ATL: ISAIAS - Post-Tropical - Discussion

[USTropics]

Dolly 2008:


Irene 2011:

[Hurricaneman]

My new thoughts after the new model suite

I believe a track through the NE Lesser Antilles and just north of Puerto Rico and Hispaniola seems most likely and a track through the Bahamas and into Cocoa Beach Fl is my best guess heading north to the Carolinas

As for intensity I think I was too aggressive and am more in line with the models

24hrs TS. 40mph
48hrs. TS. 65mph
72hrs. TS. 70mph
96hrs. TS. 65mph
120hrs TS 50mph
144hrs TS. 65mph

Next forecast 11am

[Hammy]

Can anyone think of another invest that looked even remotely like this one in this location? Not only is it absolutely massive, but it has a vigor that I've never seen, and has been tapping into moisture streams all the way from the equator. With the current climatology and amount of dry air that was around this system, I think that any smaller wave would have been completely consumed.

A bit late to answer but I found four in particular came to mind (there were probably others but I'd have to go into the 1980s to look)--Bonnie, 1998 spanning from 7N to 18N; a non-developing wave in 2000 spanning from about 5N to 18N (listed as a TD in my log nonetheless), Irene in 2011, spanning from 5N to 17N, and Cristobal in 2014 spanning from 5N to 20N and taking a similar track that this one is expected to (that one finally developed in the Bahamas, under similar circumstances, interacting with a PV streamer and going out to sea)





Interestingly 75% of them developed which matches 92L's development chances.

[CyclonicFury]

Can anyone think of another invest that looked even remotely like this one in this location? Not only is it absolutely massive, but it has a vigor that I've never seen, and has been tapping into moisture streams all the way from the equator. With the current climatology and amount of dry air that was around this system, I think that any smaller wave would have been completely consumed.

A bit late to answer but I found four in particular came to mind (there were probably others but I'd have to go into the 1980s to look)--Bonnie, 1998 spanning from 7N to 18N; a non-developing wave in 2000 spanning from about 5N to 18N (listed as a TD in my log nonetheless), Irene in 2011, spanning from 5N to 17N, and Cristobal in 2014 spanning from 5N to 20N and taking a similar track that this one is expected to (that one finally developed in the Bahamas, under similar circumstances, interacting with a PV streamer and going out to sea)

https://i.imgur.com/Tlzn5Oo.png

https://i.imgur.com/DjJTAP0.png

Interestingly 75% of them developed which matches 92L's development chances.

These large waves tend to happen most commonly in late July/August when the West African Monsoon is near peak. During September, when the WAM starts to retreat, it seems like the TWs become more compact, allowing more of them to develop.

[Hammy]

Can anyone think of another invest that looked even remotely like this one in this location? Not only is it absolutely massive, but it has a vigor that I've never seen, and has been tapping into moisture streams all the way from the equator. With the current climatology and amount of dry air that was around this system, I think that any smaller wave would have been completely consumed.

A bit late to answer but I found four in particular came to mind (there were probably others but I'd have to go into the 1980s to look)--Bonnie, 1998 spanning from 7N to 18N; a non-developing wave in 2000 spanning from about 5N to 18N (listed as a TD in my log nonetheless), Irene in 2011, spanning from 5N to 17N, and Cristobal in 2014 spanning from 5N to 20N and taking a similar track that this one is expected to (that one finally developed in the Bahamas, under similar circumstances, interacting with a PV streamer and going out to sea)

https://i.imgur.com/Tlzn5Oo.png

https://i.imgur.com/DjJTAP0.png

Interestingly 75% of them developed which matches 92L's development chances.

These large waves tend to happen most commonly in late July/August when the West African Monsoon is near peak. During September, when the WAM starts to retreat, it seems like the TWs become more compact, allowing more of them to develop.

Something of note that I just realized is all four instances preceded a burst of waves developing by a few weeks--1998 was August 18 and we had a burst in mid-September with Georges, Ivan, and Jeanne; 2000 was around September 7 and there was a burst around late September with Isaac and Joyce along with several stronger waves (but it was getting into October by this point so upper conditions were decreasing), 2011 was Aug 19 which was followed similarly to 2000 by Ophelia and Philippe before the MDR shut down in October; and despite 2014 being very quiet overall, we saw long-tracking Edouard along with a few other strong waves (eaten by shear) about three weeks after Cristobal's massive precursor wave.

Not that it means much having only four examples, but some food for thought.

Edit: Just scrolled up, I'm not the only one that thought of Irene by the looks of it.

[NotSparta]

Chances back up to 80/90

Shower activity associated with a low pressure area located about
750 miles east of the Windward Islands is gradually increasing
in organization. However, recent satellite-derived wind data
indicate that the circulation remains broad and elongated, and the
low does not yet have a well-defined center of circulation.
Environmental conditions are expected to become somewhat more
conducive for development, and a tropical depression or tropical
storm is likely to form during the next couple of days while the
system moves west-northwestward at 15 to 20 mph and approaches the
Leeward Islands. Regardless of development, locally heavy rains and
gusty winds are likely across portions of the Leeward Islands on
Wednesday and will spread westward to the Virgin Islands and Puerto
Rico Wednesday night and Thursday. Interests on these islands
should continue to monitor the progress of this system, and
tropical storm watches or warnings could be required for portions
of the area later today.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.

[Hammy]

They really need to issue PTC advisories at this point, given the size and intensity forecasts this will almost certainly go through the Caribbean at mid-range storm intensity even if it hasn't technically developed yet.

