ATL: HELENE - Models

[kevin]

06z GFS, about 3 hours slower than previous runs in terms of landfall. Peaks at 960 mbar before a 961 mbar landfall just south of Steinhachee. Similar landfall location as 00z GFS.

[chris_fit]

06z GEFS. Man it just seems like it's getting closer to the peninsula last few runs.

[USTropics]

06z GEFS. Man it just seems like it's getting closer to the peninsula last few runs.

https://i.imgur.com/ozW5xyD.png

I think the GFS (and its ensembles) are having difficulty with the timing. I noticed the 06z GFS operational run is starting to slow things down (compared to the 00z and 18z guidance). The NHC mentioned this in the 5AM disco too:

The biggest change to the model guidance overnight is that the guidance mean is a bit slower, with the GFS model faster than most of the aids.

There still remains an unusually large north→south spread in the GFS ensembles for a such a short (48 hour) lead time:


Compared to the 00z ECWMF ensembles at the same valid time:

[Nimbus]

06Z GFS forecast for a little weaker ridging over Virginia this run which would become a serious problem if it turns out to be a trend.

[aspen]

06z HAFS-A/B seem to initialize decently. They show that as the system becomes better aligned, the LLC (which starts out right around where recon just found it) pivots to the west, getting to ~86W by the time it reaches the channel. Then it starts going bananas; HAFS-B has a Cat 5 on Thursday morning.

[SconnieCane]

06Z HAFS-A appears to be on a dangerous track for Tampa/Clearwater...

[kevin]

Both HAFS models are back to a cat 5 and imo they've initialized the system best together with HWRF. HMON initialized way too far SW imo and because of that almost makes landfall on Yucatan, disrupting intensification. Even though even the weaker HMON also makes this an intensifying cat 3 nearing landfall, so there are no good scenarios.

[Hypercane_Kyle]

HAFS-A/B, HWRF have both returned to the nuclear outputs we saw during yesterday's 12z suite.

[N2FSU]

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[N2FSU]

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[DunedinDave]

The angle at which it approaches the Big Bend/west coast is going to be so important. How hard of a right turn is it? And does it get that push to the right in that area that so many do. Hopefully it ends up land falling in one of the isolated areas along the big bend.

[kevin]

06z hurricane models blend. The weakest model in this cycle is HMON, which imo initializes too far SW resulting in land interaction with Yucatan. The other models cross the channel without land interaction and all blow up this system big time. To ensure that landfall occurs at the same time for all models used in the blend I used the +63 hr data point from HWRF for the +66 hr blend since HWRF makes landfall a few hours faster than the other models. Blended landfall intensity is 923 mbar. The most extreme blend was still yesterday's 12z with 913 mbar, but the 06z blend is stronger than 00z (928 mbar) and 18z (951 mbar).

HWRF
PEAK: 922 mb @ 63 hrs | 126 kt @ 63 hrs
hr / pressure (mb) / wind (kt)
00 / 1001 / 39 - TS
06 / 999 / 44
12 / 994 / 45
18 / 987 / 52
24 / 975 / 57
30 / 966 / 61
36 / 953 / 76 - C1
42 / 948 / 77
48 / 939 / 111 - C3
54 / 928 / 117 - C4
60 / 925 / 113 - landfall
66 / 928 / 77

HMON
PEAK: 941 mb @ 66 hrs | 109 kt @ 66 hrs
hr / pressure (mb) / wind (kt)
00 / 1000 / 33 - TD
06 / 1002 / 39 - TS
12 / 993 / 43
18 / 991 / 46
24 / 985 / 49
30 / 980 / 56
36 / 977 / 63
42 / 970 / 63
48 / 962 / 82 - C1
54 / 953 / 95 - C2
60 / 947 / 104 - C3
66 / 941 / 109 - landfall
72 / 959 / 55

