OCT 19, 2005 / 12:55AM UPDATE #5
NHC 'ONLY' UPGRADES TO CAT 4-
BUT WILMA IS A DEVASTATING CAT 5 HURRICANE
PRESSURE FALL OF OVER 50mb IN 5 HOURS
PERSONALLY ADVISE ALL FLORIDA KEYS RESIDENTS TO EVACUATE
Air Force RECON recently found the central pressure had fallen to 901mb -- just a few MB above RITA record, and 1mb
lower than Katrina -
at their Peak Intensity. The maximum Flight level winds were 162KTs in the NE quadrant, and being
conservative, this is 160mph sustained surface winds. However -- as politics would dictate -- NHC has only upgraded
the hurricane to a CAT 4, with 150mph sustained winds - 5mph below that of a CAT 5. In the Atlantic basin, pressures
below 920mb are normally associated with a CAT 5 hurricane. The storm is located at at 16.9N/82.0W and is moving NW at 5Kts.
Cloud top temps are near -87°C As cold as the temps ever get -- or at least as cold as the scale permits....
There will be several more measurements made during the next couple of hours -- but they will be difficult to take -- the eye is a mere 4NM
in diameter. I don't recall ever seeing a report of under 5NM. There is in fact, almost no room to maneuver the A/C. The pressure
was extrapolated -- from FLT Level -- but I am uncertain precisely what that level was, though it appears they came in at about 1,200 feet.
The crew also just reported they climbed to 700mb within the eye for 'safety reasons'. That would presumably work out to around
5500ft. Just prior to penetrating the eyewall, the crew reported an East wind 158kts and a surface pressure of 899mb -- and that alone doesn't make sense. One of the 2 pressure readings were wrong by a few millibars. With the eye so small, the eyewall will have to be replaced within the hour -- and whether the pressure will again fall to this level is impossible to know.
The 00Z models are now even more tightly clustered a=on a landfall on the SW coast of Florida in 96 hours -- Saturday morning.
It is safe to assume it will be a major, CAT 3 hurricane at landfall.
The next update will be late Wed AM -- with a brief update around 9AM.
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Remarkable image of a 4NM wide eye -- at cloud top temps near the end of the scale at -87°C
My prior forecast track stands -- across the Everglades, and emerging off the coast near Ft. Lauderdale. This time around, the forward
motion of the storm is nearly identical among all the models. Besides the issue of max winds at the time of landfall, there is a positive aspect
to the track the storm is taking relative to the Florida coast -- it will not produce the type of extreme storm surge caused by Katrina or Rita. The seafloor topography is different, and the fetch and duration of the strong winds will not be sufficient to cause the build up of the storm
surge that the other 2 storms were able to produce.
____________________________________________________________________________________
OCT 18, 2005 / 11:48PM SPECIAL URGENT UPDATE #4
RECON JUST REACHED. WILMA IT IS AN UNBELIEVABLE SUPER CAT 5 --> 901MB, WITH 162kts!!!!
OVER A 50mb DROP IN 5 HOURS - THE SAME RATE AS RITA. 2 MORE HOURS OF THIS IT COULD EASILY BREAK THE ALL TIME
RECORD LOW PRESSURE IN THE ATLANTIC BASIN OF 888MB.
IMAGERY SUPPORTS THIS. And the 850mb height was reported at 516 meters. The pressure reading was extyrapolated -- and we should see a dropsonde reading shortly.
I will continue to update this section during the next hour.
Steve
___________________________________________________________________________________________
OCT 18, 2005 / 9:58 PM - SPECIAL URGENT UPDATE
HURRICANE WILMA OFFICIALLY CAT 2 - INTENSIFYING RAPIDLY
STROM WILL Likely ATTAIN CATEGORY 4 STATUS WITHIN 12-24 HOURS
STRIKE SOUTHERN FLORIDA SATURDAY AS MAJOR CATEGORY 3
Latest RECON and Satellite data indicates that Wilma has begun to rapidly intensify -- and there are no obvious
impediments to this process foreseen for the next 36 hours. Only eye-wall replacement cycles - which are
unpredictable - would be an event that terminates the intensification process for about 12 hours.
About 2 hrs ago, the last RECON reported a central pressure of 954mb - a 16mb drop in about 2 hours -- and a
reading normally associated with a CATEGORY 4 hurricane. MAX winds on the outbound leg from the center
had already reached 101Kts in the North quadrant. Satellite imagery has become extremely impressive, with a
well defined eye, and extremely cold (-80°C) cold cloud tops forming a solid CDO centered perfectly above the
storm center. Dvorak satellite estimates would classify this as a
CAT 3. But we will have to wait for the next
RECON late tonight before we will know for sure.
While the 00Z data model runs will not be complete for several more hours -- the 18Z GFS and NOGAPS
output have been closely reviewed. Both models are within the inner 2/3rds of the entire 'model track envelope'.
In addition, I accessed the Navy's real-time altimetry based oceanic temps profiles - and found some very
interesting information regarding the water temps over the far northwest Caribbean and Yucatan Channel.
Because of this information, I decided to issue this update before the 00Z model runs complete. I will send out
a brief update around midnight, after the GFS output becomes available.
