ATL: HELENE - Post-Tropical - Discussion

[Hypercane_Kyle]

Recon data supports Category 4, 115-120 knots based on flight level winds of ~135 knots.

Another historic Gulf major hurricane.

[Beef Stew]

Uh, did NHC just lower the intensity of a rapidly intensifying major hurricane mere hours from landfall?

To be fair, they have more data than us, so I'm sure there's a good reason. That, or they just made a typo

Have they even sampled the eastern side yet?

This has to be a typo

089
WTNT64 KNHC 262200
TCUAT4

Hurricane Helene Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL092024
600 PM EDT Thu Sep 26 2024

...HELENE CONTINUES HEADING FOR THE FLORIDA BIG BEND...
...TROPICAL STORM CONDITIONS SPREADING NORTHWARD ALONG THE WEST
COAST OF FLORIDA...

A slightly elevated Weatherflow station at the Skyway Fishing Pier
near the entrance to Tampa Bay recently measured a sustained wind
of 50 mph (80 km/h) and a gust to 69 mph (111 km/h).

SUMMARY OF 600 PM EDT...2200 UTC...INFORMATION
----------------------------------------------
LOCATION...28.0N 84.5W
ABOUT 115 MI...185 KM W OF TAMPA FLORIDA
ABOUT 210 MI...335 KM SW OF TALLAHASSEE FLORIDA
MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

$$
Forecaster Bucci

I think it will get bumped to 130 momentarily. I'm assuming it was a typo?

[weeniepatrol]

[NDG]

NHC prematurely dropped it from 125 mph down to 120 mph before the NOAA recon passing the eastern quadrant.
And TV mets jumped on their wagon as well.

[HurricaneAndre2008]

https://www.tropicaltidbits.com/recon/r ... HELENE.png

[Teban54]

Uh, did NHC just lower the intensity of a rapidly intensifying major hurricane mere hours from landfall?

To be fair, they have more data than us, so I'm sure there's a good reason. That, or they just made a typo

Have they even sampled the eastern side yet?

This has to be a typo

089
WTNT64 KNHC 262200
TCUAT4

Hurricane Helene Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL092024
600 PM EDT Thu Sep 26 2024

...HELENE CONTINUES HEADING FOR THE FLORIDA BIG BEND...
...TROPICAL STORM CONDITIONS SPREADING NORTHWARD ALONG THE WEST
COAST OF FLORIDA...

A slightly elevated Weatherflow station at the Skyway Fishing Pier
near the entrance to Tampa Bay recently measured a sustained wind
of 50 mph (80 km/h) and a gust to 69 mph (111 km/h).

SUMMARY OF 600 PM EDT...2200 UTC...INFORMATION
----------------------------------------------
LOCATION...28.0N 84.5W
ABOUT 115 MI...185 KM W OF TAMPA FLORIDA
ABOUT 210 MI...335 KM SW OF TALLAHASSEE FLORIDA
MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

$$
Forecaster Bucci

It has just been corrected moments ago, though they will likely need to make another update anyway for Cat 4 strength.

000
WTNT64 KNHC 262205 CCA
TCUAT4

Hurricane Helene Tropical Cyclone Update...Corrected
NWS National Hurricane Center Miami FL AL092024
600 PM EDT Thu Sep 26 2024

Corrected for the maximum winds and forward motion

...HELENE CONTINUES HEADING FOR THE FLORIDA BIG BEND...
...TROPICAL STORM CONDITIONS SPREADING NORTHWARD ALONG THE WEST
COAST OF FLORIDA...

A slightly elevated Weatherflow station at the Skyway Fishing Pier
near the entrance to Tampa Bay recently measured a sustained wind
of 50 mph (80 km/h) and a gust to 69 mph (111 km/h).

