GaWx

0Z UKMET: becomes a TC 36 hours earlier vs 12Z run; back on the coast NC to NJ NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 24 HOURS FORECAST POSITION AT T+ 24 : 30.4N 74.8W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 22.09.2023 24 30.4N 74.8W 1007 38 1200UTC 22.09.2023 36 32.4N 75.0W 1004 44 0000UTC 23.09.2023 48 33.4N 75.9W 997 45 1200UTC 23.09.2023 60 35.4N 76.0W 995 43 0000UTC 24.09.2023 72 37.8N 75.7W 994 40 1200UTC 24.09.2023 84 39.1N 74.6W 1001 32 0000UTC 25.09.2023 96 39.9N 73.5W 1007 33 1200UTC 25.09.2023 108 40.0N 72.2W 1009 34 0000UTC 26.09.2023 120 39.5N 69.6W 1011 34 1200UTC 26.09.2023 132 CEASED TRACKING

Is JB copying my posts? I beat him to the punch by 4 hours : I think that another home brew under the next big NE high late next week is much more likely than the 18Z GFS idea of that storm coming all the way to the CONUS. There’s no room for both and the 18Z GFS is an extreme outlier considering its own ensemble, other models, and climo (lateness for that kind of track). A home brew under a big and strong high OTOH wouldn’t be. Of course neither may happen.

Fwiw, 12Z Euro says “Ridge Over Troubled Water” part two late next week with a second big (actually stronger) NE US surface high: https://www.tropicaltidbits.com/analysis/models/?model=ec-fast&region=us&pkg=z500_mslp&runtime=2023092012&fh=216

Thanks. Why wouldn’t Pinatubo add to instead of subtract from the value of 1994-5 as an analog?

Thanks. 1. Why don’t you think Pinatubo adds to the strength of 1994-5 as an analog? 2. Since you and I agree on the idea of attempts to overly attribute wx to AGW even though we both fully accept AGW as real, I thought you might find this reply that I just made interesting regarding an article citing an attempt to partially attribute increased Midwest rainfall in recent decades to AGW:

From this article: But that doesn’t mean global warming has somehow skipped the central US: In a weird twist, climate change may be partly responsible for this gap. Interestingly enough, the conditions that contribute to the hole actually begin thousands of miles to the west, in the tropical Pacific. “Changing ocean surface temperatures, partly caused by global warming and partly caused by naturally occurring variability, are producing the downstream changes in atmospheric circulation over the US,” says Gerald Meehl, a senior scientist at the National Center for Atmospheric Research, who wasn’t involved in the new research. “This paper confirms earlier work that these changes in circulation are bringing this cooler and wetter weather into parts of the eastern US.” This seems like a reach to try to attribute the wetter wx in the Midwest to AGW. This is a very weak argument at best imo. I favor calling it a combo of mainly much higher crop production (which has likely been helped by increased CO2) along with natural variability. Besides, an increase in droughts is supposed to occur due to AGW. I’m not doubting AGW at all (very much unlike Joe Bastardi for example, who’s ignoring scientifically supported facts/evidence). But I do question some of the attempts to attribute too many things to AGW without solid evidence. Overdoing attribution only serves imo to make it more difficult to educate folks about the reality of AGW because I feel it creates straw-men.

What about 1994-5 as a potentially good RONI/PDO/PNA analog? RONI peak (NDJ) was +1.42 while DJF PDO was -1.02. DJF PNA was solidly positive. DJF was central to west based (definitely not east based).

The 12Z UKMET dropped this from becoming a TC. UK goes through 168.

Here was the 0Z UKMET (12Z is further down in this post): NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 66 HOURS FORECAST POSITION AT T+ 66 : 32.2N 76.5W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 23.09.2023 72 34.2N 75.6W 1004 43 1200UTC 23.09.2023 84 36.3N 75.0W 1001 48 0000UTC 24.09.2023 96 39.1N 73.1W 998 42 1200UTC 24.09.2023 108 42.1N 69.4W 998 39 0000UTC 25.09.2023 120 45.5N 64.0W 995 41 1200UTC 25.09.2023 132 46.8N 63.5W 993 45 0000UTC 26.09.2023 144 46.3N 60.6W 999 41 1200UTC 26.09.2023 156 45.9N 55.9W 1005 29 0000UTC 27.09.2023 168 CEASED TRACKING 12Z UKMET is back to being more offshore with a TC: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 72 HOURS FORECAST POSITION AT T+ 72 : 35.5N 74.1W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 23.09.2023 72 35.5N 74.1W 1006 42 0000UTC 24.09.2023 84 37.7N 72.3W 1003 38 1200UTC 24.09.2023 96 40.9N 67.9W 1004 34 0000UTC 25.09.2023 108 43.6N 62.1W 1004 36 1200UTC 25.09.2023 120 43.9N 58.3W 1004 39 0000UTC 26.09.2023 132 CEASED TRACKING

