GaWx

The 12Z JMA once again refuses to recurve 96L. It keeps it weak (TDish) and it hits ~Vero Beach, FL, as a 1011 TD at 192 (8/15). Due to ridging to its N, it is moving mainly W and toward the Gulf. This is a far left outlier, which sometimes happens with the JMA.(The weak low near Barbados is from the W African wave.)

W African AEW: 1. The 12Z ICON is slightly stronger than the 0Z with the W African AEW. At 180, it has what already looks like a TD (well organized 1008 mb low at 19N, 46W. Although a TC near that position often recurves safely, this one is turning back to just N of due W after moving WNW earlier due to a stronger high to its north at this longitude. 2. The 12Z UKMET doesn’t have this. However, the 0Z had this data, which likely is not from the same AEW: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 114 HOURS FORECAST POSITION AT T+114 : 15.4N 18.6W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 12.08.2025 120 15.6N 21.0W 1009 28 1200UTC 12.08.2025 132 15.0N 24.0W 1010 27 0000UTC 13.08.2025 144 15.4N 26.0W 1010 23 1200UTC 13.08.2025 156 CEASED TRACKING

“Prediction remains on track for above-normal Atlantic hurricane season” Forecasters from NOAA’s National Weather Service updated the number of expected named storms to 13-18 (with winds of 39 mph or greater), of which 5-9 could become hurricanes (winds of 74 mph or greater), including 2-5 major hurricanes (winds of 111 mph or greater). The adjusted ranges are for the entire season from June 1 though November 30, and are inclusive of the four named tropical storms that have already formed. In the Atlantic basin, a typical hurricane season will yield 14 named storms, of which seven become hurricanes and three become major hurricanes. The likelihood of above-normal activity is 50%, a 35% chance of a near-normal season, and a 15% chance of a below-normal season. This updated prediction is similar to the initial outlook issued in May. https://www.noaa.gov/news-release/prediction-remains-on-track-for-above-normal-atlantic-hurricane-season —————— I’ve never been a fan of these wide ranges, especially 2-5 MH in this case, but otherwise I appreciate the availability of their predictions.

I think that’s a good guideline, but I feel there are exceptions. For example, due to good model support (most importantly including ensembles) for a strong western Atlantic hurricane from it, I feel that the thread for the AEW still in W Africa, despite it not yet being an invest and it not even being on the TWO, is already easily warranted. It will almost definitely be made an Invest and will make the TWO soon. I just posted the rather ominous looking 6Z Euro ensemble for it. I see no problem with already having posts about it siphoned off to its own thread so as to allow this main thread to not be as cluttered. Also, should it end up being a storm, we’d then have posts from further back in time all in one thread to look back at to see how it evolved on the models early on.

Since Atlantic ACE is considered to be a winter forecast factor: TSR just updated their forecast from last month…. -ACE increased markedly from 126 to 144. This compares to the CSU’s 145 and the Euro seasonal’s ~155. -The # of NS/H/MH increased slightly from 15/7/3 to 16/8/3. -However, US impacts remained the same at 4 NS/2 H. https://www.tropicalstormrisk.com/docs/TSRATLForecastAugust2025.pdf

TSR just updated their forecast from last month: -ACE increased markedly from 126 to 144. This compares to the CSU’s 145 and the Euro seasonal’s ~155. -The # of NS/H/MH increased slightly from 15/7/3 to 16/8/3. -However, US impacts remained the same at 4 NS/2 H. https://www.tropicalstormrisk.com/docs/TSRATLForecastAugust2025.pdf

The 6Z Euro ens 144 hour (end of run) is more active and quite possibly the most active run yet with this AEW. I count 19 closed sfc lows with 4 of those being sub 1000 mb. This is unfortunately setting up to be a potentially very dangerous system down the road for some land areas and is something the Euro Weeklies have been on top of for at least the last 9 days. For the Conus, itself, I’ll especially be interested in whether or not the MJO is going to be either in or nearby phase 2 (inside or outside the circle), the most dangerous phase per the last 50 years of tracks, around two weeks from now. Model consensus is at least hinting at that possibility.

