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Tropical Wave just off Africa as of 9/2/20: something to monitor in SE for midmonth

GaWx

GaWx

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Because there is some chance that this impacts the SE in ~2 weeks (see my next post) even though it could still end up recurving well OTS or bypass the SE and hit the NE, I've decided to go ahead and add a new thread for this wave that just emerged from Africa. This wave is not Invest 91L (which is in yellow on the TWO map) as this one has yet to be assigned an invest. Here's the part of the latest TWO addressing this with the accompanying map showing the wave in orange:


Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Wed Sep 2 2020

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

2. A tropical wave, located just off the coast of west Africa, is
producing limited shower activity. The wave is expected to merge
with a disturbance centered a couple of hundred miles southeast of
the Cabo Verde Islands toward the end of the week. Gradual
development of this system is then possible, and a tropical
depression could form over the weekend while it moves westward over
the eastern and central tropical Atlantic Ocean.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...medium...60 percent.

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I’ve been warning about mid Sept over the last few days for a potentially dangerous setup for the SE soon after the cooler Canadian air comes in either from an MDR wave or from a homegrown (similar to Diana of 1984). The worry is increased due to the combo of the very warm Indonesian waters, La Niña, and the +AMO, all of which increase the chance for the WAR to be strong with the W extension pretty far west and further west than many of the model runs were showing. Well, lo and behold, look at the ominous looking 12Z GEFS at 288 (for Sept 14), an almost textbook dangerous pattern at H5 along with the big NE US high. Then look below at the individual members for that time and then for 3 days later (Sept 17). By the end of the run, a whopping 7 of 21 members (33%) hit various parts of the SE with a H by Sep 18 o_O :

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As mentioned, this obviously can still easily recurve well OTS. Whereas the 12Z GEFS was ominous for the SE with a whopping 33% of members hitting with a H, the 12Z EPS has only one member (2%) that ever gets close to the US with it in the Bahamas at 312 followed by a move W into S FL. The ones well E recurve way OTS and the 2 in the GOM are not from this:

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I should add that the 12Z Para GEFS is in between these two threat-wise with some SE hits but with many recurving OTS due to much further E WAR vs the 12Z GEFS. Also, the 12Z GEPS says recurve well OTS for the same reason.
 
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I would think a lot depends on how fast it develops

If it struggles that's actually probably a bigger threat and the trend this year has been to not develop til later
 
We will see but it’s way too soon to know. With that said I will say the majority of all systems recurve or are not big disasters so that’s what’s currently going against this thread.
 
The 18Z GEFS is fairly similar to the 12Z with the WAR but it isn't quite as bad as 12Z with 5 SE sub 1,000 mb hits vs 7 on the 12Z., 5 on the 6Z, and 1 on the 0Z. The 18Z had more far OTS members than the 12Z and 6Z.

18z Euro finishes at hour 90 a little E of the 12Z. The further E the sfc low, the better for us because it increases the OTS chances. 18Z EPS not out yet.

Update: the 18Z EPS, which goes out thru 144, is E of recent runs with many features.
 
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GaWx said:
The 18Z GEFS is fairly similar to the 12Z with the WAR but it isn't quite as bad as 12Z with 5 SE sub 1,000 mb hits vs 7 on the 12Z., 5 on the 6Z, and 1 on the 0Z. The 18Z had more far OTS members than the 12Z and 6Z.

18z Euro finishes at hour 90 a little E of the 12Z. The further E the sfc low, the better for us because it increases the OTS chances. 18Z EPS not out yet.

Update: the 18Z EPS, which goes out thru 144, is E of recent runs with many features.
Click to expand...

For the SE US. the 0Z GEFS of 9/3 is more benign with only 1 member landfalling and 2 others skirting NC to 5, 7, and 5 landfalls for the prior three. OTOH, the NE US is more threatened on this run.
 
Honestly I don’t trust much of what the models are saying for anything in the MDR .. with the lack of overseas data from the lack of air travel, more than likely were dealing with a very poor medium to long range forecast from models .. just not enough upper air data ..until they are surveyed and missions go out observing and collecting upper air data we can’t believe we have any sort of clear picture on what’s to come of these storms
 
00z Euro, 00z ICON, 00z CMC and 06z GFS ...... appears they agree on 9/10 for the first storm, but Euro is faster which could have a different result due to timing.

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ScreenshotCapture_2020_09_03_08_05_10_576.jpgScreenshotCapture_2020_09_03_08_09_12_526.jpg
 
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Nick_boynton_ said:
Honestly I don’t trust much of what the models are saying for anything in the MDR .. with the lack of overseas data from the lack of air travel, more than likely were dealing with a very poor medium to long range forecast from models .. just not enough upper air data ..until they are surveyed and missions go out observing and collecting upper air data we can’t believe we have any sort of clear picture on what’s to come of these storms
Click to expand...
I think we all agree with you why isn’t all of this is the general hurricane thread? Every storm should be monitored for the s/e anyways
 
BirdManDoomW said:
I think we all agree with you why isn’t all of this is the general hurricane thread? Every storm should be monitored for the s/e anyways
Click to expand...

I have been confused to where to post of lately. I may just stay in general discussion board for tropical development until a depression is named.


Sent from my iPhone using Tapatalk
 
I wouldn't write off a lot regarding the Atlantic at the moment. Any changes in the strength/placement of the upper low, changes in the strength of the potential systems, timing changes with the potential systems will have a massive impact on the end game.
 
Need to watch for cold front development closer to home if they actually make it through NC. It’s getting to the that time of year where we should look for Bahamas development and Gulf of Mexico
 
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