ATL: HELENE - Models

[StPeteMike]

Steve, the trough currently about to move off of Texas looks relatively still strong and intact, maybe weaker further north near Mississippi/Alabama border.

You don’t expect that to be the factor in if this goes more east than NHC has forecasted?

[Steve]

Steve, the trough currently about to move off of Texas looks relatively still strong and intact, maybe weaker further north near Mississippi/Alabama border.

You don’t expect that to be the factor in if this goes more east than NHC has forecasted?

Yeah I do. It's going to catch some of the moisture if not the entire circulation. But that looks to happen when it's north of Georgia. For now it will just tug at it. If it goes more east it's still going to have to come up north(ish) at some point because the cut off will get it. FWIW the cut off looks to stick around for a few days before the next pattern comes down. For instance, ICON is a bit east of the other guidance (early cycles, mesoscales and NHC). Watch how it handles the trough and Helene at 500mb.

https://www.tropicaltidbits.com/analysi ... 92412&fh=6

You can run it vort/wind as well at 500mb

https://www.tropicaltidbits.com/analysi ... 412&fh=144

[lsuhurricane]

This GFS run did not initialize correctly, location yes, strength no.

[CronkPSU]

GFS looks slower thru 48 but same basic spot

[MetroMike]

This GFS run did not initialize correctly, location yes, strength no.

Was it below or above in strength?

[Jr0d]

I have noticed the mesoscale models, (NAM, FV3, WRF, ect).almost all are showing the cutoff low a bit further east this morning, resulting in a slight east shift with Helene. While I know they are not good for tropical systems, they are good at sniffing out upper air features before the global models.

Again the timing is going to be crucial, when Helene makes the northeast turn tomorrow is a key timing point. If the storms grows in size(not necessarily in strength) faster than expected it will likely feel the trough and begin that turn sooner. If it is more compact than expected, my guess is it will take the turn later....then Thursday again the timing of a more north turn is going to be crucial.

It seems to me this cutoff low from the trough is adding extra complexity to the future track, despite the models being in great agreement. If I recall correctly they were in agreement for Ian too.

[CronkPSU]

This GFS run did not initialize correctly, location yes, strength no.

Was it below or above in strength?

slightly below

[CronkPSU]

not much change with the newest GFS, same basic spot for landfall, slightly weaker

[chris_fit]

12z GFS Trend

[Steve]

I have noticed the mesoscale models, (NAM, FV3, WRF, ect).almost all are showing the cutoff low a bit further east this morning, resulting in a slight east shift with Helene. While I know they are not good for tropical systems, they are good at sniffing out upper air features before the global models.

Again the timing is going to be crucial, when Helene makes the northeast turn tomorrow is a key timing point. If the storms grows in size(not necessarily in strength) faster than expected it will likely feel the trough and begin that turn sooner. If it is more compact than expected, my guess is it will take the turn later....then Thursday again the timing of a more north turn is going to be crucial.

It seems to me this cutoff low from the trough is adding extra complexity to the future track, despite the models being in great agreement. If I recall correctly they were in agreement for Ian too.

Yeah because there are always some random variables that we didn't see coming exactly the way they work out. Things will change from day to day though the overall pattern will be similar. Remember last Friday when the cut off was in the plains relative to landfall and there was a much more likely Biloxi/Mobile/Pensacola. A little farther east and it was Santa Rosa Beach/Destin then 30A and PCB and then the Bay (Apalachicola - just north of Tampa). It continued to progress farther east over time in the model runs so will it be farther east again still in a couple of model cycles or in reality? We gotta stay tuned for that.

[Hypercane_Kyle]

12z GFS initialization looked very poor, too weakand too far west.

[Gums]

Salute!

We Panhandle vets hoping the latest models are close to what shall actually transpire. Sorry for folks over where the last storm went thru, but most of the weak trees went down and with new grid cables and towers, electricity problems might not as bad as before.

I have not seen a good SLOSH model or others dealing with surge, anybody? If the eye stays east of St Marks, then many less folks need to fret. And they will also see much less wind.

