GaWx

0Z Euro: 978 mb at Athens, which is 75 miles E of NHC track/similar to UKMET/GFS/CMC and very close to all-time record low SLP at Athens

0Z Euro: slight E shift of landfall to central Taylor county, notably E of NHC and at 957 mb

0Z UKMET: a bit E of 12Z and a little stronger once again as expected with landfall Big Bend and goes over Athens or 65 miles E of ATL/75 miles E of NHC track HURRICANE HELENE ANALYSED POSITION : 22.8N 86.8W ATCF IDENTIFIER : AL092024 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 26.09.2024 0 22.8N 86.8W 976 52 1200UTC 26.09.2024 12 24.6N 85.7W 972 50 0000UTC 27.09.2024 24 28.6N 84.0W 967 62 1200UTC 27.09.2024 36 34.5N 83.3W 979 37 0000UTC 28.09.2024 48 38.3N 86.9W 985 33 1200UTC 28.09.2024 60 36.7N 87.7W 995 16 0000UTC 29.09.2024 72 37.6N 87.2W 1002 24 1200UTC 29.09.2024 84 37.0N 87.0W 1006 21 0000UTC 30.09.2024 96 37.2N 86.8W 1009 20 1200UTC 30.09.2024 108 CEASED TRACKING

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?

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?

Well fwiw, I roughly estimate that 40% of the 12Z EPS members are over or just W of TLH.

12Z EPS: mean track Gwinnett County, just E of Atlanta. More members just E of ATL vs right over or just W but a decent number are just W. So, a just W of ATL track still a reasonable possibility per 12Z EPS. Many members in high 970s to low 980s when closest to ATL.

I’m taking seriously for sure. Even 940 would be quite serious. But since the hurricane models sometimes overdo the strengthening, I’m hopeful, especially considering the size, that it won’t get as low as they have it

This is a quote from someone at another BB because he worded it so well: “It's bonkers that the NHC track seems to be discounting all of the global models further eastward movement. Not even a mention in any of the discussions. If the NHC nails this track as usual, I'll never doubt them again.” Opinions?

Yeah, I realize that the very large size and very high speed of movement are coming into play to unfortunately minimize how much the winds will come down/SLP rise by the time it gets to N GA (only ~9 hrs later) . I calculated an avg speed of ~28 mph from landfall to N GA, one of the fastest on record for a MH hitting the FL panhandle and moving N. (Eloise of 1975 was ~29). But my hope is that its 920 SLP is way overdone. With it being a very large storm, I’d think it would be difficult for it to get down to 920. Wouldn’t 940 mb be more reasonable considering its size and somewhat limited amount of time before landfall? Also, it temporarily has leveled off. If it is instead 940 mb, perhaps 20 mb could be added to the sub 960 prog for N GA and make it 970s though that would still be very bad and near records.

Considering that the record low SLP for N GA is in the 970s, I’m assuming this is likely way overdone. I sure hope that’s the case. But you never know for sure as this is a very unique situation.

12Z Euro: even stronger vs the 960 of the 6Z with 954 landfall! tracks to just E of Macon and then to Athens

A 2nd batch of heavy showers moving NW off the ocean just came through. There may be a 3rd batch later. This area seems to be on a train track for showers today. None of this has been forecasted earlier by NWS/models. Edit: I ended up with ~2”, none of which had been forecasted by models and the NWS had no mentioned pop til a few hours before. And it turned out I had a little water coming in to my garage on the side that had the most during Debby as well as from the thunderstorm 8/20.

12Z UKMET shifted a little W vs 0Z run’s far NE GA and once again comes in stronger like typical UK trend:TROPICAL STORM HELENE ANALYSED POSITION : 21.5N 86.2WATCF IDENTIFIER : AL092024LEAD CENTRAL MAXIMUM WINDVERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)-------------- ---- -------- ------------- -------------1200UTC 25.09.2024 0 21.5N 86.2W 984 510000UTC 26.09.2024 12 23.1N 86.3W 979 481200UTC 26.09.2024 24 25.5N 85.4W 975 500000UTC 27.09.2024 36 29.6N 83.9W 970 551200UTC 27.09.2024 48 35.6N 84.0W 984 310000UTC 28.09.2024 60 38.7N 86.8W 989 351200UTC 28.09.2024 72 36.9N 89.5W 996 160000UTC 29.09.2024 84 36.6N 89.3W 1003 121200UTC 29.09.2024 96 36.4N 89.3W 1006 100000UTC 30.09.2024 108 CEASED TRACKING

Atlanta’s record low SLP of 981 mb as well as records for much of the W half of GA will certainly be threatened and some if not many will probably be broken. Many current record lows in central GA E to Augusta are from the Storm of the Century of March of 1993. One correction: lowest recorded GA SLP (GA coast is much lower than 970.5) is way too high. It is in the 950s (1890s). But that’s irrelevant for Helene, of course.

