Hurricane Hurricane IDALIA: threat to the northeastern Gulf Coast

[WesL]

Good morning!

WTNT35 KNHC 300923 CCA
TCPAT5

BULLETIN
Hurricane Idalia Advisory Number 15...Corrected
NWS National Hurricane Center Miami FL AL102023
500 AM EDT Wed Aug 30 2023

Corrected storm surge watch changes

...IDALIA RAPIDLY INTENSIFIES INTO A CATEGORY 4 HURRICANE...
...CATASTROPHIC STORM SURGE AND DESTRUCTIVE WINDS ARE NEARING THE
FLORIDA BIG BEND REGION...


SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...29.1N 84.1W
ABOUT 60 MI...95 KM W OF CEDAR KEY FLORIDA
ABOUT 90 MI...145 KM S OF TALLAHASSEE FLORIDA
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...940 MB...27.76 INCHES

 

[UncleJuJu98]

 

[UncleJuJu98]

 

[Casuarina Head]

Tampa Bay was expected to receive 4–7’ of surge. Based on current images and videos the actual surge looks to be notably less. Also, the fact that the inner core is small and the forward speed rapid signifies to me the possibility that the peak surge in the Big Bend may be well below 16’. Finally, current radar indicates a pronounced dry-slot in the eastern semicircle, indicative of dry-air intrusion that is likely limiting not just intensification, but also the transfer of strong winds to the surface. (Incidentally, Ian suffered from the same and ended up producing surprisingly low winds on land, as evidence by in-situ observations, reconnaissance notwithstanding.) In fact the eastern part of the inner core is open: the eye itself is not fully closed off yet. Unless the eastern quadrant fills in and the wind-field expands (both of which could still happen), I think that Ida’s actual impacts are going to be much less severe than expected, both in Tampa Bay and along the Big Bend. Also, just a reminder: Camille and Betsy, each of which was a Category-4+ at landfall, both struck the Gulf Coast during El Niño, and others have too, so Idalia would not be unprecedented in this regard. So even if Idalia were to come in as a Cat-4+, which is still far from guaranteed, it would not be without precedent.

To further up on this: based on data from reconnaissance I think that this is not even close to a 115-knot Category-4, at least at the surface. A sonde in the western part of the core, which has consistently featured the strongest convection, found that 10-m (~33-ft) sustained winds were only 78 knots, while at ~76 m (250 ft) the winds were 114 knots, or ~46% higher. So the surface winds are likely considerably lower than indicated by flight-level winds. Winds in the other quadrants are not likely to be too much higher. Radar indicates a very sloppy presentation, with almost no convection in the eastern semicircle. The fact that the radius of hurricane-force winds remains so small also means that the surge is going to be much lower than forecast. As of now I think that Idalia is closer to a high-end Cat-2 than a low-end Cat-4. The fact that this will be classified as a Cat-4 landfall, in spite of the dearth of evidence, will only lead to complacency in the future. Unfortunately, politicisation of the AGW issue is forcing NOAA’s scientists to be overly lenient in classifying high-end landfalls. (We saw this with Ian last year; very thorough, abundant, land-based observations from the point of landfall did not even support sustained winds of major-hurricane status, much less 130 knots, notwithstanding a very low MSLP in the 940s to low 950s mb.) This is terrible for the reliability of climatological records and for future preparedness. But it’s very convenient for the insurance-providers, whose lobbyists dominate Congress. “Hey, climate change is causing stronger landfalls, so we need to raise rates. If NOAA doesn’t go along, we’ll tell Congress to cut funding or privatise.” Science and the people lose in the end.

 

[Taylor Campbell]

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[WesL]

Congrats on being our 100,000th member post on the new forum!

 

[South AL Wx]

7 am position update: Winds down slightly to 125 mph, pressure up slightly to 947 mb:

Radar and Air Force Reserve Hurricane Hunter aircraft data indicate that an eyewall replacement cycle has begun. Idalia's maximum sustained winds are now estimated near 125 mph (205 km/h) with higher gusts. This change in wind speed does not diminish the threat of catastrophic storm surge and damaging winds.

The estimated minimum pressure indicated by Air Force Reserve Hurricane Hunter aircraft data is 947 mb (27.96 inches).

 

[Clancy]

Extreme Wind Warning now.

BULLETIN - EAS ACTIVATION REQUESTED
Extreme Wind Warning
National Weather Service Tallahassee FL
720 AM EDT Wed Aug 30 2023

The National Weather Service in Tallahassee has issued a

* Extreme Wind Warning for...
Lafayette County in Big Bend Florida...
North central Dixie County in Big Bend Florida...
Northeastern Taylor County in Big Bend Florida...

* Until 1015 AM EDT.

* At 719 AM EDT, National Weather Service Doppler radar and surface
observations indicated extreme winds, associated with the eyewall
of Hurricane Idalia, were moving onshore 15 miles northwest of
Steinhatchee, moving northeast at 18 to 20 mph. THIS IS AN
EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION!

* Locations impacted include...
Mayo, Perry, Cross City, Pinland, Cooks Hammock, Shamrock, Chancey,
Secotan, Boyd, Smith, Buckville, Alton, Mayo Junction, Townsend,
Hines, Foley, Perry-Foley Airport, Bucell Junction, San Pedro
Junction, and Day.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The safest place to be during a major landfalling hurricane is in a
reinforced interior room away from windows. Get under a table or
other piece of sturdy furniture. Use mattresses, blankets or pillows
to cover your head and body. Remain in place through the passage of
these life-threatening conditions.

 

[South AL Wx]

Looking at the TLH radar, looks like she is making landfall now.

 

[akt1985]

It looks like landfall will be at Keaton Beach.

 

[South AL Wx]

Officially made landfall at 7:45 am near Keaton Beach. 125 mph winds, pressure 949 mb.

 

[Clancy]

Google Maps is showing a lot more traffic than I'd want to see within miles of the center of a major hurricane. I hope these are not residents deciding to get on the roads.

 

[Clancy]

It looks as though the eyewall has gotten better defined after landfall?

 

[akt1985]

The extreme wind warning now includes Live Oak and Suwannee County, inland from the coast.

 

[Taylor Campbell]

Very bad tree damage. Multiple very large trees down across roads and impassible. The backside is hitting me now and it’s very strong.

 

[Clancy]

Very bad tree damage. Multiple very large trees down across roads and impassible. The backside is hitting me now and it’s very strong.

Stay safe out there please!

 

[Taylor Campbell]

Wow, this thing is a wind bag. It’s been relentless!

 

[Taylor Campbell]

Stay safe out there please!

Thank you!

 

[Clancy]

Formidable winds and convection on that NW end of the eyewall.

 

[notsoencrypted]

To counter earlier misinformation in this thread: