Between 158 and 206
mph it's an F3. Walls start following the roofs into the air,
locomotives are pushed over, and flying cars become reality.
- Between 207 and 260
mph it's an F4. Wood-frame buildings demolished, airborne missiles
cause major damage.
- Between 261 and 318
mph it's an F5. Entire houses lifted into the air, car-sized missiles
created by debris are common.
Looking at the two scales, you'll
notice some overlap in wind speeds. A Cat 4 hurricane has roughly the
same winds as a F2 tornado, as an example. The two aren't comparable, though, because a Cat 4 hurricane will have a diameter measured in dozens or
hundreds of miles while any tornado will be measured in feet or yards
(the largest tornado on record was about 1.5 miles in diameter).
Tornadoes also have drastically shorter lifespans and paths; while a
hurricane can last for a few days and travel a few hundred miles
inland before dying out, most tornadoes last only a few minutes and
travel a few miles. Hurricanes grow slowly and are tracked as they
approach land, but tornadoes pop up suddenly, almost at random, and are
over by the time they start to be tracked.
Planning and Preparation
Tornadoes devastate a small area with
winds up to twice as high as a hurricane. The damage is more
concentrated and more severe, meaning recovery is either minimal or
impossible.
Utilities are normally restored within hours or days, but
if your house was in the path it may not exist any more. I've seen
neighborhoods after a tornado, and you can have a house standing there
with minor roof damage next to a vacant lot where his neighbor's
house used to be.
Warnings are given only slightly before (and sometimes after)
the tornado hits. When conditions are ripe for their formation the
local weather-people will give the normal watch/warning speeches, but
like the little boy who cried “Wolf!” they are ignored. Local
warning sirens are the best we have, and they give you minutes (at best) to find
shelter. Having a suitable shelter close by and good
insurance is about all you can do to prepare for a tornado.
Hurricane season has a few months left, but tornado season is drawing to a close. We had a fairly quiet
summer in my area this year but we're still dealing with damage from
last year's “inland hurricane” that hit a wide swath of the state
with Cat 1 winds. Keep an eye on the sky, and research the weather
patterns for your area, so that you are less likely to be caught by
surprise.
