Major Hurricane Helene

[Radtechwxman]

2 minutes ago, dan11295 said:

From La Bajada radar you can tell the environment around the core is moistening and appears to be in process of working out any remaining dry air from the circulation.

Still a good bit to work out on northern edge of COC. The better environment tonight should help really accelerate things. 

[WxWatcher007]

5 minutes ago, beanskip said:

HEY METS!

I've been on this board for as long as it has existed.

I have an NHC Cat 3 track line going right over my house.

I've always seen these boards as place to learn and share.

I have what I think is a valid question and would appreciate somebody educating me.

Thanks! 

 

3 minutes ago, buckeyefan1 said:

I’m far from being a met, but I’ll say that they’re thinking the ULL pulls it a touch further west as opposed to the usual poleward tug nne-ne? 

I think it’s also really important to note that even the NHC hasn’t quite honed in on that final landfall point yet. This is from their 11am discussion:

The track guidance remains tightly clustered,
and the NHC forecast is generally just an update of the previous
prediction. It is still too soon at this point to be overly focused
on an exact landfall location and time, since NHC track forecasts
can be off by an average of 60 nm at the 36-hour forecast time.

Anyone in the cone should be ready for a direct impact. Francine just a few weeks ago with the last minute east trend is a good example of why. Personally, I’m still hedging for a landfall slightly further east. 

[jrips27]

Hey everyone! Just finally logged back in after lurking the past several days. I'm in downtown Atlanta where heavy rain looks like it's really going to start to pile up over the next few hours. Commute home back to the northern suburbs looks pretty miserable. Have tried to get the word out today that people need to be prepared for something possibly extraordinary.

Hard to imagine the rain totals NWS FFC is spitting out. There's going to be considerable urban flash flooding downtown as there are parking lots that flood when we get a heavy summer thunderstorm. 

Agree with most everyone on here that a little shift east would allow Atlanta to avoid the worst case scenario tomorrow night with winds.

Stay safe everyone!

[CoastalWx]

Not much of a move on the 18z tropical models. Maybe a tad more spread to the E, but overall pretty consistent location wise. 

[GaWx]

8 minutes ago, CoastalWx said:

Not much of a move on the 18z tropical models. Maybe a tad more spread to the E, but overall pretty consistent location wise. 

Do you mean the 12Z runs? It’s too early for 18Z runs of HWRF, HMON, etc. Which models are you referring to? Are you talking about different models?

[csnavywx]

Some evidence on visible that there's still a bit of southeasterly shear undercutting the outflow layer. Will probably act as a bit of a braking mechanism until it starts getting some actual movement to the north and shear cuts to near zero.

[CoastalWx]

2 minutes ago, GaWx said:

Do you mean the 12Z runs? It’s too early for 18Z runs of HWRF, HMON, etc. Which models are you referring to? Are you talking about different models?

[GaWx]

5 minutes ago, CoastalWx said:

Thanks. I know it says 18Z guidance, but I don’t see how those can be actual 18Z runs since they haven’t run yet. I believe those are mainly 12Z run tracks. They include UKMET, GFS, HWF, etc.

 Anyone else have more insight on this?

[Hotair]

Model track guidance is adhering to the Fujiwara effect

 

 

 

[OSUmetstud]

18z early cycle models are 12z models corrected for the current position

[StantonParkHoya]

Interesting. Most go west of ATL it appears.

[CoastalWx]

1 minute ago, OSUmetstud said:

18z early cycle models are 12z models corrected for the current position

I also was under the impression that some are also new and these plots are positions extracted from the grib files etc. The HWRF shown on that is definitely different compared to the 12z runs. 

 

Admittedly though I'm not 100% sure how those early runs are collected.

[WEATHER53]

1 hour ago, gymengineer said:

Storm surge forecast update in the intermediate advisory that will probably result in an updated graphic at 5 pm: 

Carrabelle, FL to Chassahowitzka, FL...12-18 ft
Apalachicola, FL to Carrabelle, FL...8-12 ft
Chassahowitzka, FL to Anclote River, FL...8-12 ft
Indian Pass, FL to Apalachicola, FL...6-9 ft

When there is a 12-18’ surge, how far inland  will it go before its down to like 6”-1’ of surge remaining?

