GaWx

Regarding this nor’easter, here’s chaser Josh-iCyclone’s take:

For the E MDR lemon from the 2PM TWO: 2. Eastern Tropical Atlantic: A tropical wave just offshore of the west coast of Africa is producing an area of disorganized showers and thunderstorms. Some slow development of this system is possible towards the latter part of this week as it moves westward at 15 to 20 mph, moving from the eastern to central portion of the tropical Atlantic. * Formation chance through 48 hours...low...near 0 percent. * Formation chance through 7 days...low...20 percent.

More 12Z runs: The models have switched in some cases. The GFS/CMC moved W to just SE of Bermuda whereas the Euro moved E to well E of Bermuda. Icon: still well to the SW of others with it much weaker SSW of Bermuda then recurving NWJMA: TS at Bermuda at 192

Great Q, big ten fan! 1. The UK has been found to be a top tier model when looking at average errors over the longterm. 2. I like to post all of the majors, good model or not. But I like to post the UK also for some other reasons like: -it’s the only one I can find with definitive textual output that’s easy to post without taking up image space and it allows one to post the entire run for a TC on just one page -so, it’s also good for documentation purposes for when one wants to look back at it for a particular TC or a TC that never formed like the recent Invest 91L -this complete run’s textual output comes out earlier than all but the Icon of the majors -The UKMET is often overlooked. You see lots of Icon, GFS, and Euro posts, but hardly any UK despite it overall being a good model. So, I happily fill in that gap.

12Z UKMET: center passes just SE of Bermuda NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 36 HOURS FORECAST POSITION AT T+ 36 : 19.4N 49.2W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 18.09.2025 36 19.4N 49.2W 1008 42 1200UTC 18.09.2025 48 20.2N 51.3W 1007 37 0000UTC 19.09.2025 60 21.1N 53.9W 1007 33 1200UTC 19.09.2025 72 21.6N 56.5W 1008 28 0000UTC 20.09.2025 84 22.8N 58.1W 1008 31 1200UTC 20.09.2025 96 24.1N 59.6W 1009 30 0000UTC 21.09.2025 108 25.8N 59.8W 1008 37 1200UTC 21.09.2025 120 27.3N 61.2W 1005 46 0000UTC 22.09.2025 132 28.8N 62.3W 1003 44 1200UTC 22.09.2025 144 30.3N 63.0W 1001 44 0000UTC 23.09.2025 156 31.7N 63.0W 1000 49 1200UTC 23.09.2025 168 32.5N 61.5W 998 43

Good discussions all! Unlike like the last couple of runs, the 12Z UKMET has no followup TC to 92L.

Maybe we need a RAMO (relative AMO) in addition to classic AMO sort of like we now have RONI in addition to the classic ONI.

Do you think that this possibly could have properly been classified as a subtropical storm? Is this mainly a baroclinic low but with some tropical characteristics?

2. Eastern Tropical Atlantic: A tropical wave emerging off the west coast of Africa is producing an area of disorganized showers and thunderstorms. Some slow development of this system is possible towards the mid to latter part of this week as it moves westward at 15 to 20 mph, moving from the eastern to central portion of the tropical Atlantic. * Formation chance through 48 hours...low...near 0 percent. * Formation chance through 7 days...low...20 percent.

But what do you think about the possibility that this also has some tropical characteristics making it subtropical?

True. In this case though, keep in mind that this wasn’t even given a 10% chance in any TWO to become just a subtropical depression. The TWOs cover both tropical and subtropical depression+ development potential.

Keep in mind that this wasn’t even given a 10% chance in any TWO to become just a subtropical depression. The TWOs cover both tropical and subtropical depression+ development potential.

I’m not sure as it’s somewhat subjective. I’m thinking more about subtropical than tropical. But the NHC never even had it at a 10% chance to transition to subtropical or tropical in any TWO, which is what really made JB mad initially.

@snowman19This is related to what I was talking about. It’s not just the NE Pacific that’s so warm. It’s the entire N Pac., which isn’t necessarily even partially correlated to a cold winter in the E US like BAMwx and others are forecasting.

8AM TWO: getting very close now… Central Tropical Atlantic (AL92): Showers and thunderstorms associated with a broad low pressure area located about midway between the Windward Islands and the coast of west Africa have become better organized since yesterday. Environmental conditions are conducive for additional development, and a tropical depression or storm is likely to form in the next day or two as the system moves west-northwestward or northwestward at 10 to 15 mph over the central tropical Atlantic. * Formation chance through 48 hours...high...90 percent. * Formation chance through 7 days...high...90 percent.

