Tropical Wave in the Central Atlantic (10/60)

[chris_fit]

12z EURO AI follows Erin OTS

[SFLcane]

It depends on the weather patterns each year, this year central and north Florida have gotten a reasonable amount of afternoon thunderstorms but SE Florida has been pretty dry. Last year was pretty wet across central FL, 2023 was a very dry year. Here's the current drought map (note that this is an improvement from a few weeks ago):

 https://x.com/FloridaTropics1/status/1956361524357775644

I am the NWS coop for lake worth and i can tell you there has been not much of any improvement in metro se florida i have recorded a little over an inch of rainfall in the last 25 days at my coop site. We need the rain!

Mine:

https://dex.cocorahs.org/stations/FL-BW-159

https://adriansweatherstation.com/

Rainfall is measured with NWS 20 inch SRG. i have 2 manual gauges.

https://adriansweatherstation.com/about.php

[ConvergenceZone]

A couple of people mentioned needing the rain from a tropical storm and that it hardly rains in SE Floriday anymore, but don't you guys still get afternoon thunderstorms? I visited the Miami area a couple of summers back and almost every afternoon there were thunderstorms popping up with some pretty crazy downpours.

There has been a ridge in place since early June with a few weak troughs but we have a 14+ inch deficit in Fort Lauderdale. We dont even get clouds to tale the edge off, its more like Palm Springs than Palm Beach.

oh man that's terrible that you guys don't even get random thunder showers anymore. Well hopefully this be a weak tropical storm, but enough to give you guys a good soaking rain.

[boca]

I posted earlier that it’s rained maybe 5 times since January and the rainy season never kicked in down here. The easterly flow pushes everything to the west coast and we are high n dry.

[Stratton23]

Now up to 10/60.It should be an invest at some point later today, not really giving much weight to the global models since i strongly believe they are not not seeing the southern side of this wave really well at all

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Mon Aug 18 2025

Tropical Atlantic:
A tropical wave located over the eastern tropical Atlantic is
producing limited disorganized showers and thunderstorms.
Environmental conditions appear conducive for gradual development of
this system, and a tropical depression could form toward the end of
the week. This system should move westward to west-northwestward at
about 20 mph across the central tropical Atlantic and approach the
vicinity of the Leeward Islands on Friday.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...medium...60 percent.

[wzrgirl1]

Well some models are seeing something now that it is up to 60% in the 7-day time frame. I anticipate an invest by tonight.

[IcyTundra]

12Z Euro not budging on its weak and OTS track.

[cycloneye]

HAFS parent develops this.

 https://x.com/RyanMaue/status/1957503669466751482

[StPeteMike]

Now up to 10/60 now, should be an invest at some point later today, not really giving much weight to the global models since i strongly believe they are not not seeing the southern side of this wave really well at all

Agreed! Think once we get an invest going and the models are able to focus on one area instead of multiple areas, we will get a better grasp and better model runs of this future invest.

I think that close up of the AOI rotation is clear indication that the southern side will be the dominant side and will win out. The northern side is actually helping out by keeping the SAL from going further south and west and disrupting the eventual invest.

[BobHarlem]

The 12z Euro is not developing this either, and recurves the reflection just west of Bermuda. GFS operational and the ensembles (GFS and some euro) are really the only ones showing it right now. (This includes the Uk, Icon, and Canadian, which also don't show development)

[Nimbus]

Looks like they are waiting for this to make the latitude jump out of the ITCZ before calling an invest.
Still busy with Erin and there isn't a low level center yet.

[Stratton23]

That definitely isnt true at all, the gfs/ gefs are not alone, the EPS shows a split with members going into the gulf , impacting the SE us or going out to sea

[txwxwatcher]

The 12z Euro is not developing this either, and recurves the reflection just west of Bermuda. GFS operational and the ensembles (GFS and some euro) are really the only ones showing it right now. (This includes the Uk, Icon, and Canadian, which also don't show development)

Yep. The trend is your friend.