The very small, 8NM wide storm center is now located near 16.8N/81.8W - about 175NM South of Grand
Cayman, and is moving WNW at 5Kts. Normally, after such a rapid intensification that results in an eye
diameter of less than 10NM, this is usually followed by an eyewall replacement cycle. If this commences -- the
pressure will cease falling, but it quite possible the wind speeds may still pick up some more to become more in
line with a storm that has such a low pressure reading. In any event, if the re-cycling does begin overnight, it
likely would be complete by noon Wed, and would then allow for another 24 hours in which the storm could
resume a rapid intensification. In addition,m by late Wed and on through Friday, the storm will be passing over
the warmest heat content waters in the entire Atlantic Basin. What I found this evening, using the Navy's
altimetry derived SST's -- is that the water temps on the surface of the ocean are actually a couple of degrees
cooler than just below surface layer!. The mid mid fall temp fall off in water temps begins at the surface of
course, but because it has only just begun, temps are 1-2deg warmer about 10-50 meters below the surface!
This is rather ironic, in that it assures the slow moving storm will at first be upwelling WARMER Water!
Normally, upwelling results in colder, sub-surface water being drawn upwards. Combined with the overall
very favorable outflow, low wind shear environment -- CAT 4 now seems like a very distinct probability.
Once the storm begins it's turn towards the NE and then ENE later Friday -- it will begin to experience
significant wind shears that will cause the storm to begin weakening some. In addition, as it nears the Florida
coastal waters, the sea surface temps cool off rather dramatically. As I have been saying from the beginning, it
seems likely that whatever the ultimate intensity of Wilma is, it will likely make landfall 1 full category weaker.
assuming a CAT 4 hurricane by Friday, which now seems to be a certainty, Wilma would make landfall as
a CAT 3, Major Hurricane.
The model guidance is clear -- showing the envelope of landfall locations from the Florida Keys to Sarasota, on
Saturday. And while the average model errors for track forecasts 5 days out is about +/- 300 miles -- the
consistency and uniform agreement between all the models gives me great confidence that they will verify.
Very similar confidence level we saw with Hurricane Rita -- 4 days out, it still was within 100 miles or so of it's
final landfall point.
The NOGAPS model shows landfall just south of Sarasota - while the GFS is further south, along the
Florida keys and southern Florida -- and emerging off the coast near Ft. Lauderdale. My first guestimate is to
side with the GFS. And in fact, I might as well best describe the track as the reverse instant replay of Katrina's
track -- coming in over the Everglades, crossing Dade County and ending up off the coast near or just north
of Ft Lauderdale.
I will have a brief update later tonight after seeing the 00Z model runs -- and whether or not an eye wall
replacement cycle his showing any signs of actually starting.
Steve Gregory
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Last Visible image of the day, shows the small diameter eye beginning to become visible, with a
hot tower, or over shooting top on the west side of the eyewall, casting a shadow to the east.
This just in color enhanced IR Image shows a well defined eyewall, with the signature worthy of a CAT 4, severe hurricane.
This 85Ghz pass a few hours ago shows a very interesting
feature for a strong hurricane -- relatively 'thin' feeder bands and
convective eyewall. This is due to dry air entrainment --
and there is a lot of it to the northwest of the storm. For
hurricanes that are able to attain this intensity, what this usually means
is that the rainfall totals from such a hurricane are usually not as heavy
as would otherwise be the case.
The storm obviously has good outflow, especially excellent to the east where it now has 2 outflow channels
with one branch turning southward, but the other continuing ENE into a 'mass sink' -- the large upper level
low over the central Atlantic. The outflow to the west is good, but not spectacular.
Wind shear analysis -- shears are under 5kts in the vicinity of the storm, and will remain low for the next 36 hours. But by the time
the storm near the Yucatan, shears -- associated with the WSW winds ahead of the major TROF that will develop over the central U.S.,
will increase dramatically -- and begin the weakening process.
SST's - real-time --show 29°+ surface water temps lie ahead of the storm, but drop off to 27.5°C
along the west coast of Florida.
BUT - the water temps in the upper 50 meters of the ocean are actually 1-2°F warmer than at the surface!
Though the dataset was incomplete, local OBS indicate water temps are around 24°CD at 50Meters below
the surface near the Florida coast.
Purely as an FYI -- SST are still above normal in much of the Gulf, and the water surrounding the Bahamas
and Cuba.
The 18Z model runs were similar, to the full set of 12Z runs -- the consensus track is basically the one used by NHC for their forecast
this evening. My preference is for a track about 50NM further south -- and that would mean much stronger wind for the heavily
populated SE coast of Florida.
In any case -- I would advise all residents in the Florida Keys to prepare for and then begin
evacuting the Keys by Thursday if the forecast track remains unchanged.
Intensity forecast -- from 18Z shows a CAT 3 -- but subsequent reports and observation point to this being too low, and a CAT 4
is becoming increasingly likely.
Last available NHC track forecast. If available, I will post the 11PM, NAVY VERSION
of the track and intensity forecast later tonight with my brief status update.
Most likely, a little after midnight local.