GaWx

The 0Z UKMET has a new TC forming in the far SE MDR at hour 78. This is for the AEW following the current E MDR orange. What's notable about it is that it is quite aggressive considering how conservative it usually is. It has it down to 999 mb at 168 hours at 12.9N, 40.7W, moving steadily WNW. That means it could threaten the LAs in 10 days. What should be concerning to the LAs is that the Euro has something similar along with notable members on the last several EPS runs. In addition, the GFS, CMC, and ICON have it though it looks to recurve on those: 0Z UKMET NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 78 HOURS FORECAST POSITION AT T+ 78 : 9.7N 15.4W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 02.09.2023 84 10.3N 17.7W 1007 46 0000UTC 03.09.2023 96 10.9N 19.0W 1007 34 1200UTC 03.09.2023 108 12.1N 22.9W 1008 30 0000UTC 04.09.2023 120 11.6N 26.7W 1008 28 1200UTC 04.09.2023 132 11.7N 30.9W 1007 35 0000UTC 05.09.2023 144 11.7N 34.9W 1004 36 1200UTC 05.09.2023 156 12.2N 38.1W 1001 38 0000UTC 06.09.2023 168 12.9N 40.7W 999 46

-0Z CMC as expected in correction mode shifted vs the 12Z to the right significantly (~50 miles) to far NW Taylor County -0Z ICON vs 18Z shifted very slightly left (~5 miles) to SE Taylor County -0Z GFS vs 18Z shifted left 15 miles into far NW Taylor County -0Z UKMET about same as 18Z in south central Taylor County -0Z Euro vs 12Z shifted 20 miles right to C Taylor County *Edited to add Euro

The more reliable models are pretty tightly centered on Taylor County, FL, landfall centered on ~9AM EDT. Then tracks go mainly just inland from Savannah, which is about the worst possible track regarding winds. Also, high tide there, which is an astronomical high tide due to perigee and full moon, is at 8:30PM, which is near the time of the center being closest.

Taylor County is best bet per models. But it has ~45 miles on the Gulf. So, pretty large. And a lot of swamp/marsh. Good luck with that!

Nearly unanimous Taylor County landfall centered on ~9AM EDT. Then it tracks go mainly just inland from Savannah, which is about the worst possible track in terms of winds. Also, high tide there is an astronomical high tide due to perigee and full moon and it's at 8:30PM, which is near the time of the center being closest.

18z UKMET has like the 18Z Euro shifted its landfall 15 miles SE along with the remaining SE US track. The 12Z UK landfall was in C Taylor Cty and the 18Z is in S Taylor Cty. Also, 18Z landfalls 2.5 hours sooner (7:30AM) vs 10AM on 12Z.

~15 mile SE change in track vs 12Z Euro. Landfall still in Taylor county but central rather than NW. Entire track inland is similarly shifted slightly SE.

ACE has risen to 39, slightly higher than the 30 year average for the date. Aside: As the tropics get very active, you know who gets quiet. Same pattern most every time. That strategy helps make him/her effective.

I see 1896 and 1950 but not 1985 for Cedar Key landfall: https://www.nhc.noaa.gov/data/tracks/tracks-at-1985.png

Idalia is forecasted to heavily affect a large portion of the SE. In some areas even away from the FL Big Bend that are near the track, it will very likely end up as the most impactful wx event in many years. Moderators, please pin this. Thanks

-Only 6 (14%) of the last 44 winters had a -NAO vs 12 (27%) neutral and 26 (59%) +NAO. Also, only one of the last 12 winters was -NAO. However, a good portion of neutral and even some of the +NAO winters had a solid -NAO month. That's the better hope if you want -NAO. -So, for whatever reason, we're in a +NAO winter era of sorts. Until we get passed it, it won't be easy to have -NAO dominate in any one winter. - Average monthly sunspots for these six -NAO winters were all low to very low: 20, 6, 12, 22, 33, and 14 for an average of only 18. This 18 compares to the longtime average monthly sunspots of 85 (based on 1900-2022 data). So, none of these six low sunspot #s are anywhere near the quite high 150+ that we're likely headed toward this winter and they're not even close to the 85 average. -All six -NAO winters were within two years of a solar min whereas we're going to be much closer to a solar max than min this winter. -So, I'm betting pretty heavily on either a +NAO or neutral NAO averaged over this winter with the hope for one solid -NAO month. I'd take that one month and run.

From 5PM NHC discussion: "This has resulted in a westward shift of about 20-25 n mi compared to the previous forecast" This makes sense based on 12Z model consensus.

Ouch! Hurricane watch GA and lower SC coast. Hope this is overdone but it has been a worry. Hopefully the struggles of the storm that have been mentioned here are actually going to keep it from reaching major status. But it isn't looking good right now.

Maybe this won't end up as a major H landfall. Fingers crossed! Perhaps their climo says that there are geographic factors that make it extremely difficult and that that will come into play for Idalia. Thoughts?

