Hurricane forecasters lack intensity skill

Although the National Hurricane
Center in Miami has made tremendous strides in predicting the track of tropical
cyclones over the past decade, it still cannot the predict intensity of storms
with much skill. 

Lixion Avila, the senior hurricane
specialist at the National Hurricane Center, spoke about the intensity
prediction difficulties last week while here as part of the visit of the
WC-130J Hercules Hurricane Hunter aircraft. 

“We have lots of very good models
to predict track,” Mr. Avila said, noting that the error distance five days out
is now that same as it was three days out 10 years ago. 

“For intensity, we only have a few [models]
and none of them are very good.” 

The lack of progress in predicting
intensity was underscored in 2007 with Hurricane Felix, which intensified from
a Category 1 to a Category 5 in one day, a strengthening the National Hurricane
Center didn’t see coming. 

Because of the lack of skill in
predicting tropical cyclone intensity, Director of the National Hurricane
Centre Bill Read,  who was also in Cayman
as part of the Hurricane Hunter visit, said people shouldn’t become fixated
with a storm’s category as defined by the Saffir-Simpson Hurricane Scale. 

“The purpose of the scale is to
warn people of potential impact,” he said, noting however, that there was no
way conveying what the actual impact of a storm would be. 

Because some people make decisions
based on the category of a hurricane, they might not take the appropriate
actions to prepare.   

Mr. Read talked
about Tropical Storm Allison in 2001, which dumped as much as 40 inches of rain
on Texas, killing 23 people, destroying 2,744 homes and causing $5.5 billion of
damage. 

He also spoke about Hurricane Ike, which although it was only a Category
2 storm on the Saffir-Simpson scale, was an enormous storm that killed at least
195 people and caused $29.6 billion of damage, the third costliest hurricane
ever to make landfall in the United States. 

“If I had it to do again, I
wouldn’t have a scale,” Mr. Read said. 

Cayman Islands National Weather
Service Director-General Fred Sambula agreed that the Saffir-Simpson scale
could give people a false sense of security. 

“Don’t worry about the scale too
much,” he said. “Worry about the potential damage.” 

Speaking about track forecasts, Mr.
Read said many people would likely say that the National Hurricane Center’s
track forecast 96 hours before landfall for Hurricane Ike in 2008 was not a
good forecast, even though it made landfall well within the forecast error for
four days out. 

He stressed that people living in a location that falls within
track cone of uncertainty should prepare and not concentrate on the forecast
track line. 

“We need to get people away from
thinking that magic skinny line is real,” he said. 

Despite a trend for lower numbers
of fatalities resulting from tropical cyclones – mainly because of modern
communications and advance warning systems – Mr. Read said the dollar amount of
damage has been trending upwards.  

This is a result of not only more growth
along coastlines, but also because of larger and more expensive homes being
built along the coast. 

  

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