SUMMARY OF 600 PM EDT...2200 UTC...INFORMATION
----------------------------------------------
LOCATION...28.0N 84.5W
ABOUT 115 MI...185 KM W OF TAMPA FLORIDA
ABOUT 210 MI...335 KM SW OF TALLAHASSEE FLORIDA
MAXIMUM SUSTAINED WINDS...125 MPH...205 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 23 MPH...37 KM/H
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

$$
Forecaster Bucci

[Beef Stew]

NHC prematurely dropped it from 125 mph down to 120 mph before the NOAA recon passing the eastern quadrant.
And TV mets jumped on their wagon as well.

It's back up to 125 now.

[ColdMiser123]

Standard conversion of flight level wind of 136 kt gets you 122 kt at the surface - but may be a bit higher than that for Helene since the undersampling factor will be a bit higher for a larger storm. So 120-125 kt seems reasonable.

[Kazmit]

Special advisory coming soon?

[ConvergenceZone]

Uh, did NHC just lower the intensity of a rapidly intensifying major hurricane mere hours from landfall?

Hmm, that does sound odd. I wonder if it's a typo

[Beef Stew]

Based on that last pass, I think an intensity of 120kts/140 mph could be justified. 125 kts/ 145 mph is a possibility as well.

Edit: I didn't realize this was the NOAA plane and not AF. In that case, 115-120 is the best estimate IMO, but I'd lean towards 120 due to potential undersampling of a large storm and the rate of current intensification.

[kevin]

Based on the 947 mb dropsonde and the 136 kt FL I say we have our 120 - 125 kt cat 4. Who knows what it's gonna do in its final hours before landfall. A high-end cat 4 or maybe even more is in play with its current intensification rate.

[Category5Kaiju]

I'm expecting an upgrade to Category 4 fairly soon; very dangerous situation for the Panhandle/Big Bend, including Tallahassee

[zzzh]

Standard conversion of flight level wind of 136 kt gets you 122 kt at the surface - but may be a bit higher than that for Helene since the undersampling factor will be a bit higher for a larger storm. So 120-125 kt seems reasonable.

This is at 750mb so conversion is around 0.86, not 0.9.

[TallyTracker]

Special advisory coming soon?

I doubt they will go that far. This is what they have been forecasting. If they think it will hit Cat 5, perhaps that will change.

[WaveBreaking]

[CrazyC83]

Given the elevation of the NOAA plane, 115 kt seems most reasonable.

[Travorum]

Uh, did NHC just lower the intensity of a rapidly intensifying major hurricane mere hours from landfall?

To be fair, they have more data than us, so I'm sure there's a good reason. That, or they just made a typo

Have they even sampled the eastern side yet?

This has to be a typo

089
WTNT64 KNHC 262200
TCUAT4

Hurricane Helene Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL092024
600 PM EDT Thu Sep 26 2024

...HELENE CONTINUES HEADING FOR THE FLORIDA BIG BEND...
...TROPICAL STORM CONDITIONS SPREADING NORTHWARD ALONG THE WEST
COAST OF FLORIDA...

A slightly elevated Weatherflow station at the Skyway Fishing Pier
near the entrance to Tampa Bay recently measured a sustained wind
of 50 mph (80 km/h) and a gust to 69 mph (111 km/h).

SUMMARY OF 600 PM EDT...2200 UTC...INFORMATION
----------------------------------------------
LOCATION...28.0N 84.5W
ABOUT 115 MI...185 KM W OF TAMPA FLORIDA
ABOUT 210 MI...335 KM SW OF TALLAHASSEE FLORIDA
MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

$$
Forecaster Bucci

This almost immediately did not age well, recon has some sort of supernatural ability to sample the peak winds 5 minutes after the NHC posts an advisory.

[Hypercane_Kyle]

There's a chance a stadium effect might be getting ready to go on display. Still obscured, but once those cloud temps warm...

The amount this storm has improved on satellite in just the last hour is insane.

[Teban54]

Special advisory coming soon?

I doubt they will go that far. This is what they have been forecasting. If they think it will hit Cat 5, perhaps that will change.

NHC generally does make immediate special advisories when there are major changes in current strength, regardless of forecasts.