The scoop on tropical storms vs. hurricanes

The scoop on tropical storms vs. hurricanes

By Scott Sistek

I figured with Tropical Storm Fay in the news wandering around Florida, now might be a good time to chat about hurricanes and tropical storms and answer some frequently asked questions we get in the ol' e-mail bin:

1) What is the difference between a "Tropical Storm" and a "Hurricane"?

It's all about the wind. A hurricane is any tropical based storm that has wind speeds greater than 74 mph. A "tropical storm" is a storm with winds of 39-73 mph. A "tropical depression" is when the Florida Marlins lose to the Atlanta Braves -- or when a storm is tropical in nature, but has winds under 39 mph.

We only name the storms when they get to "tropical storm" strength or higher. Tropical depressions just get plan numbers like "Tropical Depression 3". I guess that's because we only have 21 names and we don't want to run out as they are more common.

2) So, then what's a typhoon?

That is a hurricane, just in a different part of the world. The term "hurricane" is used for storms in the North Atlantic, Northeast Pacific Ocean east of the International Dateline, or the south Pacific Ocean east of 160 degrees East longitude.

A typhoon is a storm in the northwestern Pacific west of the International Dateline -- i.e., storms that strike the northeast Asian coasts like Japan, China and Taiwan.

A cyclone is officially a hurricane/tropical storm that occurs in the Indian Ocean. Although the term has also become colloquially associated with tornadoes in the Midwest, but that is not an official definition. Cyclone Nargis was in the news recently when it hit Myanmar.

3) Fay? Cristobal? Dolly? Who Names These Things?

The World Meteorological Organization is in charge of selecting names for hurricanes. It was developed in the 1950s to make it easier to communicate storms to the public and mariners (instead of "that big storm at 34.423 degrees N and 78.232 degrees West, oops now 78.233").

It used to be just women's names were used, but in 1979, it was decided that men shouldn't miss out on being picked on for having a storm named after them, so now it alternates male/female. (And as of yet, no "Scott" on the list, whew!)

There are six lists that rotate every six years. When a hurricane does massive destruction, (like Katrina) the name is retired and a new name replaces it, (welcome, "Katia"). (See list of retired names here)

In the Atlantic Ocean, storm names are a mix of Anglo/English, Spanish and French names in deference to the languages of the countries that these hurricanes typically strike. A separate list is maintained for the Pacific Ocean, and there are several other lists used for storms in other parts of the world, again using names more common to each region. That link above has the entire lists.

As to how they come up with the names, that is a closely guarded secret. They typically pick names that are easy to understand, but beyond that, the WMO huddles in a corner and then mysteriously comes out with the names. (There's no truth to the long-standing rumor that it's ex- boy/girlfriend names of those on the panel :) )

What Happens When We Run Out Of Names?

You'd think with 21 names available that'd be enough. (We skip "Q", "U", "X", "Y" and "Z" just due to lack of names that start with those, or meteorologists just don't date very many Zekes, Yolandas or Xaviers.) Up until 2005, we'd never gotten past the "T" name. But then 2005 was tropical storm haven, with 27 storms.

But scientists are nothing if not great at planning ahead. The rule was to start using the Greek Alphabet once the next storm formed after "Wilma." So we had Alpha, Beta, Gamma -- all the way up to Zeta, becoming the first Atlantic storm ever to start with a "Z" (and sound like a UW frat at the same time.)

What Steers Hurricanes?

You might be wondering how hurricanes move after watching the meandering track of Tropical Storm Fay, which might be the first tropical system in history that should have been required to have a designated driver. It's made landfall in Florida three separate times, and could possibly make landfall a fourth and *fifth* time along the Gulf Coast.

It's the upper level winds that determine where a hurricane might go, but when you get a situation where the upper level winds are very weak and variable, as they are over the Gulf Coast and Florida right now, storms can drift or meander.

Here's another one with a wacky track: Hurricane Ophelia

There was another one, and I can't find which one it was, where it made landfall into central Florida, then, as if it realized it made a wrong left turn at the light near Vero Beach, actually backed up and out into the Atlantic, and raced north and made landfall again farther north up the seaboard.

4) What does "Category 3" mean?

Hurricanes are rated by top wind speed on the Saffir-Simpson scale. Starting at 75 mph, you go up in category about each 20-25 mph in wind speed. A Category 3, for example, is a storm that has top winds of 111-130 mph. Anything over 155 is a Category 5.

So far, only three "named" Category 5s have ever struck the U.S. -- Hurricane Andrew in 1992, Hurricane Camille in 1969, and the "Labor Day" hurricane that struck the Florida coast in 1935, but that was before storms were given names.

