GaWx

There is a pretty tight spin that appears to be just SE of 32N, 78W. Is that at the surface? Is it tropical? Recon will tell us more. Could go straight to STS or TS.

There’s still plenty of time to drop a good amount per the latest models. CDAS 3.4, TAO buoys, and OHC have all been dropping to their coolest yet. OISST 3.4 has been lagging but I’m looking for it to resume cooling. SOI has been averaging positive overall although it has been negative the last few days. I’m central based weak Niña (ONI based) and moderate Niña (RONI based) based on latest model runs.

The model consensus is suggesting that after the current NE Rex block breaks down and Invest 95L goes inland that there could be a similar 2nd one during the 6-10 blocking things up again. Thereafter, the ensembles suggest a TC moving NE from the W Caribbean (which could be very strong) across or just E of FL is quite possible as the pattern changes to more autumn-like. It wouldn’t be a shocker if that would be the next MH based on its modeled origins. Increased activity then would be consistent with the Euro Weeklies. Based on the Weeklies, more activity originating from the W Caribbean or Gulf would be quite possible the week after that.

0Z: all major global models hit NC except GFS, which hits way down at Georgetown, SC. But that run is 200 miles SW of yesterday’s 0Z and is the most SW of any run since 9/10 12Z. So, it’s likely too far SW. The strongest is the 1002 of the ICON, which along with the CMC, take a pretty direct track to NC. OTOH, the Euro, UKMET, and JMA first go W through Sun night before turning NNE to NC. Tropical Weather Outlook NWS National Hurricane Center Miami FL 200 AM EDT Sun Sep 15 2024 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: Active Systems: The National Hurricane Center is issuing advisories on Tropical Storm Gordon, located over the central tropical Atlantic Ocean. 1. Offshore the Southeastern U.S. Coast: A non-tropical low pressure area has formed along a frontal boundary a couple of hundred miles off the southeastern U.S. coast and is producing winds to gale force north of its center. The low is forecast to move northwestward or northward over the warm waters of the Gulf Stream toward the coasts of North Carolina and South Carolina, and it could become a subtropical or tropical storm during the next day or two if the associated front dissipates and showers and thunderstorms become sufficiently organized. Regardless of tropical or subtropical development, the low is likely to bring gusty winds, heavy rains with the potential for flash flooding, coastal flooding, and dangerous beach conditions to portions of the U.S. Southeast and Mid-Atlantic coast during the next couple of days, and interests in these areas should monitor the system's progress. Additional information can be found in products issued by your local National Weather Service Forecast Office and High Seas Forecasts issued by the National Weather Service. * Formation chance through 48 hours...medium...50 percent. * Formation chance through 7 days...medium...50 percent.

I don’t see a clearcut correlation of NAO with Atlantic tropical activity. Look no further than 2018, way more +NAO than 2024 and the most +NAO hurricane season on record. Yet, it had Michael, Florence, and a total of 8H/15NS. 1979 had David and Frederic. Aug/Sep of 2005 were both +NAO. The most +NAO Sep on record (over +2!), 1989, had Hugo. 1995 was dominated by a +NAO. Sep of 2020 had a +NAO and 10 NS, etc. No correlation of +NAO with less activity looking at the hard data. In addition, the US has already had 3 H hits, more than the avg for the entire season!

The LLC is just NE of 31N, 76W, where SST is ~83F:

This is now Invest 95L.

The extratropical LLC is near 31.5N, 76.5W. Below is the latest SST map (couldn’t save as high res). The LLC is over 84F water in the Gulf Stream. On the progged path, it will cross water as warm as 85. But then they fall sharply to 77-8 at the coast of the Carolinas thanks to recent BN temps/clouds. I’d think that would help keep the storm from being too strong at landfall should it become tropical:

Thanks. It will be interesting to see if during 2028-31 we see the -NAO/near solar min pattern continuing. The last 4 mins back to the mid 1980s have had 1-2 -NAO winters as per that graph and that’s it. Only 1 in 7 of the last 45. So, if the next one waits til then it wouldn’t surprise me. Or will the pattern finally break and one slip in before the late 2020s? Will be fun to follow.

OHC back down to <-1, near Apr low:

Big disconnect over last 2 weeks between OISST (steady) and CDAS/TAO (sig cooling):

Since 1979-80, there have been only 6 winters that had a -0.25- NAO: 1984-5: SS 20 1986-7: SS 6 1995-6: SS 12 2009-10: SS 21 2010-1: SS 33 2020-1: SS 14 So, since 1979-80: 1. NAO winters dropped way down in frequency with only 6 (13%) of 45 following the 25 winters 1954-5 through 1978-9, which had 16 (64%). So, 1979-80 through 2023-4 winters had 1/5 the freq of -NAO winters the prior 25 had 2. All -NAO winters of the last 45 had SS 33 or lower. They averaged 18. 1900+ avg SS: 85. So, the 6 had SS that averaged only 1/5 of the 1900+ avg for all months. 3. Related, the 6 were all within about 2 yrs of min. 4. This graph shows the correlation well:

Latest (early Sep) ONI runs vs early Aug UK steady as usual: ~-0.95 JMA dropped from -0.56 to ~-0.9 French dropped from -0.2 to ~-0.65 BoM: dropped from -0.23 to ~-.5 CFS: rose from -1.39 to ~-1.2 Euro: dropped from -0.29 to ~-0.7 Last year’s Sep: the UK had been steady then too and was perfect with JMA barely too warm and CFS a bit too cool. Euro was moderately too warm and BoM/French were way too warm. Taking all of the above into account, my latest ONI forecast low point is -0.9 to -1.0 and RONI -1.3 to -1.5.

Highest ACE After 9/12 for 1951+: implies ceiling of ~124 1998: 124 (57 prior) 2020: 118 (62 prior) 2005: 110 (135 prior) 2017: 96 (129 prior) 1961: 95 (94 prior) 2016: 94 (46 prior) 1999: 87 (89 prior) 2010: 81 (84 prior) 1963: 80 (32 prior) 2004: 78 (149 prior) As of Sep 12th, 2024 has had ACE of 60. Prior to 2024 the last two La Niña seasons immediately following a super strong El Niño were 2016 and 1998. Note that although they both ended up with well above average ACE, neither was above average as of Sep 12th: - 1998 had 57 as of Sep 12th, very similar to 2024. It had the largest post Sep 12th since 1951 with 124 to give it a season total way up at 181. However, Georges became a H on Sep 17 and a MH on Sep 19. So, it’s soon going to be very hard to keep up with 1998. - 2016 had only 46 as of Sep 12th, well under 2024’s 60. But due to a very active post Sep 12th of 94, it ended the season with 140. It was able to do this even though the next H wasn’t until Sep 29th. So, matching 2016 seems doable if the Euro Weeklies for late Sep-early Oct are onto something and considering 2024 was 14 higher on Sep 12th. So, it seems to me that 2024 ending up with ACE near 150 is still quite possible:

This was a Euro Weeklies post I made on Aug 27: “Today’s Euro Weeklies could be nicknamed “A Tale of Two Seasons”: - Weeks 1-3 (9/2-22): remain only at ~50% of climo overall. These haven’t changed much for days other than a gradual decline. - Week 4 (9/23-29/new week “on the block”): the first forecast for that week is for 120% of climo and it follows the prior week’s modest 70%. So, it’s seeing some kind of sudden change. If it were a reversion to climo, it would be only at 100%, not 120%. Also, this is the first time there has been any week at 120%+ since the 8/16 run.” And on Sep 3 I posted this when 9/30-10/6 first appeared on the Weeklies: that week was quite active on this even back then.

Despite the level of geomagnetic activity noted in that tweet, the daily sunspot #s have actually dropped notably in recent days: if today’s # were to end up at 140 or lower it would be the lowest daily since way back on July 8th. Also, the running 5 day average of <150 is easily the lowest since early July. Aug averaged way up at 215, the highest Aug since 1991. Will this continue? 2024 09 01 2024.668 182 14.5 27 35 2024 09 02 2024.671 195 21.1 25 32 2024 09 03 2024.673 180 21.2 20 23 2024 09 04 2024.676 174 26.1 21 26 2024 09 05 2024.679 181 13.1 15 20 2024 09 06 2024.682 189 13.3 19 24 2024 09 07 2024.684 168 17.9 23 27 2024 09 08 2024.687 171 18.7 20 25 2024 09 09 2024.690 156 19.9 21 24 2024 09 10 2024.693 148 12.9 23 29 2024 09 11 2024.695 152 15.3 27 32 2024 09 12 2024.698 146 11.6 18 22 2024 09 13 2024.701 120 10.5 17 21 https://www.sidc.be/SILSO/DATA/EISN/EISN_current.txt

