Cat 4 Hurricane Helene | 140mph 938mb | Landfall Big Bend/Perry

[StretchCT]

11 hours ago, StretchCT said:

Looking at the 18z hurricane model runs.  HRWF had the storm at 963 earlier this evening.  HMON 960.  HAFS A at 972. HAFS B at 969.  

HAFS B takes the storm from 965 at 3z to 942 at 12z.

HAFS A takes the storm from 970 at 3z to 951 at 12z. 

  Reveal hidden contents

 

 

OK it's well past 12z now. So where are we...

We only recently reached the starting point of the HWRF and HMON.  And are nowhere near the intensity of HAFS A and B. 

For 6z runs at 12z, HMON is at 952. HWRF 953. HAFSA 963. HAFSB 957.  So you have to toss the HMON/HWRF and reality is between HAFS A and B.  

HAFS B goes to 952 and 107kts just before landfall.

HAFS A goes to 956 and 88kts  just before landfall.

Has me wondering is it slightly tilted based on the wind info? Easterlies at 400mb, Northerlies 500-850 and Westerlies below 850mb.  

I don't see much shear on the satellite and the soundings (broad storm level) are only 10kts in the 850-250 level. 

 It's coming into Key West and Tampa radars and perhaps it is concentric. Maybe thats what's driving the lack of development as NHC noted. 

Edited September 26 by StretchCT

[StretchCT]

Some ARCHER microwave data from 12z

[MidwestWX]

2 minutes ago, StretchCT said:

OK it's well past 12z now. So where are we...

We only recently reached the starting point of the HWRF and HMON.  And are nowhere near the intensity of HAFS A and B. 

For 6z runs at 12z, HMON is at 952. HWRF 953. HAFSA 963. HAFSB 957.  So you have to toss the HMON/HWRF and reality is between HAFS A and B.  

HAFS B goes to 952 and 107kts just before landfall.

HAFS A goes to 956 and 88kts  just before landfall.

Has me wondering is it slightly tilted based on the wind info? I don't see much shear on the satellite and the soundings are only 10kts in the 850-250 level. 

It's coming into Key West and Tampa radars and perhaps it is concentric. Maybe thats what's driving the lack of development as NHC noted. 

Great post as always! My post isn't exactly a direct reply but more of a jumping in point for me.

 

I may not be a tropical meteorologist by trade but I have studied the subject.

Hurricane models should struggle to resolve landfall intensity given/location given her size. That's also what's likely limiting her wind speeds from being a high end major (that others have brought up). I joked with my coworkers that if she's in the mid 960s by the time I wake up today, it'll likely hit around 950mb give or take a few MB. Unfortunately she's aob the mid 960s. Its been an rather unique RI case since yesterday afternoon. Her size and speed alone will result in unfortunately significant surge.

[1816]

Helene should be a legendary hurricane but seems to have a major Achilles heel. For whatever reason, this storm was absent the day they taught eye/eyewall/core formation at hurricane school.  Honestly it's for the best with regards to our coastal Floridian friends. 

As far as inland goes, it's not gonna matter too much. Its gonna be a catastrophe. 

[StretchCT]

14 minutes ago, StretchCT said:

Has me wondering is it slightly tilted

ADT lost the center

4 minutes ago, MidwestWX said:

That's also what's likely limiting her wind speeds from being a high end major

Do our higher end major hurricanes start off smaller?  

[StretchCT]

Dropsonde data so far.  The 128mph wind was at 915mb or 1900 feet or so. I wonder if they keep the 960mb or bump it up to 962.

[NWOhioChaser]

8 minutes ago, 1816 said:

Helene should be a legendary hurricane but seems to have a major Achilles heel. For whatever reason, this storm was absent the day they taught eye/eyewall/core formation at hurricane school.  Honestly it's for the best with regards to our coastal Floridian friends. 

As far as inland goes, it's not gonna matter too much. Its gonna be a catastrophe. 

Yup, non-hurricane related threats are already ongoing inland. An approaching Cat. 2 tonight with a wind field like that is spelling trouble. Not to mention how much water this is will be pushing towards the coast. 
 

Lightning in the outer eyeball suggests some sort of strengthening might be currently present. 
 

