GaWx

1. Excellent chance to become a TC imho; strength: likely a H and even a chance for a MH 2. 12Z major ops: -Icon: easily the most threatening of the 12Z runs to the NE Caribbean and perhaps some others later with a H at 180 moving just S of due W at 17N, 50W underneath a strong H5 high -GFS: H recurves way E of Bermuda near 55W -Euro: H recurves 250 miles SE of Bermuda -CMC easily strongest run yet with 992 mb at ~17N, 47W moving WNW but then weakening back to 1005 mb and likely about to recurve E of Bermuda per H5/climo -UKMET like last few runs no TC but still has organized LLC moving WNW to 22N,60W at 192; per H5 and climo, this is likely about to recurve probably meaning a miss of the US but even if so, could threaten Bermuda had this run gone out further -JMA not as threatening as yesterday’s run when it had a TD moving WSW at 14N, 45W at 192; today’s is further N and moving WNW at ~17N, 45W at 192 as a TD; per H5 and climo likely not US threat from there with Bermuda needing to watch it more

Increased +NAO chances this JF on CANSIPS per this:

Thanks, Don. Although the study ended by 2016 (date of article), I was curious about how the theory worked after 2016 for DJF NAO >+1: These are those 4 winters: 2017-8, 2019-20, 2021-2, 2023-4 2017: -2 H hits (AN): works -ACE: ~119 (way AN): works 2019: -2 H hits (AN): works -ACE: 60 (NN): no signal 2021: -1 H hit (NN): no signal -ACE: 75.3 (AN): works 2023: -1 H hit (NN): no signal -ACE: 76.1 (AN): works ———— Summary for these 4 2016+ >1 NAO -# of US H hits through 9/10: worked twice, no signal twice, and didn’t work zero times -ACE through 9/10: worked 3 times, no signal once, and didn’t work zero times -So, for NAO >1: despite not doing well pre-2016 and despite 2020 not working for H hits as the only 2016+ -NAO winter, 2016+ for NAO >1 did much better for both measures with none not working.

Welcome to met. autumn! Please post your September of 2025 observations as well as other current or recent conditions at any location. Unlike the last 2 years, we lucked out in August. We’ll see whether we luck out again this month compared to last year’s horrible Helene. If any moderator sees this, please pin this and unpin the August 2025 obs thread. @buckeyefan1

Now I’ll look at the opposite end: NAO>+1 DJF 1980-1 through 2015-6 1988-9, 1993-4, 1994-5, 1999-00, 2011-2, 2014-5, and 2015-6 1. 1988: -1 H hit (NN): no signal -ACE ~12 (far BN): doesn’t work (major fail) 1993: -1 H hit (NN): no signal -ACE ~33 (BN): doesn’t work 1994: -0 H hits (BN): doesn’t work -ACE ~12 (far BN): doesn’t work (major fail) 1999: -1 H hit (NN): no signal -ACE ~66 (slightly AN): works 2011: -1 H hit (NN): no signal -ACE ~71 (AN): works 2014: -1 H hit (NN): no signal -ACE 21.2 (BN): doesn’t work 2015: -0 H hits (BN): doesn’t work -ACE 26.4 (BN): doesn’t work —————————— Summary for the seven +1+ NAO winters 1980-1 through 2015-6 -# of US H hits through 9/10: no signal 5 times, didn’t work twice, and worked zero times -ACE through 9/10: worked twice and didn’t work five times including two major fails Summary: the seven +1+ NAO cases overall failed to support their theory and actually, if anything, supported the opposite! @donsutherland1@40/70 Benchmark Edit: If I include only the 3 neutral ENSO summers (JJA) (1993, 1994, 2014), that doesn’t help and even makes it worse because none worked for ACE (including one major fail). The one with a signal for # of US H hits didn’t work.

Thanks, Don! The linked article refers to both overall “Atlantic hurricane activity” (ACE-like) and “US hurricane activity”. However, those two things have a decent correlation to each other. So, maybe it works for both. Also, it says as you said that it looks only through “early Sept.” or midpoint of season. So, I’ll assume 9/10 as the cutoff. Out of curiosity because there have been only 5 sub -0.25 DJF NAOs from the early 1980s through the year the article was written (2016), which is the period the article says works best for DJF NAO, I looked at the 5 seasons preceding those winters through Sept 10th. I’m keeping these in mind: -Avg ACE through Sept 10 is ~55 (varies with era) -Avg # of CONUS H hits through Sept 10th 1980-2016 is 0.9 1. 1984-5: -no US H hits through 9/10 (BN): works -ACE through 9/10 was 7.9 (far BN): works 2. 1986-7: -2 US H hits through 9/10 (AN): doesn’t work -ACE through 9/10 was 12.3 (far BN): works 3. 1995-6: -1 US H hit through 9/10 (near avg): no signal to work with -ACE through 9/10 was 153.9 (near record high with only one season, 1933, possibly higher): doesn’t work (major fail) 4. 2009-10: -0 US H hits through 9/10 (BN): works -ACE through 9/10 was 38.8 (slightly BN): works 5. 2010-1: -0 US H hits through 9/10 (BN): works -ACE through 9/10 was 64.6 (slightly AN): doesn’t work —————— So, for these 5 -NAO winters: -# of US H hits through 9/10: worked three times and didn’t work once (1995 had a lack of signal) -ACE through 9/10: worked three times and didn’t work twice (including 1995’s huge fail) ————— Out of curiosity, I checked the 2020 H season because of the 2020-1 -NAO DJF: -3 US H hits through 9/10: doesn’t work -ACE through 9/10 was 50.5 (NN): no signal to work with @40/70 Benchmark@snowman19