I’ll self impose a 3 ppd ITT limit on myself for the entire month of Dec if 2024 were to not end Nov with season to date ACE 50+ higher than 2014’s total ACE of 67. So, if 2024 doesn’t reach 117+ ACE by Nov 30, I’ll lose this bet. That’s how confident I am that 2024 is no 2014. ACE is currently at 60, which is right at the 1991-2020 avg for the date. To compare, 2014 was only at 24 then. What’s giving me a lot of confidence are the consistent Euro Weeklies. 9/12/24 Euro Weeklies mean ACE progs (% of climo for the week) (Euro climo based on 2004-23): 9/16-22: 6 (40%)(has been BN) 9/23-29: 14 (110%)(has been NN) 9/30-10/6: 16 (170%)(has been AN)(16 is climo of peak week of 9/9-15) 10/7-13: 10 (140%)(has been AN) - So, the week of 9/30-10/6 is forecasted by the current Weeklies to be the busiest in terms of ACE. This run is essentially predicting peak climo ACE 3 weeks late despite 9/30-10/6 climo already being down 40% from its peak! - As the above shows along with prior runs, the Weeklies have been consistent with a BN late Aug through mid Sept, a NN late Sept, and AN 1st 2 weeks of Oct. So, these signals are rather strong. - This is the 4th run in a row having 9/30-10/6 the busiest week. - Including the current week, the Weeklies are forecasting additional ACE of ~47 as of Oct 13. That would get 2024 to ~107. If that were to verify closely, I’d need only ~10 more ACE for the period Oct 14th-Nov 30th. - With La Niña and a still very warm Atlantic, this shouldn’t be difficult to attain.

9/12/24 Euro Weeklies mean ACE progs (% of climo for the week) (Euro climo based on 2004-23): 9/16-22: 6 (40%)(has been BN) 9/23-29: 14 (110%)(has been NN) 9/30-10/6: 16 (170%)(has been AN)(16 is climo of peak week of 9/9-15) 10/7-13: 10 (140%)(has been AN) - So, the week of 9/30-10/6 is forecasted by the current Weeklies to be the busiest in terms of ACE. This run is essentially predicting peak climo ACE 3 weeks late despite 9/30-10/6 climo already being down 40% from its peak! - As the above shows along with prior runs, the Weeklies have been consistent with a BN late Aug through mid Sept, a NN late Sept, and AN 1st 2 weeks of Oct. So, these signals are rather strong. - This is the 4th run in a row having 9/30-10/6 the busiest week. - So, this run is predicting ACE to be ~107 as of Oct 13th. (I added a point for 9/13-5 though there may be none.)

Regarding the potential low forming off the SE: AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 445 PM EDT THU SEP 12 2024 SATURDAY AND SUNDAY: AS MUCH OF THE FORECAST STILL DEPENDS ON WHETHER THIS LOW PRESSURE DEVELOPS OFF OF THE SE COAST, HIGH UNCERTAINTY STILL EXISTS. ALL THE MODELS ARE PLAYING OUT A DIFFERENT SCENARIO AS TO IF AND WHEN THE LOW DEVELOPS, AND HOW STRONG IT IS GOING TO BE. NHC HAS A 30% OF TROPICAL DEVELOPMENT FOR THIS LOW ON THEIR 7-DAY TROPICAL OUTLOOK. TO SAY THE LEAST, THERE IS A LOT TO DETERMINE IN THE NEXT COUPLE OF DAYS. LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/ HIGH UNCERTAINTY EXISTS IN THE LONG TERM PERIOD, ESPECIALLY WITH THE DETAILS OF THE TIMING, PLACEMENT, AND INTENSITY OF A POTENTIAL COASTAL LOW PRESSURE.

These blocking types of patterns are notoriously difficult for the models to get a handle on, which is exhibited by the widely varying 12Z model solutions. This is what JB calls the “ridge over troubled water” pattern.

Regarding the potential TC or STC forming just off the SE coast by early next week, here are some 12Z model runs: -GFS 1003 TS that landfalls near Wilmington, NC -CMC/UKMET/ICON no TC/STC -Euro: a very weak low (1011) that landfalls at GA/SC border -JMA: low moves NE to 350 miles E of NC/VA border at 1003 (ST or T); then stalls and is forced back SW to 300 miles E of Hatteras while strengthening to 998 at 192

0Z UKMET is its 1st run with a (S)TC forming offshore the SE; forms Sun night as TS or STS ~100 miles ESE of lower SC coast, moves WNW, and landfalls lower SC on Tue with CHS on the dirty side: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 108 HOURS FORECAST POSITION AT T+108 : 31.5N 79.1W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 16.09.2024 108 31.5N 79.1W 1008 38 0000UTC 17.09.2024 120 31.4N 79.6W 1007 30 1200UTC 17.09.2024 132 32.1N 80.3W 1009 30 0000UTC 18.09.2024 144 CEASED TRACKING ————————— Edit: So far I’m not seeing any surface low forming off the SE coast on 0Z Euro

12Z JMA has a weak low go into S NC but not til hour 168, which is ~48 hours after GFS/CMC. So very much a fwiw.

That’s now TD #7. Please see posts above addressing it.

The 12Z Euro has only a hardly detectable very weak surface low just offshore SC/GA. So, the Euro and UKMET have nothing significant. The ICON is well offshore with a 1007 sfc low. The GFS/CMC have a TS or STS move back into ~S NC. So, no consensus.