I had a heavy batch of showers that came NW off the ocean here the last hour, the heaviest in at least a couple of weeks. The only other significant rain I’ve had this month was 1.5” during 9/5-8. So, since Aug 20th the only significant rains have been today’s and the rain of 9/5-8. I’ll get the measurement later. This was unexpected as there earlier had been no chance of rain and the models didn’t have it. This is important because I finally had a Storm Shield garage door rubber threshold placed yesterday afternoon by company #2 after waiting for several weeks for company #1 to install it to try to prevent future flooding during heavy rain events after what Debby did last month. It requires 48 hours of dry prior to install so the adhesive would be effective. The appointment had been for this afternoon, but fortunately on Mon I was able to move it up to yesterday. Had I not done that, they wouldn’t have been able to install it today in advance of Helene. Whew! It would have been better to not have any rain today to give more time for the adhesive to set in better. But the rain started 19 hours after install. So, hopefully that was enough time.

It looks like the 0Z Euro has the center crossing Gwinnett County in N GA, E/NE of ATL. The distance from landfall position to E of ATL is ~250 miles and it gets there in only 9 hours on the Euro. That works out to an average of a whopping 28 mph, among the fastest on record for that area! To compare, the very fast moving Opal averaged no more than ~25 mph. Eloise of 1975, which also brought damaging winds well inland to W GA, averaged at ~29 mph.

0Z Euro coming in significantly stronger into the Big Bend at 961 mb! It keeps getting stronger with each run.

0Z UKMET: strongest run yet with 977 mb a few hours before a Thu night Apalachee Bay landfall. Keep in mind that this model tends to be conservative this far out. Helene then goes to far NE GA, well E of ATL.

The latest Euro Weeklies mean went absolutely bonkers for the week of 10/7-13. It has a whopping 340% of 2004-2023 averaged ACE or ~23! (see top image below). This is well over peak week climo of 16, which is 4 weeks earlier! This is easily the single highest week I could recall for any single week of Euro Weeklies for the season to date! The 2nd image shows where the bulk of the activity is expected: Gulf, N Caribbean, Bahamas, Bermuda, and much of the W and C subtropical Atlantic. Going back to 1991, I could find only two seasons with ACE anywhere close to 23 during Oct 7-13: -2018’s ~24 due mainly to Leslie and Michael -2016’s ~18 due to Matthew and Nicole So, the latest Weeklies are calling for Oct 7-13 to be just about tied with 2018 for the most active since 1991. That’s very notable for a 100 member ensemble mean. In addition the run’s mean for the week prior, 9/30-10/6 is at 180% of 20 year climo or 17. So, after Helene and the E MDR get ACE up to ~75, an additional 40 is progged for the subsequent two weeks. That would bring ACE up to ~115 with the last half of Oct and Nov still left. The same run is progging another 15 for 10/14-27, which would get it to 130. If this were to verify closely, a 150ish total season ACE would not be far fetched considering the warmth of the Atlantic and the strengthening Niña.

~40 miles E. Nothing unusual this far out.

The spaghetti plots are of the most recent run of these models. AVN is GFS, UK is UKMET, etc

I assume you realize it. But for those who might not realize it, these are not the 18Z global runs, themselves, as they obviously haven’t come out yet. These tracks are mainly based on 12Z runs.

I’m extra worried that the tornado threat from this in especially the NE sector is going to be high. Is that true? Any thoughts? I haven’t heard much about that yet.

12Z Euro ensemble: stronger mean than recent runs; many members are still ~980 mb in Atlanta vicinity, which doesn’t bode well for N GA; flooding rain and wind could both be major issues there; watch out Atlanta, Athens, and surrounding areas. This could rival Opal’s effects there. Combo of strong storm, very fast mover, upper level environment, and large size would be the reasons for this very rare event should it materialize.