Some 0Z models: -GFS has a MH that goes E of Bermuda but then gets blocked by a big high -Like for the 12Z, the 0Z UKMET text has no TC. I’ll see how the maps look when they come out. The 12Z was kind of wacky with two weak lows. -CMC again has a possible TD in the E MDR that weakens later. -0Z JMA goes out only 72 hours. -So, Icon, GFS, UKMET, and CMC are fairly similar at 0Z to their respective 12Z runs. Next up is the all-knowing Euro!

I ended up with ~17.1” of rainfall this month, 225%+ of normal. That’s even more than the 15.33” of last August, when 10.9” fell over a 3 day period from Debby, alone!

Instead of the treadmill, I’ll be taking a walk at the park shortly as a result of mid 60s dewpoints and a nice NE breeze/upper 70s temps.

Today’s 12Z ops are much more active for the E MDR lemon than the runs from 24 hours ago: -Euro has a MH hit Bermuda on 9/14 (fwiw). -GFS has a H pass 250 miles E of Bermuda on 9/13 (fwiw). -ICON has a minimal TS moving ~due W at 180 hours near 16N, 45W. That would be far enough S when also considering its near due W movement and a 600 dam H5 high to its N to be a potential concern for at least the NE Caribbean. -CMC has a TD that later dissipates. -UKMET has two separate weak lows and no TC. I’m throwing this weird solution out since it’s a clear outlier. -JMA has a TD the furthest S of any major model with a TC. It’s at 14N, 45W, and moving WSW (unlike any other model with a TC) at end of its run (192). If that were to be real, it could be a legit concern for the Lesser Antilles and beyond. But all others are up at 16-19N then. And this is the JMA. An outlier JMA, especially to the left, is usually wrong. But we’ll see. @BarryStantonGBP

Followup: As a result of recently formed TS Kiko in the EPAC, 2025 is no longer the quietest Labor Day weekend tropically globally of Joe Bastardi’s lifetime. Why? Going back to 1950: -1980: no TC in EPAC, WPAC, or N Indian. The only TC was TD7 forming 8PM Sun in the NATL and lasting through Mon. Thus, 2025 now having a TS already beats 1980 globally. -1991 is debatable: -no TC in EPAC or N Indian -WPAC had a dissipating Harry, probably down to only a TD, on Sat, and a new TD on Mon -NATL: TD 5 dissipated on Sat -So, unlike 2025, 1991 had no TS+ but there were 3 TDs during the weekend.

Per Joe Bastardi yesterday in the free video, this is and will likely end up being the quietest Labor Day weekend for the globe as a whole tropically (not Atlantic specifically as 2024, for one, was equally quiet) of most of our lifetimes. There was just an Invest in the EPAC and the remnants of a TD in SE Asia. That was it, which is fascinating!

Per Joe Bastardi yesterday in the free video, this is and will likely end up being the quietest Labor Day weekend for the globe as a whole tropically (not Atlantic specifically as 2024, for one, was equally quiet) of most of our lifetimes. There was just an Invest in the EPAC and the remnants of a TD in SE Asia. That was it, which is fascinating!

2025 08 22 2025.640 55 7.1 27 31 2025 08 23 2025.642 75 6.9 25 31 2025 08 24 2025.645 109 8.7 34 41 2025 08 25 2025.648 142 15.2 37 45 2025 08 26 2025.651 192 21.8 36 40 2025 08 27 2025.653 211 23.0 26 33 2025 08 28 2025.656 204 15.8 23 29 2025 08 29 2025.659 209 24.9 31 34 2025 08 30 2025.662 196 18.9 24 30 2025 08 31 2025.664 195 12.7 18 21

I had some rain this morning. The low that gave me that is now offshore. My initial estimate is 0.4”. That puts me at ~17.1” for the month!

Cat5 is the bull’s bull in his posts but he’s right about the 18Z GFS. He’s very consistent to his credit. If his handle were instead TDKaiju, then he’d probably be a bear’s bear. Lazzo, like me, is more neutral and prefers to post without the content being heavily influenced by a bias, bullish or bearish. It’s not easy.