[OSUmetstud]

7 minutes ago, CoastalWx said:

I also was under the impression that some are also new and these plots are positions extracted from the grib files etc. The HWRF shown on that is definitely different compared to the 12z runs. 

 

Admittedly though I'm not 100% sure how those early runs are collected.

This is from u of Wisconsin

Consequently, "early" models represent forecasts from the previous cycle - that beginning 9 hr prior to an official forecast - that are shifted forward in time by 6 hr with a position and intensity matching the storm's current attributes. For dynamical models, these models have designators that end in an I (e.g., AVNI, CMCI, etc.) to indicate their interpolated nature. Note that consensus, statistical, and statistical-dynamical guidance is also classified as "early" guidance since each are derived using "early" model inputs. Conversely, "late" models represent forecasts from the current forecast cycle that arrive late, or after the official forecast must be made. They form the basis for the next forecast cycle's "early" model forecasts. They have no special designator notation.

[gymengineer]

Isn't part of the issue with this particular track graphic that only straight lines are used between time dots? So, with a fast moving hurricane, you wouldn't be able to discern changes in direction within a 12-hr window. With Helene, what happens between the 24-hr and 36-hr dot on this 18Z graphic is landfall, which would not be accurately captured if the model is depicting any change in direction during that window. 

[franklin NCwx]

1 hour ago, NeonPeon said:

Many models show some horrific rotting band somewhere near transylvania county. NHC starting to show some 20" plus stuff there. Obviously the details of where it sets up are up in the air, but those are astonishing totals for an area that broadly is at massive flood risk in general (i.e.20%+ of properties at risk)

Large elevation gain at the Transylvania Jackson County line. That area enhances due to orographic lift

[WxWatcher007]

Starting to get the first far flung outer rain bands here and across much of Florida. Speaks to how expansive this thing is already. 

[olafminesaw]

i don't  know anything about this model output, but I believe it is what the NWS bases their forecast on

https://slosh.nws.noaa.gov/psurge/index.php?R=CONUS&S=Helene2024&Adv=9&Ty=e10&D=agl&Ti=cum&Msg=17&Mp=Street&Z=5&Lt=34.823193&Lg=-79.693886&Help=about

[Allsnow]

The pre from Helene already effecting the ATL area 

[DeltaPilot]

It sure is Allsnow. Been pouring off and on here since about 1130 am. Looks to go on for the rest of tonight and into tommorow, then we get the northern bands from Helene.

[soadforecasterx]

looks like its really getting its act together now

[SchaumburgStormer]

2 minutes ago, soadforecasterx said:

looks like its really getting its act together now

Yep, should be off to the races this evening. Minimal land interaction really has this one looking much better already than I thought it would a few days ago. 

[LithiaWx]

Is RI still forecast overnight?

[SnowGoose69]

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

[Prospero]

22 minutes ago, WxWatcher007 said:

Starting to get the first far flung outer rain bands here and across much of Florida. Speaks to how expansive this thing is already. 

Had our first taste of Helene with TS gusts all around in the area in a small band. I was outside and this storm just feels really "big".

Egmont Channel at the mouth of Tampa Bay had a gust of 47 mph and 38 mph winds for a moment. We are still a long ways from the center.

[schoeppeya]

21 minutes ago, soadforecasterx said:

looks like its really getting its act together now

Pretty close to getting the dry air mixed out of the center. Recon is almost there, should be an interesting couple hours. 

[NorthHillsWx]

Me thinks this is going to be storm porn as it relates to a classic looking eye when it peaks. Getting the look already 

[Hotair]

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

 

not good 

 

 

 

[Amped]

One hottower stuck in the middle of the eye.   It has little if any meteorological impact, but is great at blocking our view of the eye while it forms. 

 

[Radtechwxman]

That dry air definitely made it into the COC. Degraded it more than I anticipated. Curious what hurricane hunters will find intensity wise. Wondering when Helene will really take off.