WxWatcher007

Tropical Storm Erin Discussion Number 5 NWS National Hurricane Center Miami FL AL052025 1100 AM AST Tue Aug 12 2025 Erin still has a well-defined low-level circulation, but the convective pattern has degraded since overnight, with only a band of moderate convection located within the southern part of the circulation. A 1226 UTC ASCAT-C pass showed a maximum wind barb of 36 kt north of the center, and the intensity is held at a possibly generous 40 kt. Most likely, this is a result of Erin's fast motion, which has been south of due west (265 deg) at about 20 kt. The guidance suite indicates that Erin may continue to lose some latitude during the next 24 to 36 hours due to strong low- to mid-level ridging over the eastern and central Atlantic, but overall the general motion should be westward through early Thursday. After that time, indications are that the ridge may weaken over the western and central Atlantic, causing Erin to turn west-northwestward, but there are model discrepancies on when that might happen and where the break in the ridge actually forms. The trend has been for a weaker Erin in the short term and possibly a stronger ridge, and a number of track models, including HAFS-A and -B, HWRF, the European, HCCA, and the Google Deep Mind, have shifted south and west for much of the 5-day forecast. The NHC forecast has shifted in that direction accordingly, and it should be noted that a significant number of deterministic models and ensemble members still lie even farther south. The environment of marginal water temperatures (26-27 deg Celsius) and low atmospheric instability and moisture appear to remain nearly constant for the next 24 hours or so. Therefore, little to no intensification is expected through early Wednesday. The environment and water temperatures become much more suitable for strengthening by 48 hours, and since the cyclone already has a well-defined structure, it could become a hurricane by late Thursday. Continued strengthening is forecast after that time, and the NHC forecast continues to show Erin becoming a major hurricane by day 5 (early Sunday). There is quite a lot of spread in the intensity models, and the NHC prediction is in the upper regime of the envelope, close to the SHIPS model, Florida State Superensemble, and ICON intensity consensus. KEY MESSAGES: 1. Although it is still too early to know exactly what impacts Erin might bring to the northern Leeward Islands, the Virgin Islands, and Puerto Rico, the risk has increased for Erin to move closer to these islands over the weekend. Interests there should monitor the progress of this storm. 2. There is even greater uncertainty in what impacts, if any, might occur in portions of the Greater Antilles, the Bahamas, the east coast of the United States, and Bermuda next week. As we approach the climatological peak of the hurricane season, this is an opportune time to ensure your preparedness plans are in place. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 17.2N 36.3W 40 KT 45 MPH 12H 13/0000Z 16.8N 39.1W 40 KT 45 MPH 24H 13/1200Z 16.5N 42.3W 40 KT 45 MPH 36H 14/0000Z 16.6N 45.2W 45 KT 50 MPH 48H 14/1200Z 17.1N 48.3W 55 KT 65 MPH 60H 15/0000Z 17.8N 51.3W 65 KT 75 MPH 72H 15/1200Z 18.5N 54.4W 75 KT 85 MPH 96H 16/1200Z 19.8N 60.3W 90 KT 105 MPH 120H 17/1200Z 21.4N 65.0W 100 KT 115 MPH $$ Forecaster Berg

That's a lot ot get rid of lol

You don't need to look far to see why Erin is struggling convectively this morning. First, it's still in a marginally favorable SST environment Second and more important, it is plowing into an area of drier, more stable atmospheric conditions--something that was anticipated days ago. The microwave image I posted last night was illustrative of its organization, which still exists this morning. Note the well defined center and its symmetrical nature. Note also the more stable conditions to its northwest. This should keep Erin in check for a bit, but given the internal organization, if that doesn't fade once this finds a more favorable environment it should still be primed to ramp up. As for track, I still think it's highly unlikely to directly impact the US coast, but Atlantic Canada should be monitoring more closely.

The maritimes have been on a generational run. Seriously.

And once the system becomes convectively active again (as it did last night in the southern part of the system) we’ll have to see if that tugs the LLC in one direction or another temporarily.

It’s underdispursive but you get the picture.

I know tropical is an imby sport to most here, but some do forget that we have Atlantic Canada posters too. While the pattern isn’t conducive for the EC, the maritimes have more wiggle room and NS and especially Newfoundland are still squarely in watch territory right now. The exact parabolic curve matters to them.

