HURRICANE? CYCLONE? TYPHOON
HURRICANE? CYCLONE? TYPHOON? They're all the same,
officially tropical cyclones. But they just use distinctive terms for a storm
in different parts of the world. Hurricane is used in the Atlantic, Caribbean
Sea, central and northeast Pacific. They are typhoons in the northwest Pacific.
In the Bay of Bengal and the Arabia Sea, they are called cyclones. Tropical
cyclone is used in the southwest India Ocean; in the southwestern Pacific and
southeastern India Ocean they are severe tropical cyclones.
STRENGTH: A storm gets a name and is considered a tropical
storm at 39 mph (63 kph). It becomes a hurricane, typhoon, tropical cyclone, or
cyclone at 74 mph (119 kph). There are five strength categories, depending on
wind speed. The highest category is 5 and that's above 155 mph (249 kph). Australia
has a different system for categorizing storm strength.
ROTATION: If they are north of the equator they rotate
clockwise. If they are south, they rotate counter-clockwise.
SEASON: The Atlantic and central Pacific hurricane seasons
are June 1 through Nov. 30. Eastern Pacific: May 15 to Nov. 30; northwestern
Pacific season is close to all year, with the most from May to November. The
cyclone season in the south Pacific and Australia runs from November to April.
The Bay of Bengal has two seasons April to June and September to November.
WHERE IS THE BUSIEST PLACE? The northwestern Pacific where
Typhoon Haiyan has just hit. A normal year there involves 27 named storms.
Haiyan is the 28th named storm and there has already been a 29th. By comparison
the Atlantic averages 11 named storms a year and this year there have been 12,
none of them causing major problems.
WHO DECIDES THE NAMES? The lists are maintained by the
World Meteorological Organization; the names are ones that are familiar in each
region. Names are taken off the list and replaced to avoid confusion if a
hurricane causes a lot of damage or deaths. For example, Katrina was retired
after it devastated New Orleans in 2005. The Philippines has its own naming
system, so Typhoon Haiyan is also being called Yolanda.
HOW DOES EL NINO AFFECT STORMS? During an El Nino — when
the central Pacific is warming — there are fewer Atlantic storms. El Ninos
shift where storms form, but not the number, for the northwest Pacific and the
southwest Pacific. The central Pacific gets more storms during El Nino and the
year after. This year has neither an El Nino nor its opposite, a La Nina. It is
a neutral year.