It would appear that everyone watching the travels of Hurricane Ivan were on
the wrong path.
The United States National Hurricane Center’s report on Hurricane Ivan
contains a section headed ‘Forecast and Warning Critique’ and notes that the
National Hurricane Center’s official track forecast was at most times
outperformed during Ivan by the UKMET and FSU Superensemble numerical track
The official track forecasts, it notes, “had, in general, a persistent
right–of–track bias for the first 11 days of Ivan’s existence as a tropical
This right–of–track bias of the official forecast had Ivan turning north
farther east, or right, of the Cayman Islands because it relied on global models
that showed a strong subtropical ridge north of Ivan eroding more quickly than
it ultimately did.
Although some residents of the Cayman Island have spoken of Ivan “bouncing
off the mountains of Jamaica,” the report gives another possible explanation:
“The westward jog that Ivan made on 11 September appears to be, at least in
part, the result of a mid–to–upper–level cold low to the north of Hispaniola
that moved slowly southwestward rather than weakening and lifting out to the
northeast as some of the models had been forecasting.”
Director of Meteorological Services Fred Sambula said in a recent interview
that it is not possible to predict a hurricane’s path with any certainty. “It’s
going to be an on–going argument as to which model does better,” he said. “One
of the flaws in computer models is that they tend to base their conclusions on
the assumption that all hurricanes will behave as others did.
“We’ve tried to model the atmosphere, but there are so many variables that
affect the time and space path of a hurricane. We try to take one element,
temperature for example, and determine what effect it will have on a hurricane’s
path, not really knowing how it will interact with some of the other elements,”
“Instead of looking at one variable, maybe we should be looking at them all,
but our computer models aren’t up to that capability yet,” he concluded.
The difficulty in predicting a hurricane’s path underscores a common
“We look at the line of a hurricane’s predicted path and tend to focus on
that point,” Mr. Sambula said. “A hurricane is not a point. In truth, a
hurricane is a wide area of destruction. If it was heading for Cayman Brac and
was 400 miles across, of course we should have been concerned in Grand
Chief Meteorologist Jeff Tibbetts agrees, pointing out that predicted
hurricane paths also show a wider margin of error area in which the hurricane
could conceivably travel. “If you are anywhere within that error band, it means
that we should start a high level of preparation,” he said.