Followup: Bastardi is livid that this hasn’t been named:

Bastardi is livid that this hasn’t been named:

Many are. And at least there’d be something interesting to follow with hopefully nobody needing to worry about potential devastation and casualties. I say hopefully nobody because there’s still some chance Bermuda will be hit. Fortunately though, Bermuda handles storms pretty well due to good elevation just off many of the beaches (hilly terrain) and very strict building codes. This includes limestone roofs! I’ve been there.

2022 was odd in that it ironically had the 10th highest Sept ACE of the current active era with way over the active era Sept avg ACE, but it also had the 3rd lowest ACE for Aug/Oct combined of the last 60 years behind only the super El Niños of 1997 and 1982.

Now 60/90: is the long drought about to be broken? Keep in mind though that 91L also made it to 60/90 along with strong model support and surprisingly never developed: Tropical Weather Outlook NWS National Hurricane Center Miami FL 800 PM EDT Mon Sep 15 2025 For the North Atlantic...Caribbean Sea and the Gulf of America: 1. Central Tropical Atlantic (AL92): A broad area of low pressure is located about midway between the Windward Islands and the coast of west Africa. This system is showing signs of organization, and is expected to move through a favorable environment for further development. A tropical depression or tropical storm is likely to form by the middle to latter part of this week while the system moves west-northwestward at 10 to 15 mph over the central tropical Atlantic. * Formation chance through 48 hours...medium...60 percent. * Formation chance through 7 days...high...90 percent. Forecaster Pasch

12Z UKMET: again has a followup MDR TC to Invest 92L (0Z actually had 2 followups): NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 156 HOURS FORECAST POSITION AT T+156 : 15.9N 37.2W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 22.09.2025 156 15.9N 37.2W 1012 31 1200UTC 22.09.2025 168 16.7N 39.4W 1011 32

12Z JMA completed (fwiw): Although the 72 hour map had it recurving NW seemingly way out in safe recurve land, it then turned W through 144 getting it to 21N, 62W (similar to Icon). Then it does a recurve WNW and then NW ending at 25N, 70W.

Tropical Weather Outlook NWS National Hurricane Center Miami FL Issued by the NWS Weather Prediction Center College Park MD 200 PM EDT Mon Sep 15 2025 For the North Atlantic...Caribbean Sea and the Gulf of America: Central Tropical Atlantic (AL92): A broad area of low pressure has formed roughly midway between the Windward Islands and the coast of west Africa. This system has become better organized since yesterday and is expected to move through a favorable environment for further development. A tropical depression or tropical storm is likely to form by the middle to latter part of this week as the system moves west-northwestward at 10 to 15 mph over the central tropical Atlantic. * Formation chance through 48 hours...medium...50 percent. * Formation chance through 7 days...high...90 percent. $$ Forecaster Blake/Putnam

12Z runs: -GFS/CMC favoring an H but well E of Bermuda -Euro is very close to but just NE of Bermuda with an H -Icon is well to the SW of those other 3 and it’s fate is still unknown at 180 with it a TS S of Bermuda just starting a NW recurve -12Z JMA out to 72 so far: TC moving NW way out there -12Z UKMET like prior run threatens Bermuda with this run aimed only a little E of there: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 54 HOURS FORECAST POSITION AT T+ 54 : 17.5N 46.9W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 18.09.2025 60 18.3N 47.8W 1007 41 1200UTC 18.09.2025 72 20.5N 50.5W 1007 43 0000UTC 19.09.2025 84 21.3N 53.4W 1007 41 1200UTC 19.09.2025 96 22.5N 55.5W 1007 31 0000UTC 20.09.2025 108 23.3N 57.0W 1007 32 1200UTC 20.09.2025 120 25.2N 58.1W 1007 38 0000UTC 21.09.2025 132 26.6N 58.4W 1004 44 1200UTC 21.09.2025 144 27.7N 60.4W 1002 41 0000UTC 22.09.2025 156 29.0N 61.7W 999 49 1200UTC 22.09.2025 168 30.6N 62.4W 995 51

Bastardi is mad that this isn’t being highlighted in the NHC TWOs so far. Remember the recent no name system that hit SE NC with extreme flooding along with TS force sustained winds? JB is still mad about that and I don’t blame him.