SEPT 23 , 2005 / 12 :05 AM CDT
VERY DANGEROUS CATEGORY 4 HURRICANE TO HIT PORT ARTHUR
CATASTROPHIC DAMAGE LIKELY NEAR AND UP TO 30 MILES EAST OF LANDFALL POINT
STORM WINDS EXPAND WHILE INNER MAX WINDS EASE OFF - FOR NOW
GALE FORCE WIND GUSTS ALREADY ALONG SOUTH COAST OF LOUISIANA
AND THE STORM AFTER THE STORM....
The latest model run data continue to call for a landfall near Port Arthur Texas around Noon Saturday.
The latest RECON and satellite data locate the storm near 26.2N/90.3W or about 345NM SE of both
Port Arthur, and Galveston Texas. MAX Sustained surface winds are near 130mph, with gusts to 150mph --
and the central pressure has risen a bit to 917mb. Gale force winds now extend up to 220 miles away from
the center in the northern semi-circle, and about 150 miles to the south and southwest. The buoy located about
60 miles south of the hurricane recently reported southerly wind gusts to 114mph.
ANALYSIS OF STORM STRUCTURE
The eye wall replacement cycle that began this morning, and coincided with storm moving away from the very
warm loop current and over a smaller area of slightly cooler sea surface temps -- led to a weakening of the storm
during the day. By late afternoon, it appeared that the eye wall replacement was nearing completion as the pressure
began to fall again (from 915mb to 911mb), and the CDO became colder and more pronounced. The thermal
eyewall temp differential fell as low as 4°C, but then began increasing again to around 10 °C -- and it appeared
that the inner eyewall was about ready to collapse completely -- allowing the outer ring of convection to contract
inward to replace the inner wall.
However -- shortly after 6PM, the storm's eye wall replacement cycle suddenly became 'arrested' -- and until
the past hour, the storm maintained a double eye wall structure, cloud tops began to warm, and the thermal eye wall
differential began to decrease again as the pressure rose slowly. However, at the same time, the size of the storm
expanded as the inner most pressure gradient relaxed, but the central pressure remained extremely low. The result
was a broadening of the gale force winds. On the latest satellite imagery loop --you can see the coldest convective
cloud tops (RED's) first warm and and were located far from the storm center - while in the past 2 hours, the
cold tops have again begun to increase (stronger convection) and contract back towards the inner core of the storm.
The RECON Reports (decoded form for novices) indicates that the inner, 18NM wide eyewall may finally
be fully collapsing while the outer ring that was 48NM across and is now 32NM across -- is likely to become
the primary eyewall during the next 3-6 hours. This will also coincide with the normal diurnal Maximum
in convective activity - and, the storm will again be moving over a deeper warm water pool of water. While
intensity forecasts have almost no real skill in the short term -- there appears to be a reasonable basis to forecast
the storm to re-intensify by about 10mb, and see the winds return to near or minimal, CAT 5 intensity during the
next 8-16 hours.
A couple folks have asked, after looking at the wind shear charts from one of the WEB sites, how come the storm
has not weakened more since the wind shear charts show 10-15Kts of shear above the storm. The truth of the matter
is the wind shear analysis is bogus! The computer based analysis scheme is not properly resolving the wind vectors
associated with the storm's outflow and the surrounding environmental wind shears. If there really was 10-15 kts of
wind shear -- this storm would be weakening as fast as it intensified yesterday! This is a great example of putting too much
faith in the automated analysis products and by inference, the model forecasts. Garbage in, garbage out. While it has become
extremely easy to become an 'armchair forecaster' with all the automated products available from the WEB -- the models
are not perfect -- and it takes almost as much experience to properly interpret the output data from these models as
it once took to become a 'good forecaster' 40 years ago when there was next to no such thing as a computer based product.
CURRENT OBSERVED CONDITIONS
The effects from Rita are already reaching into the north central Gulf - wind gusts to gale force have reached to
just off shore Alabama and Louisiana, with outer rain squalls already passing across the outer coastal areas of Louisiana
The buoy 65 miles south of Dauphin Island is reporting wind gusts to 46mph, and sea swells of 22 ft. Grand Isle
has wind gusts to 49mph and 9 ft seas; South Timber Block just offshore from Grand Isle is reporting wind gusts to 57mph,
while Marsh Island just off the coast from Vermillion Bay, has winds to 35mph.