And that’s not surprisingly the area of formation where the EWs have been suggesting would probably be the greatest threat to the US 9/15+ though SC north has a notable threat from the open Atlantic, too: 9/15-21: 9/22-28:

Update on EW from Lazza at S2k: Update on EW vs 2 days ago: slightly quieter 2nd 1/2 but still much more active 2nd half of Sep vs 1st half:1-7: 4.5 (0.3)8-14: 8 (0.5)15-21: 14 (0.9)22-28: 18.5 (1.3)

12Z models: UKMET/GFS/Icon: TD but it then dissipates pretty quickly CMC: just weak low Euro: TD that recurves just offshore NC 9/12: JMA: nada

NYC 50”+: DJF Webb ONI pre 1950/RONI 1950+ 1872-3 CN 1874-5 CN 1898-9 CN 1906-7 CN 1915-6 CN 1916-7 SLN 1922-3 CN 1933-4 MLN 1947-8 WN 1960-1 WN 1966-7 CN 1977-8 WEN 1993-4 WN 1995-6 WLN 2009-10 MEN 2010-1 MLN 2013-4 CN 2014-5 WN 8 CN 4 WN 2 MLN 1 each of SLN, WLN, WEN, MEN 1. CN/WN 12 of 18 (67%) vs only 66 of 156 DJFs (42%). So, chance may have been enhanced by neutral. EN: 2 of 18 (11%) vs 49 of 156 (31%). So, chance may have been decreased by EN. LN: 4 of 18 (22%) vs 41 of 156 (26%)…so, LN may have been pretty neutral influence. 2. 19% of last 32 years 50”+ comparable to 17% of 36 years 1898-9 through 1933-4 @bluewave@donsutherland1

0Z UK NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 120 HOURS FORECAST POSITION AT T+120 : 14.4N 35.2W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 04.09.2025 120 14.4N 35.2W 1012 30 1200UTC 04.09.2025 132 15.2N 36.8W 1012 30 0000UTC 05.09.2025 144 15.8N 38.4W 1012 26 1200UTC 05.09.2025 156 16.8N 40.3W 1012 27 0000UTC 06.09.2025 168 17.5N 42.4W 1013 25

The 87 year old father of one of my best friends passed as a result. My friend and his wife had moved from NO to ATL 30 years earlier. His father and mother were living in a house in N.O. They unfortunately hadn’t evacuated. The water rose so fast! Inside the house, he went under and wasn’t seen by his mother coming back up. There was nothing she could do. They also had a several years old cat, who was nowhere to be seen. She was devastated, but she then needed to save her own life. His mother, then ~76 year old, amazingly survived by (as I recall my friend saying) standing on a wall on the property attached to the house and standing on it for hours (while I think holding on to the adjacent roof to keep her balance if I’m recalling this correctly) until rescuers in a boat could get to her. Can you imagine a 76 year old being strong enough to do that physically and emotionally after what she had just seen happen to her husband of 55 years?! His mother then moved to Atlanta to live with her son/daughter in law. My devastated friend weeks later had to go to N.O. to identify his father’s dead body. Can you imagine how terrible an experience that must have been? That’s not the end of the story. After my friend identified his father’s body and then checked out the totaled house, he starting hearing meows nearby. Lo and behold, it was his parents’ cat, which though malnourished, miraculously survived and was ok!! That cat later came back home to ATL, got back to full health, and lived another 10+ years! His mother lived about another 18 years! Things like this remind me to always be grateful for quiet seasons or at least seasons with few or no landfalls.

That’s a WxBell version of yesterday’s Euro Weeklies that covers 8/28-9/26 of 2025. I prefer to look at the output from the source, itself, ECMWF, as some WxBell maps are of questionable accuracy due to their algos: 9/1-7: slightly BN coastal MA (tan 1st shade is within 10 mm BN or <0.4” BN) and NN inland MA and all of NE 9/8-14: NN MA, slightly BN much of NE 9/15-21: NN 9/22-28: NN These 4 weeks don’t look as dry as the WxBell 30 day map implies. @mitchnick

I was going to post this, but you beat me to it.

0Z UKMET for system leaving Africa over weekend (E MDR lemon): NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 108 HOURSFORECAST POSITION AT T+108 : 13.5N 28.4WLEAD CENTRAL MAXIMUM WINDVERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)-------------- ---- -------- ------------- -------------1200UTC 02.09.2025 108 13.5N 28.4W 1010 310000UTC 03.09.2025 120 14.0N 30.9W 1011 331200UTC 03.09.2025 132 15.9N 31.8W 1010 340000UTC 04.09.2025 144 16.4N 34.6W 1012 281200UTC 04.09.2025 156 17.2N 35.4W 1013 260000UTC 05.09.2025 168 18.4N 36.8W 1013 24