GaWx

Interesting thoughts! And just like that, the 12Z Euro doesn't recurve it. Instead it starts out like it will recurve, but then it turns back W, then WSW, and then SW while weakening. Also, it comes off about 12 hours earlier than the prior run and closer to the timing of the GFS/CMC though still slower than those. These run to run changes and model differences show me that it is still too early to make a definitive call on what this AEW moving off ~9/11 will or won't do. After all, it is still ~6 days away from the coast and a lot can change before then. Old Euro run (0Z) is along the African coast moving back inland to the NE: New Euro run (12) is 400 miles to the WSW about to turn SW and weaken:

Per the 12Z GFS and CMC, that strong AEW over Africa that especially the Euro but also the ICON have been developing on 9/11 just offshore never recurves but instead stays weak and moves WSW in the E Atlantic. You can actually trace the vorticity/precip associated with it on the 12Z GFS then move W all of the way to the Lesser Antilles on 9/17 followed by it moving WNW into the Caribbean but staying very weak.

There’s no suggestion Sept will turn out quiet. First, Larry is looking to end up being a hurricane for 10+ days and a MH for most of that period. In terms of ACE, that’s strong activity by itself….lots of energy for the first 13+ days of the month! Second, if the EPS has the right idea, there will be only a couple of days between the demise of Larry and the next MDR system or two. Third, there’s the threat of Gulf activity over the next 10 days or so. That may produce 1-2 more TCs. Fourth, ensembles go out only through 9/20. That still leaves 1/3 of the month that can’t even be seen yet. Fifth, there usually are one or more TCs that aren’t even hinted at far in advance on models. Sixth, there’s still the very real chance of a far eastern MDR TC, sharp recurve or not, near 9/11-12 from the suggested very strong AEW still forecasted over Africa in a few days and then moving offshore ~9/11. So, there really is no indication of anything less than an active Sept based on objective measurements.

0Z EPS is still very active in the MDR late in the run/something to watch for late Sept: H5:

The signal for genesis of an AEW in mid-Sep along with mainly W movement is still there on the 12Z EPS. However, regarding the strong AEW still progged by several models to come off Africa ~9/11, the trend is for a sharp recurve due to a weakness in the far E Atlantic, which has gotten more prominent on the Euro suites as the high is further west in the mid Atlantic Ocean. So, it appears that there will probably be a strong AEW moving off 9/11 probably followed by a sharp recurve followed by an AEW moving off near 9/14-5 that then likely moves W to WNW well out into the Atlantic. We’ll see though as that’s still 10 days out and much can change just like the changes with the 9/11 wave. Here’s the 12Z EPS still showing a strong signal for a W to WNW moving AEW just after midmonth, which would need to be watched for late month:

12Z EPS at 360: most of these originate from a followup wave to the 9/11 one and almost all of these are moving pretty rapidly due W or just N of due W: 12Z EPS H5 at 360 has strong ridging to the north allowing for pretty rapid movement W or just N of due W: (the danger is not that this one high would move it all of the way to the other side but rather there's usually a mid ocean weakness sometimes followed by a handoff to a strengthening WAR).

Consistent with the prior 3 Euro runs, the 12Z yet again has a TS just off Africa that originates from an AEW that comes off ~9/11. But this time it comes off quite far north (near 20N) and thus easily recurves just offshore:

12Z UKMET: strongest yet (920mb!!) 250 miles E of Bermuda: HURRICANE LARRY ANALYSED POSITION : 14.5N 40.1W ATCF IDENTIFIER : AL122021 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 03.09.2021 0 14.5N 40.1W 982 55 0000UTC 04.09.2021 12 15.5N 42.7W 981 58 1200UTC 04.09.2021 24 16.7N 45.4W 982 55 0000UTC 05.09.2021 36 17.8N 47.6W 980 59 1200UTC 05.09.2021 48 19.4N 49.7W 976 63 0000UTC 06.09.2021 60 21.1N 51.5W 970 67 1200UTC 06.09.2021 72 22.4N 53.5W 960 73 0000UTC 07.09.2021 84 23.6N 55.1W 949 88 1200UTC 07.09.2021 96 25.0N 56.9W 946 94 0000UTC 08.09.2021 108 26.6N 58.3W 928 105 1200UTC 08.09.2021 120 28.8N 59.7W 927 105 0000UTC 09.09.2021 132 31.4N 60.7W 920 110 1200UTC 09.09.2021 144 34.4N 61.1W 922 107

Consistent with the above 12Z Euro and the run before that, the 0Z Euro still has a TS from an AEW coming off Africa on 9/11 with a strong high to its NNW: End of run:

0Z UKMET is again down to 922-3 mb and passes only 150 miles east of Bermuda then: HURRICANE LARRY ANALYSED POSITION : 13.9N 36.8W ATCF IDENTIFIER : AL122021 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 03.09.2021 0 13.9N 36.8W 988 50 1200UTC 03.09.2021 12 14.5N 40.3W 986 49 0000UTC 04.09.2021 24 15.5N 43.1W 983 54 1200UTC 04.09.2021 36 16.6N 45.8W 979 60 0000UTC 05.09.2021 48 18.0N 47.8W 972 64 1200UTC 05.09.2021 60 19.4N 49.9W 971 66 0000UTC 06.09.2021 72 20.8N 52.0W 961 72 1200UTC 06.09.2021 84 22.0N 53.8W 950 84 0000UTC 07.09.2021 96 23.3N 55.5W 936 100 1200UTC 07.09.2021 108 25.2N 57.6W 933 97 0000UTC 08.09.2021 120 27.2N 59.5W 927 103 1200UTC 08.09.2021 132 29.5N 61.4W 922 112 0000UTC 09.09.2021 144 32.5N 62.5W 923 111

12Z EPS continues with a lot of activity in the MDR during the 11-15 day period from various AEWs, which the US may have to monitor for after 9/20:

12Z EPS has many more members vs prior runs hitting or grazing E New England or Canada vs the 0Z:

12Z Euro, like the 0Z Euro, has a TS just off the coast of Africa 9/11. This is consistent with the EPS runs I’ve been posting. Note how strong the central Atlantic high is to the NNW of it. If that were to verify, this likely wouldn’t recurve early and may even soon after this start moving WSW for a period, which would be a warning signal as Yaakov ( @jconsor) and I have noted, especially with the La Nina(ish) ENSO:

12Z UKMET: down to 922 mb at the end! But again, very low US threat. Bermuda needs to watch closely. HURRICANE LARRY ANALYSED POSITION : 13.3N 33.3W ATCF IDENTIFIER : AL122021 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 02.09.2021 0 13.3N 33.3W 993 48 0000UTC 03.09.2021 12 13.8N 37.2W 988 50 1200UTC 03.09.2021 24 14.4N 40.5W 983 52 0000UTC 04.09.2021 36 15.3N 43.6W 977 62 1200UTC 04.09.2021 48 16.3N 46.2W 975 65 0000UTC 05.09.2021 60 17.6N 48.3W 971 65 1200UTC 05.09.2021 72 19.2N 50.6W 969 68 0000UTC 06.09.2021 84 20.9N 52.5W 960 77 1200UTC 06.09.2021 96 22.2N 54.4W 949 81 0000UTC 07.09.2021 108 23.6N 56.1W 941 97 1200UTC 07.09.2021 120 25.0N 57.8W 930 106 0000UTC 08.09.2021 132 27.3N 59.1W 922 107 1200UTC 08.09.2021 144 29.9N 60.0W 922 111

Larry has not moved S of due W between any two reference points. It moved due west between 8 AM and 2 PM yesterday and otherwise N of due W to WNW.