2025 ACE, which is now 3.5, has just moved ahead of both 1998 and 1999 as of this date. Neither of those years had another storm til Aug 18/19. And yet they each ended up with ACE of 181 and 176, respectively. I’m not predicting that’s going to happen again. But I am saying that it isn’t a remote possibility that the season end up active (say 140+) just because it was only at 3.5 as of 8/6. Edit: Fwiw in the spring I predicted a slightly above 1991-2020 avg of 139 for 2025 ACE in the contest, and I wouldn’t change that even if I could.

A small thunderstorm has just popped up overhead this evening. I can’t tell if this is likely going to amount to much. I heard one clap of thunder. Temp is 80. Edit 8:25PM: That cell amounted to about nothing. However, it suddenly started raining heavily at 8:20 PM soon after a new 75 mile long SW to NE line of very heavy showers had just popped up with my area on the NE edge. It’s pouring! Edit: It poured for only a short period the evening of August 6th. Thus, I ended up with only ~.0.25” for the day, putting me at 5.25” for 8/1-6!

Now that the GFS has finally caved, the JMA is now about the lone holdout of the major globals and is consistent with the last two days of its 12Z (extended) runs. The 12Z has it near 26N, 75W, or ~100 miles NE of the central Bahamas as a 994 mb high end TS . It is just then moving WNW to NW and starting a recurve. Regardless, it doesn’t appear to be a safe recurve for the US E coast. With the JMA now being the lone main operational global outlier and with very few members like this from the major ensemble runs, this is very likely wrong. I remember times when it was a far left outlier and ended up dead wrong.

CSU 8/6/25 update: 145 total ACE vs 140 in last month’s forecast, vs 122, which is 1991-2020 average, and vs the new Euro seasonal’s ~155: FORECAST OF ATLANTIC SEASONAL HURRICANE ACTIVITY AND LANDFALL STRIKE PROBABILITY FOR 2025 We have maintained our forecast for a slightly above-normal 2025 Atlantic basin hurricane season, although noting lower-than-normal confidence with this outlook. Sea surface temperatures across the eastern and central Atlantic have anomalously warmed over the past few weeks and are now somewhat warmer than normal. Multiple indicators anticipate likely cool ENSO neutral conditions during the peak of the Atlantic hurricane season. Warm sea surface temperatures and ENSO neutral conditions typically provide a more conducive dynamic and thermodynamic environment for hurricane formation and intensification. The primary reason for the uncertainty in the outlook is the high observed Caribbean shear over recent weeks. Typically, high levels of Caribbean shear in June July are associated with less active hurricane seasons. We anticipate a slightly above- average probability for major hurricanes making landfall along the continental United States coastline and in the Caribbean for the remainder of the hurricane season.

CSU 8/6/25 update: 145 total ACE vs 140 in last month’s forecast and 122, which is 1991-2020 avg, and the new Euro seasonal’s ~155: FORECAST OF ATLANTIC SEASONAL HURRICANE ACTIVITY AND LANDFALL STRIKE PROBABILITY FOR 2025 We have maintained our forecast for a slightly above-normal 2025 Atlantic basin hurricane season, although noting lower-than-normal confidence with this outlook. Sea surface temperatures across the eastern and central Atlantic have anomalously warmed over the past few weeks and are now somewhat warmer than normal. Multiple indicators anticipate likely cool ENSO neutral conditions during the peak of the Atlantic hurricane season. Warm sea surface temperatures and ENSO neutral conditions typically provide a more conducive dynamic and thermodynamic environment for hurricane formation and intensification. The primary reason for the uncertainty in the outlook is the high observed Caribbean shear over recent weeks. Typically, high levels of Caribbean shear in June July are associated with less active hurricane seasons. We anticipate a slightly above- average probability for major hurricanes making landfall along the continental United States coastline and in the Caribbean for the remainder of the hurricane season.

