Major Hurricane Helene

[Radtechwxman]

NHC now forecasting a cat 4 landfall so guess that answers my question of dry air concerns. Ha

[yoda]

Hurricane Helene Discussion Number  10
NWS National Hurricane Center Miami FL       AL092024
400 PM CDT Wed Sep 25 2024

A ragged eye is becoming apparent in visible satellite imagery and
has also been observed in recent radar data from Cancun and western
Cuba.  Based on the improved structure, the initial intensity is
set at 75 kt, which is at the high end of the satellite intensity
estimates.  This is also supported by the earlier Air Force Reserve
reconnaissance mission, which measured a peak 700-mb flight-level
wind of 81 kt.

Helene has turned northward (355/9 kt) and is expected to
accelerate toward the north or north-northeast during the next
24-36 hours as it moves across the Gulf of Mexico and crosses the
Florida Big Bend coast Thursday evening.  After landfall, the
system is forecast to interact with a deep-layer trough to the west
and turn northwestward with a decrease in speed over the Tennessee
Valley.

The environment appears primed for significant strengthening while
Helene moves across the Gulf of Mexico.  The forecast track more or
less runs along the axis of the Loop Current during the next 24
hours, where ocean temperatures are about 30 degrees Celsius.  In
addition, Helene will be moving through an environment of low
vertical shear and strong upper-level divergence.  Some of the
Rapid Intensification (RI) indices, particular DTOPS, respond to
this environment by indicating at least a 90 percent chance of a
35-kt increase in intensity over the next 24 hours.  The NHC
intensity forecast now shows an intensity of 115 kt (Category 4) at
24 hours, which is mirrored by several of the regional hurricane
models and the SHIPS guidance.  It should be noted that additional
strengthening is possible beyond 24 hours before Helene makes
landfall Thursday evening.

Helene is forecast to be a large major hurricane when it reaches the
Big Bend coast of Florida.   As a result, storm surge, wind, and
rainfall impacts will extend well away from the center and 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.  A higher-than-normal gust factor has been
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 late Thursday.  Preparations to protect life and
property should be completed by early Thursday before tropical
storm conditions arrive.  Damaging and life-threatening
hurricane-force winds, especially in gusts, will penetrate well
inland over portions of northern Florida and southern Georgia late
Thursday and Thursday night 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 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 minor to
moderate river flooding is likely, and isolated major river flooding
is possible.

4. Hurricane and tropical storm conditions are expected over
northeastern portions of the Yucatan Peninsula of Mexico this
evening where Tropical Storm and Hurricane Warnings are in effect.
Tropical storm conditions are occurring over portions of western
Cuba within the Tropical Storm Warning area, and hurricane
conditions are possible this evening within the Hurricane Watch
area. Helene will bring heavy rain to portions of the western
Caribbean with potentially significant flooding across western Cuba
and the northeastern Yucatan Peninsula into early Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  25/2100Z 22.5N  86.6W   75 KT  85 MPH
 12H  26/0600Z 24.1N  86.2W   95 KT 110 MPH
 24H  26/1800Z 27.4N  85.2W  115 KT 130 MPH
 36H  27/0600Z 32.1N  84.6W   70 KT  80 MPH...INLAND
 48H  27/1800Z 36.1N  86.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 60H  28/0600Z 37.1N  88.1W   25 KT  30 MPH...POST-TROP/EXTRATROP
 72H  28/1800Z 36.8N  88.7W   20 KT  25 MPH...POST-TROP/EXTRATROP
 96H  29/1800Z 37.0N  88.0W   15 KT  15 MPH...POST-TROP/EXTRATROP
120H  30/1800Z...DISSIPATED

$$
Forecaster Berg

[Tallis Rockwell]

45 minutes ago, SnowGoose69 said:

This is the furthest east run yet by the NAM, comes in E of TLH

The NAM is also showing a sub 870 beast so I don't know how seriously I'd take it.

[jrips27]

No east shift to my eye

[SnowGoose69]

Just now, jrips27 said:

No east shift to my eye

If anything its like 10 miles further west 

[NorthHillsWx]

5pm was one of the more dire sounding advisories you’ll hear from NHC

[TPAwx]

35 minutes ago, Hotair said:

Very windy and drenching rain in Tampa now.  Soil is going to be saturated soon  

 

not good 

 

 

 

That was a hefty band.  The precip forecast is pretty modest, but yeah ground is soaked and all the retention ponds and canals are as high as they’ve been all year.

[Blizzard22]

3 minutes ago, SnowGoose69 said:

If anything its like 10 miles further west 

Do you know why they moved it further west ?

[batmanbrad]

1 minute ago, SnowGoose69 said:

If anything its like 10 miles further west 

I'd say even more than that; previous NHC advisory had LF around Apalachee Bay, now the cone center looks to be around Port St. Joe/Apalachicola area, I'd say 40-50 mile west shift?

[NorthHillsWx]

It’s probably been said on here but Atlanta to the upstate and Asheville need to prepare for extended outages and tree damage on top of historic flooding. This is going to be one those areas never forget, sadly. Seems pretty locked in at this point

[beanskip]

5 minutes ago, SnowGoose69 said:

If anything its like 10 miles further west 

I just don't get it. Even if they are leaning toward the hurricane models -- none of them pass west of Tallahassee. 

[Prospero]

 

The Storm Surge prediction this time yesterday was almost all Greater than 9 feet above ground in our area so great news for Gulfport FL if this is more accurate. We are pretty used to 3 to 6 feet surges.

https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/152934.shtml?inundation#contents

[Amped]

975mb dropsonde.

