Tropical
Storm Isaac moved into the eastern Caribbean Tuesday afternoon and was moving
westward during the evening. The storm
was getting better organized late in the evening, but the winds were not much
different from earlier in the day. It is
only a matter of time before the winds respond to the drop in pressure.
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| Tropical Storm Isaac at 0215z August 23, 2012. This is an enhanced infrared picture of the storm. The dark areas represent the colder cloud tops meaning that they are higher in the atmosphere. Image Credit: NESDIS. |
There
has been considerable concern about the future of this storm due to the impact
it could have on Florida and the Republican National Convention in Tampa next
week. Any evacuation would greatly alter
the plans for the convention. A general
idea of where the storm is going can be gleaned from the models. However, the devil is in the details. It is far too uncertain at this time frame to
pin down where the storm will strike land.
So
let’s take a look at how the forecasts have fared thus far. The 5-day forecast from the first advisory
early Tuesday morning projected that the storm would continue on generally westward
course until reaching a position south of the Dominican Republic where it would
turn more to the west-northwest.
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| The 5-day forecast from the National Hurricane Center for 0900z August 21, 2012. Click on the image for a larger view. Image Credit: NOAA/NHC. |
The
8 p.m. advisory for Wednesday evening showed the current position plus the
forecast from the late afternoon advisory.
Isaac was clearly south of the forecast as it moved due west instead of
moving west-northwest. This may be due
to the center being located farther south, but the current movement was still
due west.
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Isaac
is moving around the periphery of a large high pressure system to the north. The models have this right, but all over the
models have been too far north in their initial position of the storm. Does this mean that the path should be
shifted south? Yes, albeit a small shift.
Yet, even a small shift at this time frame can make a big difference 5
days from now.
The
latest forecast from the National Hurricane Center projects that Isaac will
start to slowly curve to the west-northwest tonight. If by daybreak it is still moving west, then
it is more likely that the eventual path will be more in the southern half of
the cone of uncertainty (labeled potential track area).
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Note
that I have not said anything about the intensity or changes in intensity. Much depends on the eventual track. If the storm tracks across Hispaniola and the
mountains of Cuba, then the storm will struggle to remain a storm. However, if it stays south of the mountainous
regions, then this storm could become a monster. Conditions will be right for the next several
days for Isaac to intensify. This may be
the most difficult aspect of the forecast because of the possible interaction
with land. Forecasters at the National
Hurricane Center have noted as much.
Fortunately,
Isaac is still days away from the U.S. mainland. It will probably not reach south Florida
before Sunday night. Evacuations from
the Keys may begin by Friday if the storm stays close to its projections. The state of Florida will likely begin
ramping up ongoing emergency operations during the day on Thursday.
It
is still not entirely out of the picture that the storm could turn move
northwest and move through the Bahamas and up the East coast, however this is a
low chance. It is more likely to
eventually move into the Gulf making landfall somewhere in the eastern half of
the Gulf Coast area.
The
main threat to South Carolina could be heavy rains in the middle to latter part
of next week. This would lead to
flooding of rivers and could cause some flash flooding of small creeks. The recent rains mean that the ground may not
be able to absorb as much water leading to more flooding.
All
of this will depend on the path over the next few days. Stay tuned!