I mean…this says it all.

Pretty well organized despite the marginal SSTs

The Atlantic ridging may actually be doable. Erin has been south of modeled so far and the trend toward a stronger ridge seems to have some legs (though the GFS was always underdoing it imo). The issue is later--that UL steering pattern over the EC in the long range is anything but a NE landfall look--as folks have said. If that massive trough in Canada can be blunted and the ridging in the Atlantic continues to look stronger...then maybe we're talking.

The trend today has been a further south track and that seems more plausible given the convective trend tonight with Erin but generally agree. Still a long way to go.

Just pointing out the potential. Atlantic Canada has been on an exceptional run of hits from recurving TCs. I'm not sure historic is the word, but it would be very hard to do given where we are now. Keep in mind that the general trend today has been a further south track in the short term, and we don't know what that means long term given the uncertainty on how amplified the Atlantic ridge is and the depth of whatever troughing comes out of the eastern US/Canada.

Remember that you need two huge changes to occur: 1) the Atlantic ridge is substantially stronger for longer to push Erin deeper into the SW Atlantic AND 2) A cutoff trough at the right time to pull it up the coast, which also requires that Canadian troughing showing up in the long range across guidance to essentially be replaced with a ridge or at least something that isn't screaming NW flow. Not impossible, but that is a very tall task. @CoastalWxwe go all winter and summer with ridges, SW flow, and trough de-amplification and as soon as there's a tropical system that all goes poof. San Diego

I was a little surprised by that given the op but clearly some other members put Atlantic Canada in play (for this run)

18z GFS more in line with Euro. I do wonder how much more change that ridge can take. Again, even if it means nothing for us (likely) if there is troughing diving to our west that opens the door for Hazey and the crew.

Yes. That massive trough the Euro is toying with will kick this if that materializes (and it’s unclear if it will to that extent)

I think a direct U.S. impact is increasingly unlikely, but not fully closed. Worth a closer in Bermuda and Atlantic Canada imo.

I still think the GFS and its ensembles are too fast with the Atlantic ridge weakness, but we’d need substantial changes at medium range just to be a long shot in the ballgame for a close EC approach (saying nothing of the maritimes).

Just a monster. I mean look at this. 12z And 00z Life support is probably putting it kindly though watch out Atlantic Canada..

Sad to hear that but congrats on grad school! I still kick around the idea of going back for a met degree but I think that ship has sailed. Maybe some sort of a certificate though to enhance my forecasting knowledge.

Let’s get the pick ‘em going!

Yes, folks here are always too quick to cancel, but we gotta be honest—you would need a lot to happen to make this a bona fide EC threat that this point. You will see this on ensembles—which are the better option for analysis—but I’m using the op because it’s easier to see. The troughing signal to our west is obviously important to having any chance but it’s poorly timed, poorly positioned, and too slow to cut off. That can change at this range but that’s a secondary issue. The first and most fundamental issue is that the weakness in Atlantic ridging is happening way way way too early. It’s basically turning near Bermuda. That weakness isn’t out in weenie range. And while to Pope’s point it can change (and I think the GFS is too early with the weakness), whenever you’re asking a lot of the steering conditions in tropical, it usually doesn’t work out. So while it’s not over technically, the odds of a U.S. hit are looking increasingly small imo. Last thing I’ll say though is that even with the super ensemble the longer range members tend to be underdispursive. If that troughing in the eastern US is real I’d watch in Atlantic Canada. They’ve actually done exceptionally well with these kind of setups in recent years.

I mean...that's a TC to me. SHIPS has continued to get more aggressive with development, and now has this becoming our first major hurricane of the year in a few days when it reaches a more favorable environment. 97L is getting an upper level assist from a passing CCKW, but heat content and SSTs will significantly improve further west. That said, note the drier air ahead of it though. It may impact its ability to intensify despite its current IR display.

The next time Wiz complains about every swirl getting named by the NHC I'll just show him this. IR, surface obs, and sat wind estimates have had this a TC for a good portion of the day.

I really like using a “super ensemble” to visualize what’s being modeled, and Tomer has a great site that shows the trend over time.