[Wannabehippie]

17 minutes ago, weatherCCB said:

85mph 978mb 

with the 5pm update

Full update.

4:00 PM CDT Wed Sep 25
Location: 22.5°N 86.6°W
Moving: N at 12 mph
Min pressure: 978 mb

[marsman]

5 minutes ago, Prospero said:

 

The Storm Surge prediction this time yesterday was almost all Greater than 9 feet above ground in our area so great news for Gulfport FL if this is more accurate. We are pretty used to 3 to 6 feet surges.

...

 

Even better for the Fort Myers area, nearly nonexistent. If I still lived there, I wouldn't be partying yet.

[jrips27]

Pretty jarring

511 PM EDT Wed Sep 25 2024

...TROPICAL STORM WARNING IN EFFECT...

A Tropical Storm Warning means tropical storm-force winds are
expected somewhere within this area within the next 36 hours

* LOCATIONS AFFECTED
    - Atlanta

* WIND
    - LATEST LOCAL FORECAST: Equivalent Strong Tropical Storm force
      wind
        - Peak Wind Forecast: 45-60 mph with gusts to 85 mph
        - Window for Tropical Storm force winds: early Friday morning
          until Friday afternoon

[OSUmetstud]

Theres no issue with the nhc forecasts. They are consistent with the hurricane models in terms of track and landfall position. 

[LithiaWx]

6 minutes ago, OSUmetstud said:

Theres no issue with the nhc forecasts. They are consistent with the hurricane models in terms of track and landfall position. 

nasty track for Metro ATL for winds if the core passes just west of the city.

[SchaumburgStormer]

1 minute ago, LithiaWx said:

nasty track for Metro ATL for winds if the core passes just west of the city.

Forward speed and size of this thing is going to really surprise some folks far inland. 

[Hotair]

From an impact perspective would a more Easterly track away from Tally cause less storm surge issues for folks there?  As the wind field would be predominantly pushing out to sea?  

[WxWatcher007]

5 minutes ago, OSUmetstud said:

Theres no issue with the nhc forecasts. They are consistent with the hurricane models in terms of track and landfall position. 

Despite the globals, the consensus hasn’t changed. Makes it hard to bet against. Having been through a lot of these now, it’s almost always coming down to the final hours for precise landfall location.

That’s just how it goes. Folks just have to be ready for anything. 

[beanskip]

6 minutes ago, OSUmetstud said:

Theres no issue with the nhc forecasts. They are consistent with the hurricane models in terms of track and landfall position. 

Would love clarification on this -- I'm looking at 12z GFS/12z Euro/12z UK/12z ICon all showing landfall in Taylor County which is now outside or just on the eastern border of the cone. Are they all being discounted? 

[SnowGoose69]

1 minute ago, LithiaWx said:

nasty track for Metro ATL for winds if the core passes just west of the city.

Since no model shows the track NHC has I took the euro and extrapolated the winds it has for airports west of Augusta and it would likely be 55-60kt gusts for ATL

[Jtm12180]

37 minutes ago, jrips27 said:

The NHC intensity forecast now shows an intensity of 115 kt (Category 4) at
24 hours, which is mirrored by several of the regional hurricane
models and the SHIPS guidance.  It should be noted that additional
strengthening is possible beyond 24 hours before Helene makes
landfall Thursday evening.

And there's no way 130mph will be the ceiling IMO...NHC is so hesitant to forecast intensity even when all the proof is there that conditions are going to be ideal

[NeonPeon]

3 minutes ago, Jtm12180 said:

And there's no way 130mph will be the ceiling...NHC is so hesitant to forecast intensity when all the proof is there that conditions are going to be ideal

I don't know what you mean. Their prediction is on the upper envelope of the intensity guidance they have, and they reference that it could be higher. That's hardly hesitancy, it seems very reasonable.

Lastly, it's the spectators that care whether it hits this or that imaginary threshold. In terms of the impact this thing is being painted as the monster it is. A lot of the numbers are trivia. 

[LithiaWx]

26 minutes ago, NorthHillsWx said:

It’s probably been said on here but Atlanta to the upstate and Asheville need to prepare for extended outages and tree damage on top of historic flooding. This is going to be one those areas never forget, sadly. Seems pretty locked in at this point

I'm in my 40's and still remember Opal.  Smaller storm at different angle but that was memorable in Atlanta.

[TJW014]

3 minutes ago, Jtm12180 said:

And there's no way 130mph will be the ceiling IMO...NHC is so hesitant to forecast intensity even when all the proof is there that conditions are going to be ideal

Their intensity/position forecast is in 12 hour intervals. There's time in between the 24 hour fix/strength and when it makes landfall. That's why they note that further strengthening is possible up until landfall after 24 hours

[Allsnow]

 

[TPAwx]

27 minutes ago, Prospero said:

 

The Storm Surge prediction this time yesterday was almost all Greater than 9 feet above ground in our area so great news for Gulfport FL if this is more accurate. We are pretty used to 3 to 6 feet surges.

https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/152934.shtml?inundation#contents

Guidance for TB remains at 5-8 feet.  

[SnowGoose69]

4 minutes ago, NeonPeon said:

I don't know what you mean. Their prediction is on the upper envelope of the intensity guidance they have, and they reference that it could be higher. That's hardly hesitancy, it seems very reasonable.

Lastly, it's the spectators that care whether it hits this or that imaginary threshold. In terms of the impact this thing is being painted as the monster it is. A lot of the numbers are trivia. 

I was surprised honestly they went that aggressive.  They rarely will go too nuts on intensity fcsts as its still hard to predict