When considering the progged RONI along with assuming a solid -PDO this winter, 1994-5 could easily be the closest analog. The RONI peak was +1.42 (NDJ), which we could end up close to. The DJF PDO was down at -1.02, a strong -PDO. RONI: https://www.cpc.ncep.noaa.gov/data/indices/RONI.ascii.txt PDO: https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat But how likely is it that the DJF PDO will be strongly negative though? Does anyone have a good feel for the upcoming DJF PDO? The 30+ moderate+ El Niño events outside of 1994-5 going all of the way back to the 1850s says to look to not have a strongly -PDO.

I’ve found only three storms on record since the late 1800s that have formed in the MDR E of 50W Sep 20+ and hit the CONUS: 1) 2002’s Lili: TD formed 9/21 near 45W and hit LA 10/3 as a H; El Nino 2) 1966’s Inez: TD formed 9/21 near 35W and hit FL Keys 10/4 as a H; not El Niño 3) 1893’s storm #9 formed 9/25 near 25W and hit Carolinas 10/13 as a MH; not El Nino

12Z UKMET had this (0Z is further down in this post): NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 54 HOURS FORECAST POSITION AT T+ 54 : 14.5N 27.2W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 22.09.2023 60 14.5N 29.0W 1008 31 1200UTC 22.09.2023 72 15.0N 32.2W 1007 32 0000UTC 23.09.2023 84 15.3N 34.9W 1006 36 1200UTC 23.09.2023 96 15.8N 37.9W 1005 38 0000UTC 24.09.2023 108 16.3N 39.9W 1005 37 1200UTC 24.09.2023 120 16.7N 42.4W 1004 44 0000UTC 25.09.2023 132 17.4N 44.3W 1003 47 1200UTC 25.09.2023 144 17.3N 46.7W 1003 48 0000UTC 26.09.2023 156 17.2N 48.9W 1003 47 1200UTC 26.09.2023 168 17.1N 49.9W 1001 60 ——————— 0Z UKMET: At 168 hours TS moving W at 15 mph 300 mi NE of Leewards NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 60 HOURS FORECAST POSITION AT T+ 60 : 15.0N 33.7W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 22.09.2023 60 15.0N 33.7W 1009 30 0000UTC 23.09.2023 72 15.6N 36.3W 1008 30 1200UTC 23.09.2023 84 16.0N 39.3W 1008 31 0000UTC 24.09.2023 96 16.3N 41.7W 1008 30 1200UTC 24.09.2023 108 16.4N 43.6W 1007 37 0000UTC 25.09.2023 120 17.2N 46.4W 1007 36 1200UTC 25.09.2023 132 17.8N 49.2W 1008 37 0000UTC 26.09.2023 144 18.3N 52.1W 1008 42 1200UTC 26.09.2023 156 18.6N 55.5W 1007 42 0000UTC 27.09.2023 168 18.4N 58.2W 1005 37

More on these amateur forecasts with most warm, dry in the NW and cold, snowy E coast: Weather Watcher: what a winter along E coast! Weather William: winter will be rockin’ in the east! Direct Wx: get your shovels ready in the east! America Climate Channel: amazing winter for the east! NWW116 goes big in the east! AWF: Lives in GA and has their coldest and one of snowiest winters of last 45 yrs 2009-10 as top analog! Weather At A (15 minute long) Glance: David S for NE: probably one of worst winters; “big, deep trouble, almost historic, winter-mageddon”! MBGC says wild winter coming, especially NE; 2009-10 favorite analog! Direct Wx’s favorite video of year: official snowfall forecast with snow to Savannah!!

Yes, in locations away from where the forecaster lives. That’s the key. Not necessarily exactly as you stated, but a “benign” winter. For example, literally every amateur forecast I’ve seen so far for this winter from those not living in the W, which includes just about every forecast I’ve seen, has the W mild/benign and the E cold along with AN snow. They’re all almost carbon copies of each other’s forecast. Their forecasts are much more predictable than what they’re trying to predict. This is influenced a lot by weenieism as well as the desire to get more clicks. Their bias dominates. I should emphasize that I’m talking about the amateur forecasters that I’ve seen so far. I’m not at all talking about objective amateur and pro forecasters without a hidden agenda who put the desire for accuracy ahead of weenieism and getting clicks.

The BOM and CFS have both been overdoing the MJO, especially in and near phase 5, since at least spring. The CFS has recently been forecasting a phase 5 in early OCT but is now staying inside the COD.

