Hurricane Wilma Discussion Number 20

Statement as of 5:00 am EDT on October 20, 2005

as anticipated...Wilma is going through the weakening phase of an
eyewall cycle. This is based on microwave data and observations
from a reconnaissance plane which reported excellent radar
presentation of concentric eyewalls of 4 and 40 N mi in diameter
respectively. The plane also observed two maximum wind
with winds of 121 knots...and a minimum pressure of 903 mb measured
by a sonde...but with 23 knots at the surface. The pressure could
then be a few millibars lower. Satellite images indicate that
the cloud pattern is not as spectacular as it was 12 to 18 hours
ago and in fact...the eye is obscured at this time. The initial
intensity is adjusted down to 130 knots. This may be an overestimate
since the maximum winds reported so far are 121 knots. However...we
are assuming that the plane has not sampled the entire circulation.

We do not know exactly when and if the strengthening phase of the
eyewall replacement cycle will begin. Since it is assumed that it
will occur within the next 12 to 24 is
forecast during this period. I would not be surprised if we see the
formation of a large eye later today. Thereafter...a portion of the
circulation will be interacting with the Yucatan Peninsula and
there will be increasing wind shear. Wilma should then begin a
steady weakening trend.

The expected northwest turn has not materialized yet and the average
motion of Wilma is still 295 degrees at 7 knots. However...the
northwest motion should begin soon as the short wave over the west
central United States advances rapidly eastward. This wave is
expected to create a weakness over the Gulf oe Mexico and Wilma
should turn to the northwest and north toward the weakness. The
short-wave is expected to amplify and bring the westerly flow south
enough to carry Wilma toward the northeast. Before the westerlies
become established...the steering currents are expected to be weak.
Wilma will likely meander for a day or so over northeastern Yucatan
or the Yucatan Channel before taking off toward the northeast as in
a typical recurvature pattern.

Track guidance is showing the usual variability but the overall
model consensus is to keep Wilma moving very slowly near or over
northeastern Yucatan for the next two days and then sharply turning
the hurricane toward the northeast. It is fair to say that by day
five...Wilma should begin to acquire extratropical characteristics
by judging the expansion of the wind field and the frontal like
moisture pattern in models.

Forecaster Avila