1. Indeed, the 12Z CMC is outside the cone although for the record it's ~50 rather than 100 miles outside of it. The 12Z CMC is at Apalachicola while left side of cone is at Alligator Point, 50 miles E. But it is notable that it's outside the cone. 2. One of the issues is that Idalia's cone is rather narrow (~100 miles wide at FL coast). To compare, here was Ian's cone then, which was a bit wider: https://www.nhc.noaa.gov/archive/2022/IAN_graphics.php?product=3day_cone_with_line_and_wind 2. Now I'll address the CMC's horrible left bias regarding Ian, which made landfall near Port Charlotte at 19Z on 9/28/22. Here were the 12Z 9/27 runs for Ian: ICON Port Charlotte CMC Tampa GFS just N of Port Charlotte Euro Port Charlotte UKMET 20 miles S of Ft. Myers Note that CMC was still up at Tampa, which is 70 miles to the north/left of the actual Ian landfall that occurred just 31 hours later. IF Idalia were to make landfall 70 miles to the right of today's 12Z CMC, that would be well within the cone. Also, keep in mind that the prior CMC run (0Z 9/27) was way up in the Big Bend, or ~200 miles away from actual landfall! So, the CMC appears to have a severe left bias. 3. The 12Z GFS is on the left edge of cone (Alligator Point). The 12Z Euro is in W Taylor County or ~25 miles E of the GFS/~25 miles W of the cone's center. The 12Z ICON/UKMET are in mid Taylor Count ~15 miles E of Euro or ~10 miles left of mid-cone. To summarize the 12Z runs: -CMC 50 mi left of cone's left edge -GFS left cone edge/50 mi left of cone center -Euro 25 mi left of cone center -UKMET/ICON 10 mi left of cone center -So, all five left of cone center -So, 12Z runs favor moving cone a bit to the left at 5PM advisory.

Isn't it more like 32 hours from now til landfall rather than 48 hours?

0Z UKMET: after the 12Z UKMET had a 65 mile NW shift to Apalachee Bay, the 0Z is similar with no more than a slight E adjustment. So, most of the 12Z 65 mile NW shift is retained on the 0Z: TROPICAL STORM IDALIA ANALYSED POSITION : 21.8N 85.1W ATCF IDENTIFIER : AL102023 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 29.08.2023 0 21.8N 85.1W 994 50 1200UTC 29.08.2023 12 23.6N 84.8W 993 51 0000UTC 30.08.2023 24 26.4N 85.1W 991 43 1200UTC 30.08.2023 36 29.2N 84.4W 987 47 0000UTC 31.08.2023 48 32.1N 82.5W 989 41 1200UTC 31.08.2023 60 34.0N 79.7W 994 40 0000UTC 01.09.2023 72 34.4N 76.0W 999 38 1200UTC 01.09.2023 84 34.2N 73.4W 1003 43 0000UTC 02.09.2023 96 33.4N 71.2W 1006 37 1200UTC 02.09.2023 108 30.8N 71.2W 1007 34 0000UTC 03.09.2023 120 30.9N 70.6W 1007 30 1200UTC 03.09.2023 132 30.3N 71.6W 1008 27 0000UTC 04.09.2023 144 30.2N 72.0W 1008 26 1200UTC 04.09.2023 156 CEASED TRACKING

0Z 9/26/22 runs: (Ian made landfall Port Charlotte area at 13Z on 9/28/22) ICON Venice CMC Apalachee Bay GFS Apalachee Bay Euro Cedar Key UKMET Port Charlotte

But unlike for Ian, the GFS isn't 250 miles NW of the UKMET. The model agreement is much better for Idalia.

But your point is still a good one. No major in that region in 73 years means increased vulnerability if a major were to hit there.

You may be forgetting Easy of 1950, which hit Cedar Key as a cat 3.

No offense but I'd plan to come at another time without hesitation.

Not meaning to scare anyone and for those who were unaware, Tampa Bay supposedly had as much as a 15 foot surge 9/25/1848 assuming accurate records! It appears that was from either a strong cat 3 or more likely a cat 4 with its 945 mb center moving ENE into Clearwater. Tampa, which was then just a small village of <200, measured 954 mb. This is pretty much the worst case scenario that would require everything to go wrong (very strong storm, center landfall very close, large size, angle/speed of approach, etc) and I'd hope that it is no more than a one in several hundred year event on average: https://baynews9.com/fl/tampa/news/2012/9/25/great_gale_of_1948

So, regarding the 12Z runs vs 0Z runs in summary for FL landfall, 4 of 5 shifted NW/left (though mainly slight other than UKMET's 65 mile shift) while the CMC is the lone model that shifted SE/right a bit.

12Z Euro is ~20 miles NW of 0Z Euro landfall, which was ~30 miles NW of Cedar Key. So, now ~50 miles NW of Cedar Key. It landfalls at ~10 AM Wednesday vs ~8AM Wednesday. And as I said significantly stronger with ~970 mb on 12Z Euro vs 987 mb on 0Z.