For those interested, we "survived" Michael from just 60 miles west of landfall by Tyndall...got zilch rain and 30 mph gusts, but a fresh breeze from north of maybe 15-20 mph. The model 24 hours out showed the turn to east and we waited until it happened, but were packed and ready to zoom west.

Gums sends...

[WxEp]

Even though GFS ended up in roughly the same spot at landfall, I noticed two main differences in how it got there. First, Helene made it further west early on and actually appears to cross over or near the tip of the Yucatán Peninsula. At the same time, the cut-off low progressed further east. This lead to a further west "start point" in the GOM and Helene is well west of where it was on GFS 06z in the south GOM. As Helene traverses the GOM, however, the further east cut-off draws it toward FL at a sharper angle which leads to the landfall point being almost unchanged.

[aspen]

Don’t know what’s up with the GFS trying to form another low north of Helene’s center on approach to Florida. Perhaps it’s trying to string out the vorticity as a consequence of initializing weaker.

[HurricaneBelle]

Honestly, everyone along the west coast north of Port Charlotte should be on watch. Just for reference, a day before Idalia made landfall, the 06z on many of the models had landfall near Carrabelle on the other side of the Big Bend. That was just over 24 hours before she made landfall south of Perry.

So things can change in a day and we have two days for that to happen here.

Also just for reference, here is the NHC projected track 72 hours prior to Idalia making landfall (it barely deviated in the interim), which they nailed:



This is why one relies on the NHC's track, not individual model runs.

[Powellrm]

12z GFS Trend

https://i.imgur.com/eicwfhs.gif

Keeping an eye on that H off the NC coast as this storm pushes North...

[StPeteMike]

Honestly, everyone along the west coast north of Port Charlotte should be on watch. Just for reference, a day before Idalia made landfall, the 06z on many of the models had landfall near Carrabelle on the other side of the Big Bend. That was just over 24 hours before she made landfall south of Perry.

So things can change in a day and we have two days for that to happen here.

Also just for reference, here is the NHC projected track 72 hours prior to Idalia making landfall (it barely deviated in the interim), which they nailed:

https://i.imgur.com/LlOi8rf.png

This is why one relies on the NHC's track, not individual model runs.

Thank you! I was trying to find a graphic of it to compare and just gave up.

[HurricaneBelle]

Thank you! I was trying to find a graphic of it to compare and just gave up.

Every graphic and advisory product the NHC issues is archived on their site:

https://www.nhc.noaa.gov/archive/2024/

This points to this year's archive but all the previous years are linked at the top of the page (or you can just substitute the year you want in the above URL)

[Nimbus]

I have noticed the mesoscale models, (NAM, FV3, WRF, ect).almost all are showing the cutoff low a bit further east this morning, resulting in a slight east shift with Helene. While I know they are not good for tropical systems, they are good at sniffing out upper air features before the global models.

Again the timing is going to be crucial, when Helene makes the northeast turn tomorrow is a key timing point. If the storms grows in size(not necessarily in strength) faster than expected it will likely feel the trough and begin that turn sooner. If it is more compact than expected, my guess is it will take the turn later....then Thursday again the timing of a more north turn is going to be crucial.

It seems to me this cutoff low from the trough is adding extra complexity to the future track, despite the models being in great agreement. If I recall correctly they were in agreement for Ian too.

NHC doesn't have much luck with cutoff lows EG Andrew,Charley, but this first split is early in the forecast so we have some time to see how the low position is going to evolve. the start of rapid intensification will also be important not only for places like Key West but surge prone bays all along the western coast of Florida have been built up at the 5-8 ft elevation so they walk a very fine line with major hurricanes on the current forecast track.

So the NNE turning point and how well Helene will be ventilated are going to be the things to watch first.

If Helene had headed for the middle of the gulf the trough dropping in over LA might have dug far enough south to shear Helene to pieces before landfall but there will be a high pressure over Helene for a couple days now after the cutoff low weakens and retreats.

[cycloneye]

 https://x.com/AndyHazelton/status/1838616803301560816