HAFS-A
PEAK: 921 mb @ 66 hrs | 141 kt @ 57 hrs
hr / pressure (mb) / wind (kt)
00 / 994 / 32 - TD
06 / 997 / 46 - TS
12 / 995 / 52
18 / 988 / 54
24 / 985 / 52
30 / 978 / 68 - C1
36 / 969 / 80
42 / 962 / 86 - C2
48 / 946 / 109 - C3
54 / 932 / 128 - C4
60 / 926 / 139 - C5
66 / 921 / 134 - landfall
72 / 957 / 63

HAFS-B
PEAK: 909 mb @ 66 hrs | 152 kt @ 57 hrs
hr / pressure (mb) / wind (kt)
00 / 996 / 31 - TD
06 / 996 / 46 - TS
12 / 995 / 49
18 / 981 / 56
24 / 981 / 52
30 / 970 / 69 - C1
36 / 957 / 78
42 / 951 / 89 - C2
48 / 939 / 125 - C4
54 / 922 / 142 - C5
60 / 916 / 147
66 / 909 / 144 - landfall
72 / 972 / 60

Blend
PEAK: 913 mb @ 72 hrs | 132 kt @ 72 hrs
hr / pressure (mb) / wind (kt)
00 / 998 / 34 - TD
06 / 999 / 44 - TS
12 / 994 / 47
18 / 987 / 52
24 / 982 / 53
30 / 974 / 64
36 / 964 / 74 - C1
42 / 958 / 79
48 / 947 / 107 - C3
54 / 934 / 121 - C4
60 / 929 / 126
66 / 923 / 128 - landfall

[StPeteMike]

Clearly things can change and there’s been times they overdue intensity, but still find it crazy that many bomb her out to Cat 4 or stronger.

[cycloneye]

06z hurricane models blend. The weakest model in this cycle is HMON, which imo initializes too far SW resulting in land interaction with Yucatan. The other models cross the channel without land interaction and all blow up this system big time. To ensure that landfall occurs at the same time for all models used in the blend I used the +63 hr data point from HWRF for the +66 hr blend since HWRF makes landfall a few hours faster than the other models. Blended landfall intensity is 923 mbar. The most extreme blend was still yesterday's 12z with 913 mbar, but the 06z blend is stronger than 00z (928 mbar) and 18z (951 mbar).

HWRF
PEAK: 922 mb @ 63 hrs | 126 kt @ 63 hrs
hr / pressure (mb) / wind (kt)
00 / 1001 / 39 - TS
06 / 999 / 44
12 / 994 / 45
18 / 987 / 52
24 / 975 / 57
30 / 966 / 61
36 / 953 / 76 - C1
42 / 948 / 77
48 / 939 / 111 - C3
54 / 928 / 117 - C4
60 / 925 / 113 - landfall
66 / 928 / 77

HMON
PEAK: 941 mb @ 66 hrs | 109 kt @ 66 hrs
hr / pressure (mb) / wind (kt)
00 / 1000 / 33 - TD
06 / 1002 / 39 - TS
12 / 993 / 43
18 / 991 / 46
24 / 985 / 49
30 / 980 / 56
36 / 977 / 63
42 / 970 / 63
48 / 962 / 82 - C1
54 / 953 / 95 - C2
60 / 947 / 104 - C3
66 / 941 / 109 - landfall
72 / 959 / 55

HAFS-A
PEAK: 921 mb @ 66 hrs | 141 kt @ 57 hrs
hr / pressure (mb) / wind (kt)
00 / 994 / 32 - TD
06 / 997 / 46 - TS
12 / 995 / 52
18 / 988 / 54
24 / 985 / 52
30 / 978 / 68 - C1
36 / 969 / 80
42 / 962 / 86 - C2
48 / 946 / 109 - C3
54 / 932 / 128 - C4
60 / 926 / 139 - C5
66 / 921 / 134 - landfall
72 / 957 / 63

