[H] HURRICANE HELENE - Discussion & Aftermath

It also looks like they took the “major” designation back off before landfall. That’s good news.

If you read the discussion, they continue to forecast this to be a "Major Hurricane". It is just the way each forecast point is shown every 12 hours that you do not see it.

Edit: The hurricane is inland on the 8:00PM Thursday position.

It is still projected to reach major hurricane status between the 60 hour and 72 hour forecast. The 72 hour position is inland so you do not see it. Read below.


967

WTNT44 KNHC 240239
TCDAT4
Potential Tropical Cyclone Nine Discussion Number 3
NWS National Hurricane Center Miami FL AL092024
1100 PM EDT Mon Sep 23 2024

Satellite imagery indicates that there has been little change in
the organization of the system since earlier today. Most of the
deep convection is over the eastern part of the broad circulation.
Animation of proxy-vis GOES images, and radar observations from
Grand Cayman Weather Service suggest that the disturbance still
does not have a well-defined center of circulation, so the system is
kept as a potential tropical cyclone for the time being. The
advisory intensity is held at 30 kt which is in agreement with a
Dvorak estimate from TAFB. An Air Force reconnaissance aircraft is
scheduled to investigate the area in a few hours to provide a
better description of the system's structure along with an updated
intensity estimate.

The initial motion estimate is a rather uncertain 330/5 kt. During
the next day or so, the disturbance is expected to turn
northwestward along the southern and southwestern side of a
mid-level high pressure area. Then, the high is expected to shift
eastward while a mid-level trough drops into the central United
States. This evolution of the steering pattern should cause the
system to accelerate northward to north-northeastward over the
eastern Gulf of Mexico and toward the northeastern Gulf Coast
through Thursday. There is good agreement in the track guidance, and
the official forecast is close to the corrected dynamical consensus
model, HCCA, prediction. This is also very similar to the previous
NHC forecast.

An upper-level low over the northeastern Yucatan Peninsula has been
imparting some southwesterly vertical wind shear over the
disturbance. This has probably caused a temporary disruption in
development. Dynamical guidance shows this low weakening with time,
resulting in a reduction of shear in an environment that is
otherwise very conducive for intensification. The system is
projected to move over waters of very high ocean heat content,
which should lead to considerable strengthening during the forecast
period. The official intensity forecast is similar to the previous
one and lies between the statistical-dynamical model guidance and
the purely dynamical model predictions. It should be noted that
the 72-hour forecast allows for a little weakening after moving
inland, so the cyclone is still expected to be at major hurricane
strength at landfall.

It should also be noted that the cyclone is expected to grow in
size while it traverses the Gulf. Thus, the storm surge, wind, and
rainfall impacts will extend well away from the center, particularly
to the east of the system. In addition, the fast forward speed
while it crosses the coast will likely result in farther inland
penetration of strong winds over parts of the southeastern United
States after landfall.

KEY MESSAGES:

1. The disturbance is forecast to intensify and be near hurricane
strength when it reaches the far northwestern Caribbean Sea Tuesday
night. Tropical storm conditions are expected over portions of
western Cuba and the northeastern coast of the Yucatan Peninsula
with hurricane conditions possible.

2. The system is expected to intensify into a major hurricane
before it approaches the northeastern Gulf Coast on Thursday. While
it is too soon to pinpoint the exact location and magnitude of
impacts, the potential for life-threatening storm surge and
damaging hurricane-force winds along the coast of the Florida
Panhandle and the Florida west coast is increasing. Hurricane
Watches and additional Storm Surge watches will likely be issued
for a portion of that area Tuesday morning, and residents should
ensure they have their hurricane plan in place.

3. Potential Tropical Cyclone Nine will bring heavy rain to portions
of the western Caribbean, which will cause considerable flooding
and mudslides across western Cuba. Heavy rainfall will likely
result in locally considerable flash and urban flooding across
portions of Florida, with isolated flash and urban flooding
possible across the Southeast, Southern Appalachians, and the
Tennessee Valley Wednesday through Friday. Minor to isolated
moderate river flooding will be possible.

FORECAST POSITIONS AND MAX WINDS

INIT 24/0300Z 18.4N 82.4W 30 KT 35 MPH...POTENTIAL TROP CYCLONE
12H 24/1200Z 19.1N 83.5W 35 KT 40 MPH...TROPICAL CYCLONE
24H 25/0000Z 20.2N 84.6W 45 KT 50 MPH
36H 25/1200Z 21.6N 85.6W 60 KT 70 MPH
48H 26/0000Z 23.4N 85.8W 75 KT 85 MPH
60H 26/1200Z 26.2N 84.9W 90 KT 105 MPH
72H 27/0000Z 30.4N 83.9W 95 KT 110 MPH...INLAND
96H 28/0000Z 37.0N 85.0W 15 KT 15 MPH...POST-TROPICAL
120H 29/0000Z...DISSIPATED

GFS has it hitting about the same location at about the same intensity.

Anxiously awaiting the 5am update. I’m kind of tired of these big bend storms. We’ve been getting hammered these last few years. Sorry, nothing helpful to add…just venting I guess.

Agree Zack. Seeing that "M" for Major (Category 3) at or prior to landfall is impactful in some folks planning. This may determine whether they make a decision to evacuate or not. It definitely makes for communication problems. You will now have some folks waking up and looking at the map and say to themselves... oh, they increased their forecast back to a major when in actuality that never changed.

No worries. Anyone not reading the fine details of the NHC discussion would think the same thing. Only us weather nerds probably read the discussions anyway.