[Hurricaneman]

If that area at 9n forms instead we might be talking a Caribbean cruiser instead of an out to sea or east coast scrape, definitely could also take a track similar to Allen in 1980 or even Charley or Ivan in 2004 as opposed to a track similar to David like the GFS depicts

[USTropics]

Apparently it takes three to tango. I want to show how nuanced this process is, because it's quite fascinating and unknown what the end result will be here. Something models didn't really catch on to until yesterday was a third vorticity maxima at the mid-levels. I've highlighted the three areas observed here from earlier today in the 700mb CIMSS vorticity product:


Now let's see how this has progressed in ~10 hours to current analysis:


So not only do we have this sort of rotation around a common mid-point above with these three vorticity features, but models are trying to determine which area will become dominant. We've just analyzed the mid-levels in the product above, so what I'm going to do is keep the positional markers fixed at latitude and longitude, and we can look at three levels of the atmosphere:

850mb (low level):


Earlier referenced 700mb (mid level):


500mb (upper level):


So we can see:
1) our area highlighted in pink is quickly going to fade with no support at either the lower or upper levels
2) the purple circled vorticity feature has lower-level support but not much upper-level support
3) the blue circled vorticity feature is mainly supported at the upper levels

So how does all this play out on the model runs? I'm going to first include those same 3 markers for our three vorticity features and overlay it on the 12z GFS run for around the same timeframe as the CIMSS products we just analyzed:


Now I'm going to jump forward 24 hours, and we can see we still have two features remaining on the GFS run:


Keeping these positions fixed, we can look at the 06z ECMWF run, and see there is barely a reflection in the wind barbs for the area highlighted in purple:


This remains the key difference in the medium term track (more on the long term track soon) for this area of interest between the operational models—which vorticity maximum at the mid levels will become dominant. In 72 hours, the GFS favors the purple area, which initializes the system down near ~14N:


The ECMWF favors the blue area, which initializes the system near ~16N:


Now for the long-term track. Launching point is obviously critical in the mid-term, and a further south initialization like the GFS would definitely cause some concern for potential islands and CONUS impacts. Since this is 120+ hours out, we need to switch over to the ensembles, and this is where we see the GFS ensembles have been playing a bit of catching up over the past day. The model was initially much more aggressive with how quickly Erin would turn north and its transition to extratropical. This is the 5-day trend of the last 6 runs of the GFS ensembles, with each number reading being an ensemble member's position of Erin:


With the 12z data, the ensemble spread is significant with the position of Erin at even 5 days, and where Erin is in 5 days is going to have large implications on the future track of this system:


I want to show one more thing, which are the 12z spaghetti plots of the GFS ensemble members (and a broad spectrum of possible outcomes). This best illustrates that the path to a recurving system is not as clear as it was with Erin. A more southern position of initialization means this can still even track into the Gulf of Mexico. A quick turn to the north by Erin also shuts down the recurve alley. We can see even members that are major hurricane status are getting turned westward once the ridge slides back in behind Erin:

[StPeteMike]

If that area at 9n forms instead we might be talking a Caribbean cruiser instead of an out to sea or east coast scrape, definitely could also take a track similar to Allen in 1980 or even Charley or Ivan in 2004 as opposed to a track similar to David like the GFS depicts

I was trying to find similar tracks that could play out. Charley is a good example that even though troughs in August reaching the Gulf sounds far fetched, it’s not impossible!

[IcyTundra]

The 12z Euro is not developing this either, and recurves the reflection just west of Bermuda. GFS operational and the ensembles (GFS and some euro) are really the only ones showing it right now. (This includes the Uk, Icon, and Canadian, which also don't show development)

Yep. The trend is your friend.

There really hasn't been a trend. We are in the same place we have been for the past few days. The GFS has been showing a more western track compared to other models for multiple days in a row now and the Euro continues to show a more eastern track and is much weaker. We just have to wait and see what happens.

[Stratton23]

USTropics great analysis and read! Will be interesting to see which vort max wins out, bur it is interesting to see most of the convection is really favoring the purple circle that you have shown above in the post

[starsfan65]

USTropics great analysis and read! Will be interesting to see which vort max wins out, bur it is interesting to see most of the convection is really favoring the purple circle that you have shown above in the post

Where is the site at?

[Stratton23]

starsfan65 posts come from tropical tidbits and CIMSS tropical cyclones site