 

[Undertakerson2.0]

1 hour ago, thebigo said:

CAt 3 - Surely

[StretchCT]

11am disco notes: Eyewall is almost completely closed. Eye is gradually clearing out. Some reports of TS force winds already in FL. Storm is speeding up. Significant intensification is expected.Depends on how the inner core develops. HWRF/HMON have it as a cat 4.  Helene is at the upward bound compared to other GOM storms. 

Spoiler

Hurricane Helene Discussion Number  13
NWS National Hurricane Center Miami FL       AL092024
1000 AM CDT Thu Sep 26 2024

Helene is gaining strength as it approaches the Florida Big Bend. A 
large eye has become apparent in satellite images, and that feature 
has been gradually clearing out over the past few hours. Convective 
banding is wrapping around the eye, and recent microwave images and 
reports from the NOAA and Air Force Hurricane Hunter aircraft 
indicate than an eyewall is almost completely closed.  The minimum 
pressure has been dropping steadily to near 960 mb, and based on the 
aircraft flight-level wind data, the initial intensity is estimated 
to have increased to 90 kt.  There have been several reports of 
tropical-storm-force winds occurring in portions of South Florida 
and the Florida Keys during the past few hours.

The large hurricane is picking up speed and has turned slightly to
the north-northeast.  The latest initial motion is 025/12 kt.  A
notably faster north-northeastward motion is expected through
landfall, which is expected to occur in the Florida Big Bend region
this evening.  After Helene moves inland, it is forecast to track
over Georgia and then slow down or stall over the Tennessee Valley
when it merges with a mid- to upper-level low pressure system.  Only
minor changes were made to the previous NHC track forecast.

Significant intensification is expected until Helene reaches the
coast since the overall atmospheric and oceanic conditions will
remain conducive.  The amount of strengthening will likely depend on
how much the inner core can contract and consolidate.  The HWRF and
HMON models show significant strengthening to category 4 status,
while most of the other models are a little lower.  The main message
is that Helene will likely make landfall as a large major hurricane
in the Florida Big Bend this evening, and all preparations in the
hurricane warning area should be rushed to completion.

It should also be re-emphasized that Helene is a very large
hurricane.  In fact, comparing the system with previous hurricanes
in the Gulf of Mexico over the past couple of decades, Helene is at
the upper bound in terms of size. As a result, storm surge, wind,
and rainfall impacts will extend far away from the center and well
outside the forecast cone, particularly on the east side.  In
addition, the fast forward speed when Helene moves inland will
result in a far inland penetration of strong winds over parts of the
southeastern United States, including strong gusts over higher
terrain of the southern Appalachians.  Accordingly, a
higher-than-normal gust factor is indicated in the official forecast
while Helene is inland.


KEY MESSAGES:

1. A catastrophic and deadly storm surge is likely along portions
of the Florida Big Bend coast, where inundation could reach as high
as 20 feet above ground level, along with destructive waves.  There
is also a danger of life-threatening storm surge along the remainder
of the west coast of the Florida Peninsula.  Residents in those
areas should follow advice given by local officials and evacuate if
told to do so.

2. Potentially catastrophic hurricane-force winds are expected
within the eyewall of Helene when it makes landfall in the Florida
Big Bend region this evening.  Preparations to protect life and
property should be rushed to completion.  Damaging and
life-threatening hurricane-force winds, especially in gusts, will
penetrate well inland over portions of northern Florida and southern
Georgia later today and tonight where Hurricane Warnings are in
effect.  Strong wind gusts are also likely farther north across
portions of northern Georgia and the Carolinas, particularly over
the higher terrain of the southern Appalachians.

3. Catastrophic and life-threatening flash and urban flooding,
including numerous significant landslides, is expected across
portions of the southern Appalachians through Friday. Considerable
to locally catastrophic flash and urban flooding is likely for
northwestern and northern Florida and the Southeast through Friday.
Widespread significant river flooding and isolated major river
flooding are likely.


FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 25.5N  85.5W   90 KT 105 MPH
 12H  27/0000Z 28.8N  84.3W  105 KT 120 MPH
 24H  27/1200Z 33.9N  84.5W   55 KT  65 MPH...INLAND
 36H  28/0000Z 36.4N  86.6W   30 KT  35 MPH...POST-TROP/EXTRATROP
 48H  28/1200Z 36.5N  87.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 60H  29/0000Z 36.3N  87.6W   20 KT  25 MPH...POST-TROP/EXTRATROP
 72H  29/1200Z 36.2N  87.2W   20 KT  25 MPH...POST-TROP/EXTRATROP
 96H  30/1200Z...DISSIPATED

$$
Forecaster Cangialosi

There could be strengthening between 12 and 24 hours. 

INIT  26/1500Z 25.5N  85.5W   90 KT 105 MPH
 12H  27/0000Z 28.8N  84.3W  105 KT 120 MPH
 24H  27/1200Z 33.9N  84.5W   55 KT  65 MPH...INLAND
 36H  28/0000Z 36.4N  86.6W   30 KT  35 MPH...POST-TROP/EXTRATROP
 48H  28/1200Z 36.5N  87.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 60H  29/0000Z 36.3N  87.6W   20 KT  25 MPH...POST-TROP/EXTRATROP
 72H  29/1200Z 36.2N  87.2W   20 KT  25 MPH...POST-TROP/EXTRATROP
 96H  30/1200Z...DISSIPATED

Edited September 26 by StretchCT

[Undertakerson2.0]

Edited September 26 by Undertakerson2.0

[StretchCT]

4 minutes ago, StretchCT said:

Some reports of TS force winds already in FL

[Undertakerson2.0]

5 minutes ago, StretchCT said:

Yep - NHC mentioned that in the 11am update

ata, the initial intensity is estimated to have increased to 90 kt. There have been several reports of tropical-storm-force winds occurring in portions of South Florida and the Florida Keys during the past few hours.

[Jpfalcon]

Race against the clock now regarding RI. Hopefully she falls short of Cat 4, but don't think it's really going to matter given the storm surge and inland flooding impacts.

[StretchCT]

Nearly all these readings are 80mph+ flight level winds. It goes on for 90 miles to the east. 

And the furthest east flight level wind is 101mph. That's 120 miles from the center. 

The dropsonde there only has 53 mph at surface, but 115mph at 780 mph. 

[Undertakerson2.0]

3 minutes ago, Jpfalcon said:

Race against the clock now regarding RI. Hopefully she falls short of Cat 4, but don't think it's really going to matter given the storm surge and inland flooding impacts.

Concur - the number is pretty much for weenie study now. The die is cast for severity and level of impact

[1816]

Not to mention last minute shifts with the track once it moves inland could make a huge difference. That's one thing we need to watch. Tornados, wind damage, power outages and of course flooding - where does the worst of it go. 

I wouldn't want to be anywhere in the Carolinas or Georgia but particularly the upstate mountainous areas look to get the worst of it and there are a whole lot of people in Atlanta and Charlotte who should be paying close attention.  

[Undertakerson2.0]

It's a three, I tell ya. They just aren't saying so ATM

[Sentinel]

10 minutes ago, Undertakerson2.0 said:

It's a three, I tell ya. They just aren't saying so ATM

GFS has been slowing this down about 6-12 hours as it approaches big bend. This could be quite historic. 

[Burr]

Ya.  It’s looking lopsided but firing

 

[Sentinel]

3 minutes ago, Burr said:

Ya.  It’s looking lopsided but firing

 

Latest Vortex Message has an eye of 30 NM.. CLOSED. 

[Sentinel]

BTW - Nice to see everyone coming out! I hope everyone is doing well!

[Jpfalcon]

If the inner eyewall can close off within the next few hours it'll be game on.

[Sentinel]

1 minute ago, Jpfalcon said:

If the inner eyewall can close off within the next few hours it'll be game on.

As long as it can mix -and keep- the dry air out of the core. Dry air is the only thing keeping this in check right now, that I -and others- have seen. 

[StretchCT]

Radar overlay  - west side is out of range

[Undertakerson2.0]

Stretch, what is the lightning map looking like?

6 minutes ago, Sentinel said:

BTW - Nice to see everyone coming out! I hope everyone is doing well!

Indeed. 

Doing well here, despite so many people "out there" really sucking so much. LOL (j/k, kinda)