The latest Euro Weeklies (yesterday’s run) remain quite active vs active 20 year climo base ACE (>200%) through ~8/24. Then they cool down to close to active avg 8/25-31 (100%). The first stab at 9/1-7 is slightly below the active climo (80%). I wonder if this is MJO related. Regarding absolute ACE, the very active Aug 18-24 is the most active week through Sept 7. As per what I’ve recently posted, the EW progs did fairly well in general last year overall looking out several weeks when they were consistent for, say, 7 days in a row. They’ve been consistent regarding well above 20 year climo levels of activity for 8/11-8/24 for at least that long. Regarding 8/25-31, they’ve been near that 20 year climo for 3 runs. So, I still want to see how the rest of this week’s runs look before giving too much weight to its 8/25-31. Of course, 9/1-7 is a total crap-shoot right now with that slightly below 20 year climo being just its first prog.

Dexter has about another day or so as a tropical system. It is currently experiencing strong vertical wind shear, which is only expected to increase during the next 24 to 48 h. However, models continue to predict that the interaction with the trough to north in the next day or so should strengthen Dexter while it undergoes extratropical transition. It should be noted that during the extratropical phase of the forecast, there is quite a bit of spread in the intensity guidance. Several models during the 36 to 60 h time frame show the cyclone reaching hurricane-force. The NHC intensity forecast has been raised to a peak of 60 kt at 48 h, very near the corrected consensus aid, HCCA. **There remains the possibility that upward adjustments in the intensity forecast could be need in future advisories.** FORECAST POSITIONS AND MAX WINDS INIT 06/0900Z 39.4N 59.9W 40 KT 45 MPH 12H 06/1800Z 39.8N 57.7W 45 KT 50 MPH 24H 07/0600Z 40.6N 54.1W 50 KT 60 MPH 36H 07/1800Z 41.9N 50.1W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 08/0600Z 43.2N 46.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 60H 08/1800Z 44.5N 42.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 09/0600Z 45.2N 38.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 10/0600Z 46.0N 30.1W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 11/0600Z...DISSIPATED $$ Forecaster Bucci

1. The GFS continues as of today’s Happy Hour run to not safely recurve this as it grazes the Conus E coast from NC to ME followed by a direct hit on Nova Scotia. The storm then goes into Newfoundland. 2. The 12Z JMA once again also doesn’t recurve this. It has it just N of PR moving WNW at the end (192 hrs). 3. Barry, you may want to update the thread title to E MDR AOI or something similar because there’s another in Africa not too far behind. Thanks.

Strong thunderstorms here moving in now! It looks like twilight! ..A STRONG THUNDERSTORM WILL IMPACT EFFINGHAM JASPER AND CHATHAM COUNTIES UNTIL 530 PM EDT... AT 453 PM EDT, DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM OVER BLOOMINGDALE, MOVING NORTHEAST AT 5 MPH. HAZARD...WIND GUSTS OF 50 TO 55 MPH. SOURCE...RADAR INDICATED. IMPACT...GUSTY WINDS COULD KNOCK DOWN TREE LIMBS AND BLOW AROUND UNSECURED OBJECTS. LOCATIONS IMPACTED INCLUDE... POOLER, RICHMOND HILL, SAVANNAH INTERNATIONAL AIRPORT, GODLEY STATION, I-16/I-95 INTERCHANGE, DOWNTOWN SAVANNAH, HUTCHINSON ISLAND, RINCON, GARDEN CITY AND PORT WENTWORTH. ———— .***Upgraded to severe:BULLETIN - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WARNING NATIONAL WEATHER SERVICE CHARLESTON SC 508 PM EDT TUE AUG 5 2025 THE NATIONAL WEATHER SERVICE IN CHARLESTON HAS ISSUED A * SEVERE THUNDERSTORM WARNING FOR PORTIONS OF... CHATHAM COUNTY IN SOUTHEASTERN GEORGIA... EFFINGHAM COUNTY IN SOUTHEASTERN GEORGIA... JASPER COUNTY IN SOUTHEASTERN SOUTH CAROLINA... * UNTIL 615 PM EDT. * AT 508 PM EDT, A SEVERE THUNDERSTORM WAS LOCATED OVER POOLER, MOVING NORTHEAST AT 10 MPH. HAZARD...60 MPH WIND GUSTS. SOURCE...RADAR INDICATED. IMPACT...EXPECT DAMAGE TO ROOFS, SIDING, AND TREES. * LOCATIONS IMPACTED INCLUDE... POOLER, SAVANNAH INTERNATIONAL AIRPORT, I-16/I-95 INTERCHANGE, GODLEY STATION, DOWNTOWN SAVANNAH, HUNTER ARMY AIRFIELD, HUTCHINSON ISLAND, WINDSOR FOREST, MIDTOWN SAVANNAH AND COFFEE BLUFF. ———- Edit: I ended up with ~0.4” from this severe thunderstorm on Aug 5, which brings my Aug 1-5 rainfall up to a whopping 5”! The CTG lightning was frequent. Highest wind gusts likely exceeded 40 mph. The Pooler area of Chatham county (NW of here) was harder hit with flooding rains as high as ~3” in spots, highest wind gust at 60 mph at KSAV, and even some pea sized hail!

