GaWx

I can’t make that detailed a call, but that’s the start of prime W Caribbean/Gulf season climowise.

The OHC has recently been cooling substantially after the prior rather steady period: @snowman19you’ll probably like this trend

That first tstorm gave me only a little rain. But a stronger storm is starting now just before 6PM with very gusty winds, heavy rains, and some nearby CTG lightning. SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE CHARLESTON SC 548 PM EDT SUN SEP 7 2025 GAZ118-119-072215- COASTAL CHATHAM GA-INLAND CHATHAM GA- 548 PM EDT SUN SEP 7 2025 ...A STRONG THUNDERSTORM WILL IMPACT CHATHAM COUNTY UNTIL 615 PM EDT... AT 548 PM EDT, DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM OVER HUTCHINSON ISLAND, MOVING SOUTHEAST AT 10 MPH. HAZARD...WIND GUSTS UP TO 50 MPH. SOURCE...RADAR INDICATED. IMPACT...GUSTY WINDS COULD KNOCK DOWN TREE LIMBS AND BLOW AROUND UNSECURED OBJECTS. LOCATIONS IMPACTED INCLUDE... DOWNTOWN SAVANNAH, HUTCHINSON ISLAND, MIDTOWN SAVANNAH, HUNTER ARMY AIRFIELD, WINDSOR FOREST, GARDEN CITY, THUNDERBOLT, SAVANNAH HISTORIC DISTRICT AND SANDFLY. —————— **Edit: I ended up with ~0.90”

MJOwise, alone, 9/7-21/25 is clearly more favorable than 9/7-21/24. But the MJO is just one factor of many. There’s lots of variation of actual outlines within each MJO phase. The MJO is best treated as a guidance tool rather than a crystal ball.

Snowman, the GFS and EPS MJO forecasts (the two best imho) for the next 2 weeks agree that the MJO will remain in the IO and then reverse back to the W Hem/Africa. There’s no MC in sight:

Ray, I graded the Sept ‘24 Euro 2M temp. forecast for DJF 2024-5 an F, the worst Sept winter forecast going back at least to that of Sept of 2017, the furthest back I can find. The Euro averaged ~4F too warm for most of the US! The only area it did well with was the SW. The Sept ‘20 Euro forecast for 20-21 was similarly too warm but not by quite as much (avg of ~3F too warm for the US). OTOH, the Sept forecast for 2023-4 was pretty bad in the other direction with an average miss of ~3F too cold for the US overall. The last good Sept Euro 2M forecasts for the lower 48 as a whole were for 2021-2 and 2019-20. The avg miss in the NE was very small.

3:25PM: I’m getting a thunderstorm now, the first rain here this month.

Barry, I don’t know why JB is saying that. The Sept 2025 MJO (first 7 days plus 2 week forecast through 9/21) looks nothing like 2024! Sept 2025: -GEFS: lower to moderate amplitude 2, 3, 2, 1, 8, which is actually favorable -EPS: lower to moderate amplitude 2, 3, 2, 1, 8, which is actually favorable Sept 1-21 of 2024 (blue): moderate to high amplitude 4, 5, 6 (not usually favorable unlike what we now have) was like night and day vs 2025: Perhaps JB is looking further ahead to late Sept-Oct. Regardless, he wants lots of clicks!

9/7/2015 (see below) was the last 9/7 TWO with no new TCG being considered. However, that was going into a strong El Niño, there was TS Grace then in existence in the E MDR, and the outlooks then went out only 5 rather than 7 days. Also, this TWO failed to see a new TD (which lead to Henri) that formed 9/8-9 in the subtropics: TROPICAL WEATHER OUTLOOK NWS NATIONAL HURRICANE CENTER MIAMI FL 800 AM EDT MON SEP 7 2015 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: The National Hurricane Center is issuing advisories on Tropical Storm Grace, located several hundred miles west-southwest of the Cape Verde Islands. Tropical cyclone formation is not expected during the next 5 days. $$ Forecaster Pasch https://www.nhc.noaa.gov/archive/xgtwo_5day/gtwo_archive.php?current_issuance=201509071437&basin=atlc&fdays=2

1. Indeed. The Sept Euro fcast for the NE DJF anomaly is for an avg of only ~+1.8 F. 2. But that is almost as warm as any Sept fcast for the NE DJF of the last 9 with it just slightly colder than 24-5’s ~+2.0 F and near 22-3, 20-1, and 19-20’s +1.8 F. 3. How has the Sept Euro verified vs actual for La Niña in the NE? I’ll look at NYC: For NYC using 1991-2020 avgs for the 5 Nina winters since 2017-8: -24-5 ended up -1.4 F vs ~+2F Sept Euro fcast or ~3.4 F colder than Euro -22-3 ended up +5F vs Euro ~+1.8F fcast or ~3.2F warmer than Euro -21-2 ended up +1.1F vs Euro ~+0.4F fcast or ~0.7F warmer than Euro -20-1 ended up 0.0F vs Euro +1.8F fcast or 1.8F colder than Euro -17-8 ended up +0.2F vs Euro +0.9F or 0.7F colder than Euro So, for the 5 Niña winters since 17-8, the Sept Euro turned out to be in F: 3.4 too warm, 3.2 too cold, 0.7 too cold, 1.8 too warm, and 0.7 too warm or an avg of 0.4 too warm

