lotus

previous page: 18 During a hurricane are you supposed to have the windows and doors on the storm side closed and the windows and doors on the lee side open?
  
page up: Storms FAQ
  
next page: 20 How are Australian tropical cyclones ranked?

19 How are Atlantic hurricanes ranked?




Description

This article is from the Storms FAQ, by Chris Landsea landsea@aoml.noaa.gov with numerous contributions by others.

19 How are Atlantic hurricanes ranked?

The USA utilizes the Saffir-Simpson hurricane intensity scale (Simpson
and Riehl 1981) for the Atlantic and Northeast Pacific basins to give an
estimate of the potential flooding and damage to property given a
hurricane's estimated intensity:

Saffir-Simpson   Maximum sustained     Minimum surface   Storm surge 
   Category      wind speed (m/s,kt)   pressure (mb)        (m,ft)    
--------------   -------------------   ---------------   ---------------
       1         33-42 m/s [64-83 kt]     >= 980mb       1.0-1.7 m [3-5 ft] 
       2         43-49     [84-96]        979-965        1.8-2.6   [6-8]
       3         50-58     [97-113]       964-945        2.7-3.8   [9-12]
       4         59-69     [114-135]      944-920        3.9-5.6   [13-18]
       5         > 69      [> 135]        < 920          > 5.6     [> 18]

1: MINIMAL: Damage primarily to shrubbery, trees, foliage, and unanchored
homes. No real damage to other structures. Some damage to poorly
constructed signs. Low-lying coastal roads inundated, minor pier
damage, some small craft in exposed anchorage torn from moorings.
Example: Hurricane Jerry (1989)

2: MODERATE: Considerable damage to shrubbery and tree foliage; some
trees blown down. Major damage to exposed mobile homes. Extensive
damage to poorly constructed signs. Some damage to roofing materials
of buildings; some window and door damage. No major damage to
buildings. Coast roads and low-lying escape routes inland cut by
rising water 2 to 4 hours before arrival of hurricane center.
Considerable damage to piers. Marinas flooded. Small craft in
unprotected anchorages torn from moorings. Evacuation of some
shoreline residences and low-lying areas required. Example: Hurricane
Bob (1991)

3: EXTENSIVE: Foliage torn from trees; large trees blown down.
Practically all poorly constructed signs blown down. Some damage to
roofing materials of buildings; some wind and door damage. Some
structural damage to small buildings. Mobile homes destroyed. Serious
flooding at coast and many smaller structures near coast destroyed;
larger structures near coast damaged by battering waves and floating
debris. Low-lying escape routes inland cut by rising water 3 to 5
hours before hurricane center arrives. Flat terrain 5 feet of less
above sea level flooded inland 8 miles or more. Evacuation of low-
lying residences within several blocks of shoreline possibly required.
Example: Hurricane Gloria (1985)

4: EXTREME: Shrubs and trees blown down; all signs down. Extensive
damage to roofing materials, windows and doors. Complete failures of
roofs on many small residences. Complete destruction of mobile homes.
Flat terrain 10 feet of less above sea level flooded inland as far as
6 miles. Major damage to lower floors of structures near shore due to
flooding and battering by waves and floating debris. Low-lying escape
routes inland cut by rising water 3 to 5 hours before hurricane center
arrives. Major erosion of beaches. Massive evacuation of all
residences within 500 yards of shore possibly required, and of single-
story residences within 2 miles of shore. Example: Hurricane Andrew
(1992)

5: CATASTROPHIC: Shrubs and trees blown down; considerable damage to
roofs of buildings; all signs down. Very severe and extensive damage
to windows and doors. Complete failure of roofs on many residences and
industrial buildings. Extensive shattering of glass in windows and
doors. Some complete building failures. Small buildings overturned or
blown away. Complete destruction of mobile homes. Major damage to
lower floors of all structures less than 15 feet above sea level within
500 yards of shore. Low-lying escape routes inland cut by rising water
3 to 5 hours before hurricane center arrives. Massive evacuation of
residential areas on low ground within 5 to 10 miles of shore possibly
required. Example: Hurricane Camille (1969)

Note that tropical storms are not on this scale, but can produce extensive
damage with rainfall-produced flooding. Note also that category 3, 4, and
5 hurricanes are collectively referred to as intense (or major) hurricanes.
These intense hurricanes cause over 70% of the damage in the USA even
though they account for only 20% of tropical cyclone landfalls (Landsea
1993).

Note that in comparison with the Australian scale (subject D2), Australian
1 and and most of Australian 2 are within the tropical storm categorization
(i.e. would not be on the Saffir-Simpson scale). An Australian 3 would be
approximately equal to either a Saffir-Simpson category 1 or 2 hurricane.
An Australian 4 would be about the same as a Saffir-Simpson category 3 or 4
hurricane. An Australian 5 would be about the same as a Saffir-Simpson
category 5 hurricane.

 

Continue to:













TOP
previous page: 18 During a hurricane are you supposed to have the windows and doors on the storm side closed and the windows and doors on the lee side open?
  
page up: Storms FAQ
  
next page: 20 How are Australian tropical cyclones ranked?