Tropical Wave has emerged from West Africa (Is Invest 95L)

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Spacecoast
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Re: Tropical Wave inside Africa

#181 Postby Spacecoast » Tue Sep 08, 2020 9:07 pm

It appears (to me) that it seems to be losing a little organization tonight...?
I may be wrong. It looked better this a.m. Now it looks more like 3 blobs.

The one behind this looks better now. It always seems like the 'next one' looks better.

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Re: Tropical Wave inside Africa

#182 Postby Hurricane Jed » Tue Sep 08, 2020 9:08 pm

TheStormExpert wrote:This wave future 95L will be the ultimate test to see if it can become a big ACE producer and a major hurricane as Paulette and Rene aren’t looking too great tonight. So far the ACE this season to date with the 17/5/1 are less than that of which Dorian alone produced last season if that puts things into perspective.


We could finish this season with less than 100 ACE and it really doesn’t matter. Not gonna take away the impacts of Cristobal, Hanna, Isaias and Laura.
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Re: Tropical Wave inside Africa

#183 Postby SconnieCane » Tue Sep 08, 2020 9:09 pm

supercane4867 wrote:Long range GFS in the MDR always underestimate the ridge. I can’t remember one single scenario that it didn’t.


...and the EURO always overestimates it, although usually not in the short-range to the extent that it and its ensembles did in insisting on sending Laura to Galveston. It's usually more like in the case of Irma, where it put it a little deeper into Cuba than actually transpired before hooking north to Florida.
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Re: Tropical Wave inside Africa

#184 Postby ClarCari » Tue Sep 08, 2020 9:10 pm

Spacecoast wrote:It appears (to me) that it seems to be losing a little organization tonight...?
I may be wrong. It looked better this a.m. Now it looks more like 3 blobs.

The one behind this looks better now. It always seems like the 'next one' looks better.

https://i.ibb.co/JyPx9wS/animate.gif


It doesn’t matter what it does over land. haha Those 3 blobs no matter how they look will consolidate quickly on splashdown.
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Re: Tropical Wave inside Africa

#185 Postby DestinHurricane » Tue Sep 08, 2020 9:12 pm

SconnieCane wrote:
supercane4867 wrote:Long range GFS in the MDR always underestimate the ridge. I can’t remember one single scenario that it didn’t.


...and the EURO always overestimates it, although usually not in the short-range to the extent that it and its ensembles did in insisting on sending Laura to Galveston. It's usually more like in the case of Irma, where it put it a little deeper into Cuba than actually transpired before hooking north to Florida.


GFS overdoes troughs much more than Euro overdoes ridges. And i've seen plenty of times Euro does not overdo ridge. Your assertion that it ALWAYS does just isn't true. It's the UKMET that almost always overdoes ridging.
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Re: Tropical Wave inside Africa

#186 Postby Fancy1001 » Tue Sep 08, 2020 9:27 pm

in the gfs 18z, are the remnants of Rene pulling sally northward preventing it from heading into the northern Caribbean, or is it preventing sally from going more out to sea sooner and being pushed closer to the US?
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Re: Tropical Wave inside Africa

#187 Postby ConvergenceZone » Tue Sep 08, 2020 10:28 pm

I think this will recurve, and the reason is that I just don’t see this staying weak especially since it already looks so good
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Re: Tropical Wave inside Africa

#188 Postby ClarCari » Tue Sep 08, 2020 10:39 pm

I think at most it will do a recurve only slightly farther out than where Matthew‘s track was. Right now it’s looking like it’s going too south to recurve any farther than that.
We can only hope it stays out at least that far, but unfortunately the Eastern Caribbean could still very easily get pummeled by a major from this storm.
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Re: Tropical Wave inside Africa

#189 Postby USTropics » Tue Sep 08, 2020 11:06 pm

Fancy1001 wrote:in the gfs 18z, are the remnants of Rene pulling sally northward preventing it from heading into the northern Caribbean, or is it preventing sally from going more out to sea sooner and being pushed closer to the US?


In the 18z GFS forecast, Rene acts to erode the eastern periphery of the CATL ridge, which allows this AEW to track more north.

Image

You can see this evolution in the 4 run trend:

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One of the reasons for this is the GFS was way too ambitious on Rene's short-term evolution compared to the other model outputs:
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A stronger Rene in the short-term meant it was in a better position to handle the shear in 3-5 days, and thus hangs around for quite some time. The 00z GFS is coming in with a much weaker Rene, so we're likely to see another separate solution from this run.
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Re: Tropical Wave inside Africa

#190 Postby Hurricaneman » Tue Sep 08, 2020 11:43 pm

Is it me or from 168hrs to 222hrs on the 0zGFS is heading into a ridge instead of around it, may have to look at the ensembles for better clarification

Also the 0zGFS seems to follow the low level flow which has a weakness which makes no sense, a cat 2 hurricane doesn’t use the low level flow for steering but more the 500 flow which is more West
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Re: Tropical Wave inside Africa