[HurricaneAndre2008]

[CM2]

So after all the talk about 92L possible not being a storm, the ECMWF, HMON, and HWRF have all radically changing their stances and now have a pretty damn strong storm for the 00z run and a FAR western turn. I believe this kind of flips everything on it's head. Now we're talking about a cat 2/3 off the shore of Miami and potentionally hitting the Bahamas stright on. Jesus.

[AxaltaRacing24]

So after all the talk about 92L possible not being a storm, the ECMWF, HMON, and HWRF have all radically changing their stances and now have a pretty damn strong storm for the 00z run and a FAR western turn. I believe this kind of flips everything on it's head. Now we're talking about a cat 2/3 off the shore of Miami and potentionally hitting the Bahamas stright on. Jesus.
https://imgur.com/XA3Kv9n
https://imgur.com/Ssb7Xcv
https://imgur.com/WMvj2dV

As I said earlier, I have not seen the models this bad since I joined this forum in 2016.

This is not much better than 2000s modeling.

[CM2]

So after all the talk about 92L possible not being a storm, the ECMWF, HMON, and HWRF have all radically changing their stances and now have a pretty damn strong storm for the 00z run and a FAR western turn. I believe this kind of flips everything on it's head. Now we're talking about a cat 2/3 off the shore of Miami and potentionally hitting the Bahamas stright on. Jesus.
https://imgur.com/XA3Kv9n
https://imgur.com/Ssb7Xcv
https://imgur.com/WMvj2dV

As I said earlier, I have not seen the models this bad since I joined this forum in 2016.

This is not much better than 2000s modeling.

I did make a public decry that the models are all officially Bananas. Still even in that case the trend is important because changes between runs do occur for a reason (I hope.)

[Shell Mound]

 https://twitter.com/webberweather/status/1287810518758105091



 https://twitter.com/webberweather/status/1287812146018037761



 https://twitter.com/pppapin/status/1287818663115055105



 https://twitter.com/AndyHazelton/status/1287820813572464640



 https://twitter.com/AndyHazelton/status/1287824931170979841

[Hurricane Mike]

https://twitter.com/webberweather/status/1287810518758105091
https://twitter.com/webberweather/status/1287812146018037761
https://twitter.com/pppapin/status/1287818663115055105
https://twitter.com/AndyHazelton/status/1287820813572464640
https://twitter.com/AndyHazelton/status/1287824931170979841

92L's "struggling". What "struggling"? I see an extremely impressive wave that has been looking better and better for 12 hrs.

[GCANE]

This is essentially a broad gyre with a massive amount of entrained moisture (high TPW air).
Interaction with one of the small islands or a brush with PR could consolidate a low-level vort due to boundary layer frictional effects.
Basically creating a meso-scale convergence.
It'll likely move into the Bahamas and under an anti-cyclone.
IMHO, we could see more development then.

[GCANE]

A below the belt blow?

GFS is hinting at the possibility that if this doesn't develop in the Bahamas or remains weak, the wave will continue west, consolidate in the W Carib and move into the GOM with possible development.

At this point, its a TX / LA landfall.

Looks like one way or the other, something is going to happen.

[GCANE]

This is essentially a broad gyre with a massive amount of entrained moisture (high TPW air).
Interaction with one of the small islands or a brush with PR could consolidate a low-level vort due to boundary layer frictional effects.
Basically creating a meso-scale convergence.
It'll likely move into the Bahamas and under an anti-cyclone.
IMHO, we could see more development then.

All the globals are on this scenario.
Its basically a given.

[GCANE]

[STRiZZY]

A below the belt blow?

GFS is hinting at the possibility that if this doesn't develop in the Bahamas or remains weak, the wave will continue west, consolidate in the W Carib and move into the GOM with possible development.

At this point, its a TX / LA landfall.

Looks like one way or the other, something is going to happen.

https://i.imgur.com/Pi5TtWn.png

https://i.imgur.com/LPzf8M4.png

The GFS takes 92l through the Bahamas and runs it up the FLA/GA/SC coast. I think the system hitting LA at 300hr isn't a part of 92l.


You can see what becomes of 92l off the FL space coast and the system that ends up hitting LA is NW of Jamaica, S of Cuba on this vorticity map.

[GCANE]

A below the belt blow?

GFS is hinting at the possibility that if this doesn't develop in the Bahamas or remains weak, the wave will continue west, consolidate in the W Carib and move into the GOM with possible development.

At this point, its a TX / LA landfall.

Looks like one way or the other, something is going to happen.

https://i.imgur.com/Pi5TtWn.png

https://i.imgur.com/LPzf8M4.png

The GFS takes 92l through the Bahamas and runs it up the FLA/GA/SC coast. I think the system hitting LA at 300hr isn't a part of 92l.

https://www.tropicaltidbits.com/analysis/models/gfs/2020072800/gfs_z850_vort_watl_35.png
You can see what becomes of 92l off the FL space coast and the system that ends up hitting LA is NW of Jamaica, S of Cuba on this vorticity map.

Its the remnant of the wave currently associated with 92L.
Follow the MSLP & PWAT forecast.
PWAT is the same as TPW. Its what you would see on CIMSS's MIMIC-TPW.

[GCANE]

GFS is keeping this weak in the Bahamas due to the fact it'll be running into an UL Jet from a Rossby wave over the Midwest.
The Rossby Wave (Jet Stream) is the one creating the trof that will make it lift and recurve.
The closer it gets to the Rossby wave, the weaker it gets and the possibility of a GoM system increases.
If it slows down, it'll remain more under the Anticyclone Rossby Wave Break and develop stronger, which lessens the chance of a GoM TC.