Tides are running 2-3 feet above normal across all of the southern coast of Louisiana, with 10-15 ft swells beginning
to reach the offshore platforms and buoys between Port Arthur and Galveston. All this with 36 hours to go before
the storm even reaches the coast.
FINAL 24 HOURS
By tomorrow afternoon -- the latest global models are forecasting the weakening of the outflow channel to the west of the storm and
increased shear -- and this MAY allow for significant, albeit slow, weakening of the storm. I say MAY - because as noted above, the
computer analysis of the current wind field (the ';initialization' data) was simply not correct in some areas surrounding the storm
itself. That said, the models did overall verify and then initialize the model datasets very well, and there is high confidence in the forecast
track of the storm. While the surface water temps are very warm along the coast and offshore for 100 miles, the depth of the warm water
is very shallow. The slower the storm moves in the final 12-18 hours before landfall, the more likely it is to extract much of the latent heat
energy in the top layer of the ocean, and to also upwell the cooler water residing just below the surface. That would lead to a significant
weakening of the storm's MAX winds. But by then, it basically is too late to make much of a difference in the enormous scope and
level of the storm surge. Even if Rita weakens to a CAT 3 Hurricane -- the storm surge will be similar to a 'typical' CAT 5 hurricane.
POST LANDFALL FLOOD THREAT -- AND MORE BAD NEWS?
Earlier today - I brought up the issue of growing concern regarding the potentially massive and deadly flash flooding that will
result from the storm slowing down and then becoming quasi-stationary shortly after going inland. This will lead to a 48
hour period of torrential rainfall from the remnants of the storm that will end up remaining over Louisiana and the upper
Texas coastal Plain. Rainfall totals of 25" are quite possible between Saturday and Monday - after the storm has gone inland.
The latest GFS model run continues to show this slowing of the storm and then going stationary about 100 miles north of the coast
by Saturday night and early Sunday as the high pressure ridge to the north of the storm becomes stronger and blocks the
storm from moving northward. A new, and highly speculative event is the Gas's newest forecast for the storm center which is
shown going stationary at first by late Saturday night is then forecasting the system to turn around and head southward back over
the Gulf of Mexico on Monday, and ending up about 100 miles east of Brownsville Tuesday morning. It also depicts the storm
re-intensifying later Monday and Tuesday.
The next update will Friday morning.
Steve Gregory
WeatherInsite
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PIX 1 - Color enhanced IR Image shows the colder tops associated with the stronger, outer eyewall
convective ring. The deep toned reds have been increasing again in coverage,. and are contracting
back towards the storm center.
PIX 2 New Orleans radar already depicting the outer most heavy squalls that have been hitting
the coast this evening.
The 50 meter water temperature analysis shows the storm has been, and is still over the somewhat cooler
non loop current water, but will be moving over the pool of very high heat content water to the northwest of
it during Friday. This is the period when the storm may in act re-intensify to a CAT 5 storm.
The new 00Z model forecast dataare tightly clustered just west of Port Arthur, while the GFS (not shown) forecasts the
storm to reach Port Arthur around 1PM Saturday. Notice above, the NOGAPS and AVN (both global based models)
are showing the same 'turn around' the GFS is -- bring the storm back southwestward towards southern Texas, but over water.
The GFS is more 'aggressive' in tracking the system further off the coast during the same time period.
Storm Surge forecast I issued earlier this evening remains unchanged -- though the tidal heights will probably end up being
higher over past of SE Louisiana.
The official Navy/NHC forecast brings the storm to just west of Port Arthur Sat morning, a little faster than I expect, but
they also do not indicate any type of slowing or looping of the storm through the period. NHC is forecasting a bit of increase
in winds for Friday, and is reasonable, though I think we all are wondering if the burst of intensification may be stronger than
reflected in their public forecast.