#191 Postby AxaltaRacing24 » Tue Sep 08, 2020 11:50 pm

Hurricaneman wrote:Is it me or from 168hrs to 222hrs on the 0zGFS is heading into a ridge instead of around it, may have to look at the ensembles for better clarification

Also the 0zGFS seems to follow the low level flow which has a weakness which makes no sense, a cat 2 hurricane doesn’t use the low level flow for steering but more the 500 flow which is more West

it does this for every storm this strength. it plowed irma through ridges a hundred times.
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Re: Tropical Wave inside Africa

#192 Postby USTropics » Wed Sep 09, 2020 12:00 am

This is just for instructional purposes, again use the ensembles past 5 days. On the 00z GFS, while Rene is weaker, it's still having an influence on steering. You can see here at about 180 hours the AEW is able to just get tucked underneath the ridge. However, there are essentially canceling steering currents. Low-mid level flow is towards the west (blue) however upper-level flow is towards the north (red). Since the GFS has a deeper depiction on this run, there is a bit more of a northerly influence (stronger systems want to shoot for lowering pressures). This causes the system to slow down. You can see this occurring with the wind barbs in the GFS sounding as well.

Image

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Switching over the Weathermodels (TT stops running at 228 hours recently every run), this interaction is again occurring with the remnants of Paulette as it's absorbed in the jet stream, just creating this slight northerly flow (which is the reason the storm is essentially plowing into the high pressure area on this run):

Image

All of this acts to really slow down the forward speed of this system and give it a more northerly component. The main concern at this point is a system that does not develop as quickly would have a faster westward speed, which could allow it be positioned under the high pressure area and in a more dangerous position. We'll see how many ensemble members point to that scenario still.
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Re: Tropical Wave inside Africa

#193 Postby Fancy1001 » Wed Sep 09, 2020 12:33 am

Is the GFS delayed again?
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Re: Tropical Wave inside Africa

#194 Postby Extratropical94 » Wed Sep 09, 2020 12:42 am

A tropical wave is forecast to emerge off the west coast of Africa
on Thursday. Gradual development is expected once the system moves
over water, and a tropical depression is likely to form late this
week or over the weekend while the system moves generally westward
across the eastern tropical Atlantic.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...high...80 percent.
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Re: Tropical Wave inside Africa

#195 Postby USTropics » Wed Sep 09, 2020 2:02 am

If you were looking for consistency from the ECMWF operational, you're not going to get it with this run. EATL ridge breaks down, and the AEW is pulled north towards this. Here is the 120 hour 500mb forecast showing that break in the ridge (purple is this AEW, blue is Rene, and green is Paulette).

Image

Paulette then strengthens and recurves quickly, which allows for this AEW to follow it on the recurve. Oddly, Rene goes from the farthest east system to getting shunted westward towards Puerto Rico and becomes the farthest westward system (albeit heavily sheared) at the end of the run:

Image
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Re: Tropical Wave inside Africa

#196 Postby USTropics » Wed Sep 09, 2020 2:16 am

ECMWF ensembles out to 120 hours and some noticeable differences this run already. Rene is basically dissipated by all but 1 ensemble member. The AEW coming off Africa is still slow to develop on most members, but we're also seeing a slow down on some of the members in forward speed and a more northerly location at 120 hours (compared to previous ensemble runs).

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This basically created 2 camps. A more forward speed means the AEW gets trapped under the ridge over the CATL and threatens the Caribbean. A slower/more developed wave is influenced by the break in the ridge:
Image
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Re: Tropical Wave inside Africa

#197 Postby USTropics » Wed Sep 09, 2020 2:36 am

ECMWF ensembles at 300 hours, the spread is on from Central America up to the NE states:

Image
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Re: Tropical Wave inside Africa

#198 Postby cycloneye » Wed Sep 09, 2020 6:13 am

A tropical wave axis is inland over Africa along 07W/08W, moving W
at 10-15 kt. A 1009 mb low pressure area is along the wave near
12N. Scattered moderate convection is noted well out ahead of the
wave including within 240 nm of the W coast of Africa from 05N-
14N. Gradual development is expected once the system moves
over water, and a tropical depression is likely to form late this
week or over the weekend while the system moves generally
westward across the eastern tropical Atlantic. This area has a low
probability of tropical cyclone development in the next 48 hours.
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Re: Tropical Wave inside Africa

#199 Postby TheStormExpert » Wed Sep 09, 2020 6:43 am

00z Euro sends this on a very similar track to Rene off into the far NE Atlantic with potentially affecting the Azores. Meanwhile the latest 06z GFS has this recurving much further west while potentially affecting Bermuda, SE Canada or the NE U.S.
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Re: Tropical Wave inside Africa

#200 Postby SouthFLTropics » Wed Sep 09, 2020 6:45 am

Looks like the 06z GFS is up to its old tricks again...plows it right into a ridge. Not seeing what erodes the ridge here. Maybe I’m just missing it.


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