Note that Hurricane Katrina was a Category 5 in the Gulf of Mexico, but weakened to a Category 3 before making landfall at New Orleans. But it was the storm's surge and the levy failures that led to the widespread destruction along the Gulf Coast and New Orleans there, not so much the wind.

Why Don't We Get Hurricanes In The Northwest?

Hurricanes need warm, ocean water to survive, and the water temperatures off the Pacific Coast are generally in the 50-60 degree range -- way too cold for hurricanes to survive. In fact, a hurricane has never struck the Pacific Coast, but a tropical storm once did hit the shores of San Diego.

But We've Had Big Windstorms, Why Aren't They Named?

Washington and Oregon have both had their share of catastrophic windstorms. The storms of December 2006, and 2007, as well as the Inauguration Day Storm of 1993 and the Columbus Day Storm of 1962 have all had wind speeds over hurricane strength.

But those storms were not tropical in nature, so they are not official hurricanes. They are just big storms. We give then calendar or geographic names, but they don't warrant the attention of the World Meteorological Organization -- probably because it would be a nightmare to manage.

And maybe they don't have that many ex's in the group :)

WEATHER NOTE

USFA reports on fire department preparedness for weather emergencies, natural disasters

The United States Fire Administration (USFA) released a new technical report titled Fire Department Preparedness for Extreme Weather Emergencies and Natural Disasters. This report examines the impact of extreme weather and natural disasters on the fire service and the types of service calls most likely to arise as a result of these disasters.

"Firefighters continue to be called upon to respond to many types of incidents, disasters, and situations ? in all kinds of weather, day and night," said U.S. Fire Administrator Greg Cade. "Our country's fire service is an amazing cadre of specially trained individuals whom the public relies on during emergencies--including extreme weather and natural disasters. This requires all firefighters to be prepared to respond in the most challenging conditions."

Fire Department Preparedness for Extreme Weather Emergencies and Natural Disasters also addresses equipment and planning needed in order to be prepared. Safety, mutual aid, shift management, resource identification, logistics, and other related issues are discussed, along with examples from case studies of fire departments that have learned from experience what can happen. The report provides information fire departments can use to enhance their level of preparedness and ensure greater safety the next time disaster strikes.

"September is again the nation's Preparedness Month," continued Cade. "The USFA is pleased to provide this critical information in support of not only this important Department of Homeland Security initiative but also to continue our mission of ensuring the fire service is capable of responding to any and all emergencies, regardless of scope."

The USFA develops reports on selected major incidents throughout the country. The incidents usually involve multiple deaths or a large loss of property, but the primary criterion for deciding to write a report is whether it will result in significant lessons learned. Under this project, USFA also develops special reports addressing a variety of issues that affect the fire service such as homeland security and disaster preparedness, new technologies, training, fireground tactics, and firefighter safety and health.

For additional information regarding this report, or other USFA Technical Reports, CLICK HERE for the report download page.

MARITIME NOTE

Successful Launch for Third INMARSAT-4 Satellite

19th August 2008: Inmarsat, the leading provider of global mobile satellite communications services, has confirmed the successful launch and acquisition of the third Inmarsat-4 satellite.

The satellite was launched on a Proton Breeze M rocket from the Baikonur Cosmodrome in Kazakhstan at 11.43pm BST on 18th August (4.43am 19th August, local time). Inmarsat's tracking station in Fucino, Italy was able to track the satellite while it was still coupled to the Breeze M launch vehicle. Launch provider ILS confirmed successful spacecraft separation at 8.46am BST on 19th August.

The satellite is the third in the I-4 constellation, concluding a decade of development and a $1.5 billion investment. The current constellation of two Inmarsat-4 satellites delivers mobile broadband services to 85 per cent of the world's landmass, covering 98 per cent of the world's population. The third I-4 will complete the global coverage for Inmarsat's broadband services.

Andrew Sukawaty, CEO and Chairman of Inmarsat, said: "The Inmarsat-4s are the world's most sophisticated commercial network for mobile voice and data services, and the successful launch of the third I-4 allows us to complete the global coverage for our broadband services. Once the third I-4 is operational, Inmarsat will have the only fully-funded next-generation network for mobile satellite services."

The Proton Breeze M is one of the few launch vehicles capable of lifting the I-4 satellite � the size of a London double-decker bus and weighing six tons � into geostationary transfer orbit. The I-4 F3 satellite will now undergo a period of deployment and several weeks of comprehensive tests and maneuvers before being positioned in geostationary orbit at 98� West.

Inmarsat satellites are currently relied on by the world's shipping, oil exploration, defense and aviation industries to service their communications needs. Inmarsat is also the communications channel of choice for the media when reporting from the world's danger zones and for NGOs, government agencies and the United Nations when coordinating rescue efforts.

RS