ATL: HELENE - Models

[TomballEd]

Interesting the swaying on intensity between the 12Z models, the18Z high res hurricane models, and the 0Z models.

I wouldn't write this off after one model cycle.

[ElectricStorm]

HAFS-B strong Cat 4

[Bocadude85]

HAFS-B strong Cat 4
https://i.imgur.com/GxcaqWdpng

Also east of the 18z, one more nudge east and Tampa has a big problem.

[ElectricStorm]

HAFS-A and HMON both have mid-range Cat 4s before weakening slightly before landfall, HMON around 110kts and HAFS-A around 115kts

[Keldeo1997]

Looks like the 18Z runs were an outlier. Hurricane models are back with the CAT4-5 solutions. I don't think I've ever seen this much agreement on expecting explosive Deeping in the gulf before

[Teban54]

Others like Kevin may post more detailed analyses later, but here's a quick rundown of 0z hurricane models:

• HAFS-A: Peak 936 mb / 124 kt, landfall 936 mb / 117 kt
• HAFS-B: Peak 923 mb / 134 kt, landfall 923 mb / 128 kt
• HMON: Peak 925 mb / 127 kt, landfall 925-929 mb / 122 kt
• HWRF: Peak 921 mb / 121 kt, landfall 922-924 mb / 119 kt

(Pressure and wind peaks may not be at the same time)

[ConvergenceZone]

Early 0z intensity guidance is noticeably weaker with only one reaching Cat 3, compared to 18z which had Cat 4s and a couple 5s. We'll see if hurricane models do the same although a lot of times their solutions are stronger than these.
https://i.imgur.com/d23Kuc6.png

That's actually quite surprising. But the only way I see NHC lowering the landfall intensity is if the models continue to show it weaker tomorrow, then I think they will drop landfall to a Cat 2

[ConvergenceZone]

Looks like the 18Z runs were an outlier. Hurricane models are back with the CAT4-5 solutions. I don't think I've ever seen this much agreement on expecting explosive Deeping in the gulf before

But aren't the GFS and EURO about the same or slighting weaker? From what I understand those are the more reliable models.

[Bocadude85]

Looks like the 18Z runs were an outlier. Hurricane models are back with the CAT4-5 solutions. I don't think I've ever seen this much agreement on expecting explosive Deeping in the gulf before

But aren't the GFS and EURO about the same or slighting weaker? From what I understand those are the more reliable models.

GFS and Euro are not intensity models, look at them for track not strength.

[Poonwalker]

HWRF shows a 922 into big bend. Pretty tight consensus on the landfall being big bend area. Slight east shift maybe overall. Much stronger storm this run with cat 4 other than Gfs and Euro.

[Woofde]

Looks like the 18Z runs were an outlier. Hurricane models are back with the CAT4-5 solutions. I don't think I've ever seen this much agreement on expecting explosive Deeping in the gulf before

But aren't the GFS and EURO about the same or slighting weaker? From what I understand those are the more reliable models.

The GFS and Euro are track kings, intensity is a different ball game. The GFS has glimpses of skill, though when you start to get sub ~960mb it's resolution means it can't hold up.

The Euro really should not be used for intensity in strong storms. For example during Beryl even while it was actively a Category 5, the Euro repeatedly only showed pressures in the 970s.

[ElectricStorm]

Looks like the 18Z runs were an outlier. Hurricane models are back with the CAT4-5 solutions. I don't think I've ever seen this much agreement on expecting explosive Deeping in the gulf before

But aren't the GFS and EURO about the same or slighting weaker? From what I understand those are the more reliable models.

Euro is most definitely not reliable for intensity, especially in storms that are expected to be on the stronger side like this one. GFS is okay to an extent but once a TC actually forms the hurricane models are generally going to be much more accurate.

0z hurricane models all have at least a mid-range Cat 4 which considering the favorable environment seems like a pretty plausible solution, certainly much more so than the HAFS at 12z (way too strong) and 18z (too weak)

[Poonwalker]

Hafs was specifically tailored to help nail down intensity forecasts. It was something around 30 percent improvement in that department before being released to the public.

[shah83]

People are not paying enough attention to the rainfall risks with this storm. Icon in particular is showing disastrous rains for eastern Tennessee, and others are showing very heavy rains in Tenn and N.C. mountains.

[ConvergenceZone]

Looks like the 18Z runs were an outlier. Hurricane models are back with the CAT4-5 solutions. I don't think I've ever seen this much agreement on expecting explosive Deeping in the gulf before

But aren't the GFS and EURO about the same or slighting weaker? From what I understand those are the more reliable models.

GFS and Euro are not intensity models, look at them for track not strength.

if that's the case, then why do so many comment on the pressure it's showing at landfall?

[ConvergenceZone]

People are not paying enough attention to the rainfall risks with this storm. Icon in particular is showing disastrous rains for eastern Tennessee, and others are showing very heavy rains in Tenn and N.C. mountains.

That's because the storm is going to be moving incredibly fast.

[kevin]

I'll start with the full overview again for 06z, but here are the blends only for 00z and 18z. 18z, as already discussed, was much weaker due to the HAFS runs. The blend only supports a high-end cat 2 landfall. 00z is more in-line with the runs before that. It blends to a peak around 928 mb with a mid-range cat 4 intensity of 121 kt. No longer the high-end cat 4/low-end cat 5 blend of the 12z runs, but if the recent models show anything it's how uncertain the situation still is. One note is that the 00z models are slightly slower than yesterday's 12z runs and have landfall delayed by about 6 hours. With RI-systems these small differences could have big impacts.

00z Blend
PEAK: 928 mb @ 72 hrs | 121 kt @ 66 hrs
hr / pressure (mb) / wind (kt)
00 / 1000 / 31 - TD
06 / 1000 / 39 - TS
12 / 998 / 45
18 / 993 / 51
24 / 987 / 54
30 / 982 / 56
36 / 975 / 71 - C1
42 / 968 / 68
48 / 960 / 82
54 / 947 / 100 - C3
60 / 936 / 111
66 / 930 / 121 - C4
72 / 928 / 109 - landfall
78 / 956 / 55

18z Blend
PEAK: 951 mb @ 78 hrs | 94 kt @ 72 hrs
hr / pressure (mb) / wind (kt)
00 / 1004 / 33 - TD
06 / 1002 / 38 - TS
12 / 999 / 39
18 / 997 / 41
24 / 993 / 49
30 / 991 / 47
36 / 984 / 53
42 / 982 / 59
48 / 980 / 58
54 / 976 / 60
60 / 970 / 73 - C1
66 / 961 / 86 - C2
72 / 955 / 94
78 / 951 / 83 - landfall
84 / 964 / 51

[kevin]

06z ICON, strongest ICON run to date with a landfall intensity of 961 mbar, +66 hrs. Landfall just north of Cedar Key.

[chris_fit]

00z GEFS... Quite a bit right.

[kevin]

Shear (SFC-1 km and SFC-3 km) on the center of PTC9 over the next 24 hours according to 06z GFS.

Hours from 06z - Shear SFC-1 km - Shear SFC-3 km

00 / 8 kt / 10 kt
03 / 6 kt / 12 kt now
06 / 9 kt / 15 kt
09 / 7 kt / 2 kt
12 / 1 kt / 6 kt
15 / 2 kt / 8 kt
18 / 1 kt / 7 kt
21 / 3 kt / 6 kt
24 / 2 kt / 5 kt