The BoM released 8/2/25 has -0.2 for ASO and then rises to near 0.0 for the winter: Colder boat needed here too probably.

Thanks, Mitch. This is slightly cooler than the July run, which had ~-0.1 (ASO through NDJ): This new one has ~-0.3 for August and has trimonths through DJF at ~-0.2. So, it’s ~steady from now through winter though it still tends to have a bit of a warm bias even this late. The implied RONI low would be ~~-0.5 ignoring this warm bias. @Stormchaserchuck1

1. The 12Z GFS has this hit near Cape Canaveral on 8/16 as a ~cat 1 H. 2. The 12Z Euro like recent runs and has this as no more than a weak sfc low. It then recurves the weak disturbance safely well out in the ocean. So, it is totally disagreeing with the GFS’ FL hit. Edit: the EPS (as well as AI and its ensembles) agree with the Euro op.

Lol, Aug-Nov doesn’t need to be anywhere near the most active ever to get 2025 to ~155 ACE and certainly wouldn’t even require close to 2005’s ACE the rest of the way, which was 179. We’re now at 2.5, which means 152.5 is needed to get to 155. 2005/1998/99/2017/2004/1961/1995 had 179/178/173/220/216/177/207 more ACE still to go. So, the most active the rest of the season since 1951 (2017’s 220, 2004’s 216, and 1995’s 207) would be 55-67 higher than the 152.5 needed this year to get to 155. Where are you getting your info?

Chuck, I didn’t look at ENSO yet.

Maybe but not just the finish. The Weeklies have quite an active August.

Since ACE is discussed here as a winter forecast factor, the new Euro monthly seasonal forecast has substantially increased from the near 30 year normal of last month’s forecast, which had ~125 ACE, to today’s ~155. The 155 incorporates the 1.5 prior to August, the well AN ~40 that the latest Weeklies have for August, and the well AN 130% of 1993-2024 based climo that today’s new Euro has for Sept+.

For those wanting a relatively quiet season (including me), the new Euro seasonal NATL forecast is not what you want to see. It has substantially increased from the near normal of last month’s forecast, which had ~125 ACE, to today’s ~155. This is estimated by taking its 130% of normal for Sept+ and adding the 1.5 prior to Aug and its latest Weeklies forecast for Aug, which is now at ~40, well AN. The implied total seasonal # of NS has risen from 15 to ~17-18. The # of H has risen from 6 to ~7.5. The concentration of tracks at/near the Conus has risen from very slightly BN to AN.

Check out the recent trend of the reduced difference in RONI and ONI: RONI-ONI: MJJ 2024 -0.60 JJA -0.54 JAS -0.52 ASO -0.54 SON -0.55 OND -0.55 NDJ -0.55 DJF -0.53 JFM 2025 -0.51 FMA -0.49 MAM -0.43 AMJ -0.38 MJJ -0.32