The 18Z GEFS is the most active run yet in the W Car/Gulf 9/12-end of the run! If I were living on the Gulf coast, I’d be a bit concerned. As Barry earlier mentioned, this has strong support from the MJO. More about that soon:

Regarding all 9 Euro DJF fcasts issued in Sept since 2017-8 (as far back as can be seen at the Euro site), there wasn’t even a tiny speck of BN anywhere in the lower 48 E of 110W long. The only one that had any BN anywhere in the lower 48 was the 2019-20 fcast, which had a small area of ~-1F in a small part of the Mtn W (which amazingly enough ended up being the only area with BN): Despite that, there were notable areas of actual BN in portions of the lower 48 in all of these DJFs except 2019-20 and 2023-4. So, your statement ECM is now incapable of seeing below normal temps has essentially been true for its Sept fcasts since 2017-8. However, two of its 8 Oct fcasts and one of its Nov fcasts for DJF did have some BN: Oct ‘23, which failed as there was no BN in the lower 48: Oct ‘18, which got the BN in KS right but the rest of this BN area ended up NN or AN and also it missed the widespread BN in NW 1/2 of the US: Nov ‘17 in UP of Mich, which was correct, but it missed the widespread BN in the Midwest, Plains, and N Rockies:

Here are the Sept Euro forecasts for DJF 2024-5 back to 2017-8 vs actual 2024-5 prog: avg 4F too warm much of US but SW close; grade: F 2024-5 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2024&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2023-4 prog: MW 5-8 too cold, NE 3-4 too cold, SE 1-3 too cold, W close; grade D 2023-4 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2023&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2022-3 prog: W MW 3 too warm; E MW and NE 3 too cold, SE 1-2 too cold, W 6 too warm; grade D 2022-3 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2022&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2021-2 prog: pretty close except 2 too warm W; grade A 2021-2 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2021&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2020-1 prog: 0-4 too warm MW, 3 too warm NE/SE, SC 4-6 too warm, W 1-2 too warm; Grade D 2020-1 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2020&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2019-20 prog: MW 2 too cold, NE close; SE 2-3 too cold, W 0-2 too cold; grade A 2019-20 actual: https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2019&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2018-9 prog: MW 1 too warm, NE close, SE 2-3 too cold, W 2-3 too warm; grade B 2018-9 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2018&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot 2017-8 prog: MW 3 too warm, NE 2 too warm, SE/W close; Grade C 2017-8 actual https://psl.noaa.gov/cgi-bin/data/usclimdivs/climdiv.pl?variab=Temperature&type=1&base=7&mon1=12&mon2=2&iy[1]=2017&iy[2]=&iy[3]=&iy[4]=&iy[5]=&iy[6]=&iy[7]=&iy[8]=&iy[9]=&iy[10]=&iy[11]=&iy[12]=&iy[13]=&iy[14]=&iy[15]=&iy[16]=&iy[17]=&iy[18]=&iy[19]=&iy[20]=&iy[21]=&iy[22]=&iy[23]=&iy[24]=&iy[25]=&iy[26]=&iy[27]=&iy[28]=&iy[29]=&iy[30]=&irange1=&irange2=&xlow=-10&xhi=10&xint=1&iunits=1&scale=100&iwhite=1&iswitch=0&Submit=Create+Plot ——————— -GPA: 2.0 -Last 3 poor -Best 2019-20 and 2021-2; worst 2024-5 -2 A, 1 B, 1 C, 3 D, 1 F -The Sept ‘25 fcast for 2025-6 is for US as a whole the 2nd warmest to 2024-5 since 2017-8 -NE prog misses: +4, -3.5, -3, 0, +3, 0, 0, +2; so, NE prog was too warm thrice, too cold twice, and close thrice; So, NE prog on avg was only 0.3 F too warm vs actual meaning negligible bias vs actual though avg miss was by ~2 F -MW prog misses: +4, -6.5, 0, 0, +2, -2, +1, +3; so, MW prog was too warm 4 times, too cold twice, and close twice; So, MW prog on avg was only 0.2 F too warm meaning negligible bias vs actual though avg miss was by ~2 F -SE prog misses: +4, -2, -1.5, 0, +3, -2.5, -2.5, 0; so, SE prog was too warm twice, too cold 4 times, and close twice; So, SE prog on avg was only 0.2 F too cool vs actual meaning negligible bias vs actual though avg miss was by ~2 F -W prog misses: +2, 0, +6, +2, +1.5, -1, +2.5, 0; so, W prog was too warm 5 times, too cold once, and close twice; So, W prog on avg was 1.6 F too warm! Thus, there appears to be a notable Euro warm bias for the W for winter at least in Sept progs. Avg miss was ~2 F

