SEPT 22, 2005 / 4:33 PM CDT
RITA STABILIZES AS VERY DANGEROUS CAT 4 HURRICANE
STORM MOVING NORTHWESTWARD -- LANDFALL THREAT
PORT ARTHUR AT GREATEST RISK OF LANDFALL IN 44 HOURS
SEVERE FLASH FLOOD THREAT THROUGH MONDAY
The eye wall replacement cycle that began this morning is nearing completion, as evidenced by
the improved satellite imagery signature and the latest RECON reports. The central pressure
that had risen to 915mb this morning, is now falling off gradually to 913mb, while the thermal
eye wall temp differential that had risen to 4°C this AM, has risen to 7°C as of 2:50PM CDT.
MAX sustained winds were earlier reported at 122Kts (130mph sustained surface) which is a
CAT 4 intensity -- but in the past hour, have increased to 133Kts in the NW quadrant. It is
safe to assume winds are currently around 140Kts in the NE quadrant, or 145mph near
the surface -- a very strong CAT 4 intensity. The height of the 700mb surface has fallen 10 meters
in the last few hours, to 2329 meters.
The storm is now located near 25.8N/89.5W or 390NM SE of Port Arthur. The storm is now
moving NW (305°) at 9Kts based on the last 3 hours of fixes. The crew continues to report a
double eyewall with a diameter of 18NM and 48NM -- but the thermal and pressure trends, along
with the improved colder CDO signature -- tend to indicate the eye wall recycling is either completed,
or has simply stabilized for now.
The latest 18Z models, including the late , full cycle 12Z run and GFS Ensemble forecast, are
in extreme agreement with a landfall very near Port Arthur around 1PM CDT on Saturday.
The GFS and NOGAPS are to the right of this landfall envelope, showing the storm crossing
the coast right along the LA/TX state line. The models are also in agreement that the storm has peaked
in intensity, and will gradually weaken on it's way to the coast -- making landfall as a very strong
CAT 3 or low end CAT 4. Intensity forecasts are extremely unreliable in general -- as evidenced by
the extraordinary deepening of the storm yesterday. That said -- I believe we will see RITA regain
CAT 5 intensity tonight, and then begin a slow weakening during the final 24 hours before
landfall -- which will come as a CAT 4.
However, because of RITA's extreme pressure and prolonged period over the Gulf as a CAT 5 storm, the
storm surge will be equal to that of CAT 5 hurricane. A tidal surge of 20-22 feet, with Port Arthur
most vulnerable to catastrophic storm surge damage -- will likely cover a 20-30 mile stretch of coast
from the point of landfall eastward, with 13-18 ft extending to 50-80 miles east of the point of landfall.
Gale force winds extend out for over 200 miles from the center -- and gusts to gale force will reach
over to the New Orleans area. A tidal storm surge of 4-8 feet will hit the Mississippi Delta region
over to Grand Isle, LA.
Of growing concern post landfall is the path of the storm after it makes landfall Saturday. All the
global models are forecasting Rita to slow down and become quasi stationary by late Saturday night
somewhere along the TX/LA border about 100-150 miles inland. This occurs in response to the
rebuilding of a ridge to the north of the storm over the central U.S.. The ridge then continues to
expand towards the east and southeast, and is expected to turn Rita towards the southwest later
Sunday and into Monday. In the process, and although the winds will calm down -- the storm will
likely bring over 48 hours of torrential rainfall to much of Louisiana on southwestward towards the
Houston area - after the storm comes inland. This greatly raises the chances of severe flash flooding
over inland areas on Sunday and Monday -- with rainfall totals easily exceeding 25" in some locations
- with 30" or more quite possible in some isolated locations.
A Storm Surge and Wind Forecast forecast Graphic will be sent out, along with a brief update on the storm itself
around 8PM CDT. A full forecast package will be sent around 11:30 tonight after all the 00Z global model arrives.
Steve Gregory
WeatherInsite
wunderground.com |