Yeah it only skirts the NC OB. But even so, a few areas in E NC get up to 4-8” of rainfall on the Euro: https://www.pivotalweather.com/model.php?m=ecmwf_full&p=qpf_120h-met&rh=2023091912&fh=132&r=nwatl&dpdt=&mc=

The 12Z Euro op at hour 90 near 100 miles E of N FL is on the SW side of the EPS member envelope as the EPS mean is 100 miles NE of there: https://www.pivotalweather.com/model.php?m=epsens&p=sfcmslp-meanmem&rh=2023091912&fh=90&r=us_se&dpdt=&mc=

Looks pretty close to a STS at hour 90 of the 12Z Euro centered off N FL. Note the 35 knot wind barbs off N FL/GA/SC and the good organization and low SLP of 1002 mb: https://www.pivotalweather.com/model.php?m=ecmwf_full&p=sfcwind_mslp&rh=2023091912&fh=90&r=swatl&dpdt=&mc=

Looks pretty close to a STS at hour 90 of the 12Z Euro centered off N FL. Note the 35 knot wind barbs off N FL/GA/SC and the good organization and low SLP of 1002 mb: https://www.pivotalweather.com/model.php?m=ecmwf_full&p=sfcwind_mslp&rh=2023091912&fh=90&r=swatl&dpdt=&mc=

The SOI is at 31 days in a row of negative dailies, the longest streak so far this year. The 30 day average is back down to ~-15, indicative of solid El Niño atmospheric conditions. In general, Nino 3.4 has tended to warm during the several weeks following long solid -SOI periods like this although there’s lots of variation. The OISST SSTa daily graph shows new highs in both 3.4 and 4 today with 3.4 near +1.7. I expect warming to dominate for the next few weeks meaning a decent shot at 3.4 reaching +2.0 on the OISST dailies in early Oct: https://www.longpaddock.qld.gov.au/soi/ ##Corrected to say new highs in 3.4 and 4

After the 0Z run not turning this into a TC and the prior 12Z having it become a TC but staying offshore, this new 12Z UKMET is back to having a TC, is a bit stronger, and it moves N to a landfall near the NC OB Saturday 9/23 followed by a crawl up the coast to DelMarVa pen/dissipation on Mon 9/25. This very slow movement and track is likely bringing very heavy rains to the mid-Atlantic coastal area: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 78 HOURS FORECAST POSITION AT T+ 78 : 32.5N 77.0W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 23.09.2023 84 32.7N 76.4W 1006 47 1200UTC 23.09.2023 96 35.4N 76.1W 1003 42 0000UTC 24.09.2023 108 37.3N 76.3W 1001 40 1200UTC 24.09.2023 120 37.9N 76.2W 1007 33 0000UTC 25.09.2023 132 37.7N 76.1W 1012 32 1200UTC 25.09.2023 144 38.2N 75.7W 1015 32 0000UTC 26.09.2023 156 CEASED TRACKING

Has anyone seen this map of the correlation between DJF ONI and DJF snowfall? I’ve studied Atlanta extensively and I can vouch for the ~+0.25 there. What about other locations?

The late August peak was ~Aug 25th, which coincides with the first image in this OHC animation (average of 5 days ending Aug 27th). From then to just about all of the way to the end, this animation mainly shows slow cooling and still doesn’t show any signs of another round of significant OHC rewarming being imminent at the end. In contrast the loops ending in early August clearly showed strong rewarming about to commence, which of course happened. There’s still time (~remainder of autumn) but I’m admittedly saying to myself “hmmm” because I didn’t expect a 3 week long slow cooling/pause of OHC along with still no sign of it ending. And now BoA finally cooled significantly for its 3.4 peak and thus joined the cooling vs one month ago runs party although @snowman19correctly pointed out that its initialization was too cool.

The SSTa image below from Sep 13th shows that significant cooling of the upper ocean resulting from slow moving large and major H Lee stirring up the waters started well before center passage. Note that at 11AM EDT on Sep 13th Lee was still down at 26.4N, 67.2W, despite a new blue area that stretches as far NW as 29N, 69W, that was yellow the prior day. So, the SST had already cooled ~1F all the way up at 29N, 69W, vs 24 hours earlier even though the center was still over 200 miles to the SE at the end of that 24 hours. The center didn’t even get near 29N, 69W, for another ~18 hours, during which that area and nearby cooled more. During the analyzed period, Lee was moving under 10 mph and getting larger. I was educatedly guessing that Lee’s slow movement combined with large size was helping to keep its strength in check by causing SST cooling well ahead of the center. I assume that a little cooling well ahead of a center would be normal but this appears to have been more than average cooling due to a combo of slow movement and large size:

Coolest/lowest dewpoints of any day in months! Hope to walk outside!