Still watching this timeframe as the 0Z EPS still has something coming off Africa ~9/11: End of the run:

0Z UKMET: down to 927 mb at the end pf the run! TROPICAL STORM LARRY ANALYSED POSITION : 12.5N 29.8W ATCF IDENTIFIER : AL122021 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 02.09.2021 0 12.5N 29.8W 1002 41 1200UTC 02.09.2021 12 13.0N 34.0W 996 45 0000UTC 03.09.2021 24 13.6N 37.5W 993 44 1200UTC 03.09.2021 36 14.2N 41.0W 989 49 0000UTC 04.09.2021 48 15.3N 44.1W 981 54 1200UTC 04.09.2021 60 16.7N 47.0W 974 65 0000UTC 05.09.2021 72 18.1N 49.5W 971 62 1200UTC 05.09.2021 84 19.8N 51.8W 972 64 0000UTC 06.09.2021 96 21.4N 53.5W 969 67 1200UTC 06.09.2021 108 22.8N 55.1W 965 64 0000UTC 07.09.2021 120 24.0N 56.5W 952 81 1200UTC 07.09.2021 132 25.3N 57.9W 939 101 0000UTC 08.09.2021 144 26.8N 58.5W 927 105

Great stuff. Actually, I happened to have studied eastern Atlantic WSW movers, myself, a while back and saved this list of the 12 that made US landfall (all but Carol of 1953 hit as a hurricane)(# in parentheses is days from African coast to US landfall): - #6 of 1893 (GA/SC) (14) - #4 of 1928 (FL)(11) - #4 of 1947 (FL, LA) (14) - Able of 1952 (SC) (13) - Carol of 1953 (ME grazed) (11) - Donna of 1960 (FL, NC, New England) (12) - Dora of 1964 (FL) (13) - Allen of 1980 (TX) (12) - Hugo of 1989 (SC) (12) - Fran of 1996 (NC) (14) - Isabel of 2003 (NC) (15) - Ivan of 2004 (AL/FL) (16)

Following up from yesterday: today's 12Z EPS has similar activity and may be the next AEW to watch closely in the CONUS for after 9/20:

I'm still not concerned about Larry to be, but am somewhat more interested in what may happen a bit afterward. Way out in cartoonland, the 12Z EPS has an AEW that moves off Africa ~9/11 with many members remaining pretty weak but more importantly moving briskly westward. This may be a sign that it would move much further west than Larry. With it being La Nina or close to it, the climo of AEW's like this one says they have a better chance to get into the western basin than for other ENSO. That climo also says that AEWs that come off Africa through mid Sept., especially during La Nina, still often get pretty far west. Even so, it wouldn't be til 9/21+ that it could reach the CONUS based on this 9/15 map:

Wow, the 3.4 Nino weekly anomaly released today for last week warmed a whopping 0.6 C from -0.9 to -0.3! Whereas I’m sticking with my moderate La Niña call, that much warming was quite the surprise for me and doesn’t exactly help my confidence. We’ll see what the next few weeks bring. Looking at records, an anomaly warming of 0.6+ in one week is rare though oddly enough 4 of the 5 occurrences over the last 31 years happened within just the last 2 years: 8/25/21 warmed 0.6 6/24/20 warmed 0.6 9/25/19 warmed 0.7 11/21/18 warmed 0.6 7/8/92 warmed 0.6 That's it for warmings of 0.6+ back to 1990!

N.O. and vicinity now has over 90% of customers without power:

Going rapidly downhill at N.O. (Ignore the 32 dewpoints). Intl Airport dropped 5 mb in the last hour and has 1/4 mile vis. There now is a whopping ~9 mb difference between there and Lakefront! N.O. INTL ARPT HVY RAIN 77 32 19 E56G83 29.01F VSB 1/4 N.O. DWNTWN HE RAIN 78 76 93 MISG N/A VSB 1 N.O. LAKEFRONT HVY RAIN 77 32 19 E46G71 29.27F VSB 1/2

Latest LA outage map shows ~2/3 of N.O. area out of power: