GaWx

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.

I am not trying to be argumentative in my response here, but I am lost on any correlation, much less causation with respect to sunspot activity and solar influences as inhibiting factors for cyclogenesis. During the same long-duration interseasonal quiet stretch in the Atlantic basin, we saw active stretches in the western and eastern Pacific basins. Solar influences should not discriminate between bodies of water. We have plenty of evidence of phenomenon contained within the troposphere to hypothesize why the Atlantic has struggled versus the WPAC and EPAC. Greater stability across the MDR due to +2-3°C warmer tropopause is among the evidence. But attributing that to sunspot activity seems more of a stretch than SPH placement, MJO, and meridional SSTs negative feedback to counter atmospheric lift versus subsidence. There has been speculation about numerous possibilities. Pro mets as a whole weren’t able to predict the quiet despite the possible factors that you mentioned. Why not? Pro mets are in disagreement as they don’t know. It’s probably from a combo of factors. A very active sun is one possible contributor and a partial negative correlation between solar activity and atmospheric stability (via more heating of upper trop/lower strat) has been hypothesized. Many papers addressing the possible connection have been written since 2008, including those in my post below. Joe D’Aleo was who first brought it to my attention just a couple of weeks ago, but that wasn’t enough as I wanted to see papers. Now I’ve seen them. Thus, I’m now open-minded about this possibility. This graph was put together by Teban at Storm2K. It suggests to me that a ceiling on ACE does seem to be the highest when sunspot number is relatively low.

Yeah, I was wondering about that but dewpoints on 12Z GFS are uniformly warm all around the surface low center. So, GFS looks tropical.

More 12Z: GFS/CMC have a TS form offshore the SE that moves back into S NC to SC/NC border, similar to 0Z Euro, but far different from ICON UKMET has no TC identified in its textual output

The ICON (arguably as good of a global model as any recently) on the new run (12Z) continues to be far different from the model consensus that has a surface low form just off the SE US this weekend into early next week. The ICON continues to develop it well offshore the E US.

Daily sunspot levels Sept MTD: general downward trend has continued. Perhaps the increased activity in the basin is partially related. Keeping an open mind because nobody knows. 2024 09 01 2024.668 182 14.5 27 35 2024 09 02 2024.671 195 21.1 25 32 2024 09 03 2024.673 179 22.2 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 2024.684 167 17.0 22 26 2024 09 08 2024.687 173 17.5 19 24 2024 09 09 2024.690 156 19.9 21 24 2024 09 10 2024.693 149 11.4 20 26 2024 09 11 2024.695 152 15.7 20 23 @Seminole

Not a land threat but a potentially significant ACE producer: Eastern and Central Tropical Atlantic (AL93):Updated: Recent satellite-wind data indicates that the system located a few hundred miles to the west-southwest of the Cabo Verde Islands has developed a well-defined circulation. In addition, showers and thunderstorms continue to show signs of organization, and if these trends continue, advisories will be issued on a tropical depression later this morning. The system is moving to the west-northwest at 10 to 15 mph and will be moving into the central Tropical Atlantic by the end of the week.* Formation chance through 48 hours...high...90 percent.* Formation chance through 7 days...high...90 percent.

From CHS NWS: LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/ HIGH PRESSURE WILL CONTINUE TO EXTEND SOUTH INTO THE REGION EARLY NEXT WEEK. MODELS INDICATE THAT AN AREA OF LOW PRESSURE COULD BE LOCATED WELL OFFSHORE ALONG A STALLED FRONT. THE EVOLUTION OF THIS FEATURE IS STILL UNCERTAIN, SO THERE IS LOWER CONFIDENCE IN THE FORECAST AT THIS JUNCTURE, BUT THE LOW COULD TAKE A TRACK BACK TOWARDS THE SOUTHEAST COAST LATER IN THE PERIOD. MAINTAINED CHANCE POPS EACH DAY, GENERALLY IN THE 30-40% RANGE.

12Z UKMET: landfall now into SE LA, a bit further E vs 0Z; then goes N through E MS and dissipates near KY TROPICAL STORM FRANCINE ANALYSED POSITION : 24.4N 95.8W ATCF IDENTIFIER : AL062024 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 10.09.2024 0 24.4N 95.8W 996 37 0000UTC 11.09.2024 12 25.9N 94.5W 994 36 1200UTC 11.09.2024 24 27.6N 93.1W 992 44 0000UTC 12.09.2024 36 29.2N 90.5W 989 40 1200UTC 12.09.2024 48 31.4N 89.3W 991 34 0000UTC 13.09.2024 60 34.3N 88.3W 994 24 1200UTC 13.09.2024 72 36.5N 89.1W 999 16 0000UTC 14.09.2024 84 36.6N 88.5W 1005 15 1200UTC 14.09.2024 96 37.7N 87.6W 1009 19 0000UTC 15.09.2024 108 CEASED TRACKING

Can anyone explain why the difference between the cold biased CDAS and the OISST is relatively large currently? It is near the largest of the last few months it appears (0.45): CDAS OISST:

0Z UKMET: similar LA landfall location/strength followed by NNE move to E MS; then N move to far W KY followed by dissipation near IL/IN border TROPICAL STORM FRANCINE ANALYSED POSITION : 24.1N 96.3W ATCF IDENTIFIER : AL062024 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 10.09.2024 0 24.1N 96.3W 1002 41 1200UTC 10.09.2024 12 24.7N 95.4W 999 35 0000UTC 11.09.2024 24 26.3N 94.2W 995 33 1200UTC 11.09.2024 36 28.4N 92.6W 991 49 0000UTC 12.09.2024 48 30.2N 90.4W 991 37 1200UTC 12.09.2024 60 32.7N 89.5W 995 26 0000UTC 13.09.2024 72 35.3N 89.1W 997 21 1200UTC 13.09.2024 84 36.5N 89.1W 1001 15 0000UTC 14.09.2024 96 37.7N 87.9W 1007 17 1200UTC 14.09.2024 108 38.9N 88.5W 1011 17 0000UTC 15.09.2024 120 CEASED TRACKING

18Z Euro: quite a bit faster as it landfalls at 4PM CDT on Wednesday vs the 12Z’s 11 PM CDT; strength at landfall the same though at 977 mb; keep in mind though that initialization is up at 1003 mb