HAFS-B
PEAK: 909 mb @ 66 hrs | 152 kt @ 57 hrs
hr / pressure (mb) / wind (kt)
00 / 996 / 31 - TD
06 / 996 / 46 - TS
12 / 995 / 49
18 / 981 / 56
24 / 981 / 52
30 / 970 / 69 - C1
36 / 957 / 78
42 / 951 / 89 - C2
48 / 939 / 125 - C4
54 / 922 / 142 - C5
60 / 916 / 147
66 / 909 / 144 - landfall
72 / 972 / 60

Blend
PEAK: 913 mb @ 72 hrs | 132 kt @ 72 hrs
hr / pressure (mb) / wind (kt)
00 / 998 / 34 - TD
06 / 999 / 44 - TS
12 / 994 / 47
18 / 987 / 52
24 / 982 / 53
30 / 974 / 64
36 / 964 / 74 - C1
42 / 958 / 79
48 / 947 / 107 - C3
54 / 934 / 121 - C4
60 / 929 / 126
66 / 923 / 128 - landfall

Very good that you are doing the summary of all the models. Keep it on.

[ronjon]

One thing I'm noticing on most of the models is the extremely large wind field to the east of the center. On latest Euro runs, forecast winds of 64-80 kts at 850 mb level encompass the entire FL peninsula from central Florida north. Obviously not all of this will be translated to the surface but the hurricane models are showing similar findings. Seems this storm is forecast to be rather large with a huge windfield to the east of the center. This could have major implications on Florida's power network along with perhaps greater storm surge along the west coast.

[StPeteMike]

One thing I'm noticing on most of the models is the extremely large wind field to the east of the center. On latest Euro runs, forecast winds of 64-80 kts at 850 mb level encompass the entire FL peninsula from central Florida north. Obviously not all of this will be translated to the surface but the hurricane models are showing similar findings. Seems this storm is forecast to be rather large with a huge windfield to the east of the center. This could have major implications on Florida's power network along with perhaps greater storm surge along the west coast.

If she’s going to be a big girl, it makes sense that she is taking her time to get organized. John in the EPAC was small and that really helped him come together pretty quickly and what is expected with small core storms. Hopefully her large size helps lessen the rapid intensifying.

FWIW, did another meander of the Hurricane Michael models thread. At this time (2 days out) for Michael, HMON/HWRF were still west of landfall. HMON actually had it at Miramar Beach, which is roughly 85 miles west of Mexico Beach. Take the information for what it’s worth. Hopefully the years between, the models have improved greatly on pinpointing landfall/trajectory.

[GTStorm]

Question...are the models that run 3 hrs before an NHC advisory considered in that advisory...i.e., are the 6z models considered in the 5am NHC advisory?

[Steve]

Question...are the models that run 3 hrs before an NHC advisory considered in that advisory...i.e., are the 6z models considered in the 5am NHC advisory?

I'm sure they use the latest available data they have. They have access to tools and can use early and late cycle runs as well as their own to factor in. I guarantee you they have the stuff faster than it loads on tidbits or pivotal. I'm not sure how much faster because I've never been behind the curtain there.

[Powellrm]

Both HAFS models are back to a cat 5 and imo they've initialized the system best together with HWRF. HMON initialized way too far SW imo and because of that almost makes landfall on Yucatan, disrupting intensification. Even though even the weaker HMON also makes this an intensifying cat 3 nearing landfall, so there are no good scenarios.

I wonder if that is a reflection of dry air being cleared out with a defined core intact, now that it's heading into favorable conditions with a moist environment, low sheer, and high ocean heat content. I wonder if they dipped when the system was not organized quite yet. They still seem extreme, which is not uncommon, but I do believe they portend a rapid strengthening we're about to see.

[Travorum]

One concerning thing I see in the 6z hurricane models is there is much less of an indication of an ERC before landfall. Yesterday's nuclear 12z runs peaked roughly at Tampa's latitude before weakening slightly prior to landfall, while these 6z runs are deepening right up to impact.