ATL: HELENE - Post-Tropical - Discussion

[Powellrm]

Tropical storm warnings now appear to extend west through Okaloosa County.

[url]https://iili.io/dLVlJAF.md.png [/url]

ICON continues to be east of this track. Super curious to see the next update.

[hiflyer]

I guess we all remember Katrina 20 years ago…came off Florida weak and hit the loop current and went into New Orleans as a cat 5. Bringing it up as current forecast path has Helene staying close to it for a ways after riding past Yucatan/Cuba in it. That is a lot of deep warmer water to be near.

[Pipelines182]

Judging from the satellite appearance, Helene is dealing with some wind shear, the CDO has become asymmetric. There's also signs of dry air entrainment, the CDO is warming and there's signs of thunderstorms collapsing with the outflow boundaries streaming off the southern and western sides. No RI for the time being.

I don't see that. Outflow is unrestricted and whatever pulsing of convection and cloud tops appear to me as nothing greater than part of the diurnal processes still at hand until the systems core is fully developed (getting close). I will say this though, there is a small upper level of dry air capping between 200mb and 300mb that might be slightly affecting the system's vertical vorticity where RH is showing to be only 40-50% within that layer (as depicted on the 6Z GFS vertical cross-section graphs - https://www.tropicaltidbits.com/analysi ... 92506&fh=1 ) from about Longitude 85.5 and points westward. I'm sure that NHC clearly sees that, and why RI is practically a given after the hurricane begins moving northward and especially as it begins motion east of due north.

If you look back to 12z you can see a large outflow boundary coming out of the CDO on the SW half, that's a sign of a large collapse of thunderstorms. The feathery cirrus outflow that's continuing is another sign of continued dry air entrainment. The diurnal process isn't that significant for hurricanes, and they don't cause drastic warming/cooling of the CDO in short time frames.

[Jr0d]

I cant say I agree with the NHC saying Helene is moving NNW given these center low pressure fixes show slightly east of north movement.

https://i.ibb.co/tLGMgKG/recon-AF309-1109-A-HELENE-6.png

You are right but as you probably also know their motion goes by several hours prior to the write up.

We should get another Air Force center fix shortly. It should confirm the NNE turn has begun.

Also the NOAA fixes showed the same motion.

[tronbunny]

NWS Tallahassee just updated their forecast:

THURSDAY NIGHT
SHOWERS WITH A CHANCE OF THUNDERSTORMS. SOME
THUNDERSTORMS MAY PRODUCE HEAVY RAINFALL. HURRICANE FORCE WINDS
WITH LOWS IN THE LOWER 70S. EAST WINDS 70 TO 90 MPH WITH GUSTS UP
TO 120 MPH, BECOMING SOUTHWEST AND DIMINISHING TO 25 TO 30 MPH
WITH GUSTS UP TO 40 MPH AFTER MIDNIGHT. CHANCE OF RAIN NEAR
100 PERCENT.

I'd get the heck out of there - even if you're OK in the spot you are, you'll be living without power for an extended period of time if this forecast verifies.

[/quote]
That was my advice to family who live north center of Tally with very tall trees on the property. Almost every tree is a hazard to the home.

[xironman]

That will be one big eye, "akin to a tire or doughnut" LOL

[tolakram]

Key West saved loop

[ROCK]

Little concerned about inland winds up into Atlanta. Got multiple asset around the city that probably hasn't seen high end TS force winds before unless in typical Tstorms. NHC has this a TS up almost to TN.

[Kingarabian]

Center is getting closer to the leading edge of the CDO so it probably means a temporary CCC is in place. Likely meaning that intensification could slow down for a few hours until the dry air is mixed out.

[tolakram]

Center is getting closer to the leading edge of the CDO so it probably means a temporary CCC is in place. Likely meaning that intensification could slow down for a few hours until the dry air is mixed out.

CDO = central dense overcast
CCC = ?

[xironman]

The slight dry air issues were taken into account on the 06z HWRF. Note the band of lower (50%) RH on the east side of the core.

https://i.ibb.co/FHhwHgg/hwrf-mid-RH-09-L-3.png

Now compare this to visible imagery right now and it's clear to see.

https://i.ibb.co/f1SmrTb/Helene-2.jpg

Despite this, the HWRF still peaks it right around landfall as a mid-range cat 3.

The funny thing is, looking at the radar that area will become part of the huge eye.

[tolakram]

saved loop


source: https://weather.cod.edu/satrad/?parms=m ... =undefined

[xironman]

Center is getting closer to the leading edge of the CDO so it probably means a temporary CCC is in place. Likely meaning that intensification could slow down for a few hours until the dry air is mixed out.

CDO = central dense overcast
CCC = ?

Google - "Ironically, one of the largest and coldest eruptions of convection near the core of a TC, the central cold cover (CCC), indicates slowed or arrested development "

[Zonacane]

Center is getting closer to the leading edge of the CDO so it probably means a temporary CCC is in place. Likely meaning that intensification could slow down for a few hours until the dry air is mixed out.

This is very wrong, there's a tongue of dry air getting wrapped in, but the intensity models show this getting mixed out very quickly. There is no shear or CCC developing. The dry slot makes the outline of the formative eye very obvious

[tolakram]

Center is getting closer to the leading edge of the CDO so it probably means a temporary CCC is in place. Likely meaning that intensification could slow down for a few hours until the dry air is mixed out.

CDO = central dense overcast
CCC = ?

Google - "Ironically, one of the largest and coldest eruptions of convection near the core of a TC, the central cold cover (CCC), indicates slowed or arrested development "

Google Hurricane CCC

Civilian Conservation Corps Camp in Hurricane, Utah

It's nice when our users here don't have to google all the answers.

[KC7NEC]

Update: We’ve been evacuated from the resort in St. Pete Beach due to mandatory evacuations for Zone A in Pinellas County. We’re now in Tampa and waiting to see how things unfold.

[tolakram]

We do have a local thread now. It's optional, unlike the model thread where we like to stay on topic. Sometimes discussion of local events makes more sense in a local thread and can get more discussion from folks in the same area or experiencing the same thing.

https://www.storm2k.org/phpbb2/viewtopi ... 9&t=124348

[Kingarabian]

Center is getting closer to the leading edge of the CDO so it probably means a temporary CCC is in place. Likely meaning that intensification could slow down for a few hours until the dry air is mixed out.

This is very wrong, there's a tongue of dry air getting wrapped in, but the intensity models show this getting mixed out very quickly. There is no shear or CCC developing. The dry slot makes the outline of the formative eye very obvious

It's a now casting Dvorak observation and is temporary.

[acidus]

Can you believe this guy? People listening to him could be putting their lives in danger!

Huge News! Helene Will Not Be A Major Hurricane On Landfall!
https://www.youtube.com/watch?v=GG3nS9ZAxZ4&lc

The posts in this forum are NOT official forecasts and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the NHC and NWS.

[chaser1]

I'm not gonna lie this "Best spot for the storm to go discussion" is useless imo. I'll tell you, when I was chasing Idalia in Perry last year and staring at people's homes with trees through the middle and businesses without roofs, I definitely wasn't thinking "Well this was the best place for this storm to go!" I'm not a fan of this discussion it feels insensitive to the people who live there. There's nothing to be gained from it, we can't control where these go.

Communication in general is entirely based upon "context". Imagine being in some bar and overhearing conversation where people are chatting with statements such as "oh, I hope Perry gets slammed by the storm", or "who cares if Perry gets erased from existence since it's such a small town". That would be horrible and completely insensitive. When you consider this forum as a space where students, professionals and enthusiasts of severe weather congregate to discuss the science and academics of hurricanes, one need consider "the context" that certain statements are made. I've chased hurricanes from Puerto Rico, to North Carolina, Luisiana and Florida. The range of adrenaline and emotion range from exhilaration from witnessing the fury of Mother Nature to the despair of destruction once over, especially knowing that I'm just here for the view but not left to deal with the death, pain and destruction and the time to rebuild. Do you still have the desire to chase hurricanes or severe weather? If so, that doesn't make you any less sensitive to the suffering then it does for a kid to want to grow up and become a meteorologist.

When one considers that many on this (or other) forums live throughout the U.S., Caribbean, and some from countries around the world, most know where the larger population and tourist locations are. "Thank heaven the storm is hitting there (pick the sparse or rural area of choice) instead of ______" (pick whichever large city or vacation destination that your knowledge base can relate too), is generally meant in the context of least amount of harm/damage. Sadly, it can come across as "better that the storm hits you than me" but I don't believe most here intend to imply that.