I just found Sept 2M forecasts for Dec and Jan individually though not Sept for DJF: https://charts.ecmwf.int/products/seasonal_system5_standard_2mtm?area=NAME&base_time=202509010000&stats=ensm&valid_time=202510020000 @donsutherland1@mitchnick

In addition: The last few GEFS and EPS runs have forecasted MJO in the relatively favorable phases of 2, 1, and 8 through Sept. 19 and this would probably extend at least through the rest of Sept per longer term model guidance and climo:

Do you or does anyone else have a link that can be provided to past years’ Euro Sept 2m temperature forecasts going back however far they do for the respective upcoming DJFs for North America or the US? Edit: I found it kind of sort of. See post below. @donsutherland1@mitchnick

The new Euro has DJF Nino 3.4 much cooler than last month with it at ~-0.50 vs last month’s -0.08: 8/1/25 Euro prog for DJF: -0.08 9/1/25 Euro prog for DJF: ~-0.50

The last few GEFS and EPS runs have forecasted MJO in the relatively favorable phases of 2, 1, and 8 through Sept. 19 and this would probably extend through at least the rest of Sept per longer term model guidance and climo:

Thanks, Don. As I assume you realize, crop sizes have overall so far actually been aided rather than hurt by increased CO2: -GW has lead to longer average growing seasons thus increasing avg crop sizes. -Related to this, the increase in avg growing season lengths has allowed crops to be grown further north than in the past. -There’s now increased CO2 for plants to thrive better (the “CO2 fertilization effect”). -At least partially related to this improved environment, the Midwest has had a decrease in the frequency of widespread droughts since the 1990s. Thus, I suspect that one of the reasons that CC isn’t being treated as a major crisis by as many as you’d want is that it has actually lead to more favorable rather than less favorable conditions for food supply, one of the biggest essentials to support animal life. That’s a huge benefit for life on our planet. So CC, though very bad for rising sea level, increased frequency and severity of major flooding events, increased frequency of severe TCs, increased coral bleaching, and an increase in extreme heat related casualties, hasn’t been all bad news by any means. To minimize the major benefit to food supply as well as a decline in extreme cold related casualties would not be considering the full effect of CC.

Nobody knows, which is what makes forecasting discussions so interesting. For comparison purposes, here are some very quiet periods during climo active dates of other non-El Nino seasons during the current active era: -In 2024, there were 0 TCs during the 19 days 8/21-9/8. -In 2022, there were 0 TCs in August. -In 2016, there were 0 TCs Sep 4-11 and 0 H Sep 3-28. -In 2013, there was no H til 9/11. -In 2001, there was no H til 9/8 ———- Back to 91L: 12Z Euro has no TC from this in the MDR although something forms later in the subtropics. So, the highly unreliable JMA, especially when it’s on its own, is the line holdout of this cycle for a TC in the tropics from this. Edit: For record-keeping purposes now that the rest of the run has been released, the 12Z JMA is a bit slower than the prior two. But it still has a similar idea of an early recurve with a H moving N along 60W 144-192.

12Z rundown so far: Icon and GFS have almost nothing unlike recent runs. CMC is so far (through 78) coming in much weaker with no closed LLC. UKMET once again has no TC. Edit: But fwiw JMA still has it in the MDR at 72 (1008 mb TC):

Indeed, Mitch! Check out this poor CANSIPS ENSO verification: 8/31/24 run for Aug ‘25 had Modoki Niño look 7/31/25 run for Aug ‘25 asks “what Modoki Nino?”

It’s very hard to predict with confidence how the upcoming winter will be this far out. But I will say that pretty close to normal temperatures (based on 1991-2020 averages) in your area (NE US) are quite possible this DJF.

Thanks. Over the longer term and including all months, ~40% of TCs passing near the Virgin Islands later hit the Conus. The % is probably highest in Jul/Aug/first half of Sept.

From something well to the W of 91L coming out of the Caribbean in 6-7 days, the 6Z GEFS is pretty active mainly in the Gulf with a couple E of FL. Some of these members are hurricanes. *Edit: The GEFS/EPS of the last few days have had the MJO then in or near the most dangerous phase for July-Sept CONUS H hits, phase 2: Edit: 6Z GEFS suggests there could be another TC coming out of the W Caribbean later.