ATL: LAURA - Post-Tropical - Discussion

[Aric Dunn]

This looks like it will start to get interesting..

http://tropic.ssec.wisc.edu/real-time/atlantic/winds/wg8sht.GIF

There's a fair bit of mid-level shear though, and that hurts storms a lot more than upper-level shear.

yeah, should cross the mid level shear axis sometime tomorrow. but this SW shear is about to end.

[cheezyWXguy]

HWRF crushes key west at 942mb

[Hammy]

I've been staring at the satellite appearance that TD13 has taken on pretty much for the last half hour and trying to figure out why the overall pattern and setup looks so familiar, and checked my satellite archives:



After checking the CMC initialization history it appears this might be doing the same thing Hermine's invest did in 2016: the eastern portion from a few days ago is now rotating around to the north (the vortex we've been following)

[Shell Mound]

Really seems like the story the last decade, pretty much everything after 2010 with the exception of 2017--nothing can really seem to strengthen any until it's north of 20-25..

Matthew, Sandy, Rina, Ernesto (2012), Danny (2015), Otto, Beryl (2018), and Lorenzo would all like to say hello.

Though, there's a point to be had about the storms with tropical origins this year struggling with large or elongated CoCs. Seems like this year in the Atlantic has preferred the WPAC-style of massive tropical waves with multiple points of vorticity before consolidating.

I should've specified I meant the Atlantic MDR. It's certainly seen struggling storms that strengthen later (or dissipate) more often than not and it seems we've left the days where we can look at an Atlantic wave and be almost certain it will strengthen behind in the 1990s/2000s.

On the second point (as this happened in 2012 as well) I wonder if that's going to reduce the number of stronger hurricanes that we see this year, especially originating from easterly waves. 2012--which this season is feeling increasingly similar to--only had two majors, one of those was in the subtropics and the other in late October (which of course was Sandy) and all of hurricanes that originated in the Atlantic did so north of 20, if not north of 25.

I have a feeling you’re going to regret this statement by the time September is over. All the factors currently favour a hyperactive deep tropics.

Back to TD Thirteen...

[rigbyrigz]

HWRF crushes key west at 942mb

...a lot like Irma, even with the 24 hour zoom-up before the Keys. Ends up a little west of the Big Bend though at 936mb. Was at the Beach today water must be high 80's. Guess I will root for the GFS tonight.

[Hammy]

Was going to edit but took longer to put together than I expected (namely it kept saving it as a video rather than a gif)

[Jr0d]

We just had a squall in Key West with 50mph winds that took out half the island's power. Not a good omen for what might be here early next week. Obviously it had nothing to do with either depression, but it is an indicator of how volatile the waters are right now.

I did some storm shopping today and will do more tomorrow. I do not like this setup.

I now give Key West a medium chance of storm conditions. I fully expect evacuations ordered Saturday morning.

[otowntiger]

NHC track is now north of most guidance even after they shifted south according to 5am discussion. Also no real strengthening expected for Next day or two. Looking like less and less threat for the FL peninsula east side. Keys are still going to need to be alert. Northern/northeastern gulf now obviously the focus. NHC not too confident in intensity forecast for that area. Interaction with 14 a big factor. Apparently GFS and Euro predict it to degenerate due to dry air/shear/ land interaction?

[Shell Mound]

Also no real strengthening expected for Next day or two. Looking like less and less threat for the FL peninsula east side. Keys are still going to need to be alert, but looks to stay even south of there, and not real strong at that.

The only reason the NHC is conservative is the possibility of interaction with the Greater Antilles, which in my view is less likely than a track just north of the islands, given that all the latest reliable guidance is tightly clustered near the Keys by days three and four, and the HWRF, along with the CMC, has consistently handled the short-term intensity trends and movement(s) better than the GFS/ECMWF, yet continues to indicate rapid deepening into a major hurricane commencing once TD Thirteen passes north of Puerto Rico and nears/enters the extreme southeastern Bahamas. The overall trends are definitely favouring a stronger ridge and a stronger TD Thirteen in three to five days that tracks farther west before turning north, so it is more likely to enter the eastern Gulf of Mexico before making its turn. The only question regards the placement of mesoscale features as well as the locations of both TD Thirteen and TD Fourteen in three to five days. No one in South Florida or the Keys should be dismissing this system; neither should anyone along the eastern Gulf Coast of the U.S., much less anyone in the Bahamas. Since both TD Thirteen and TD Fourteen may become powerful hurricanes at the time of their closest approaches to each other, TD Thirteen could certainly move a bit farther north than currently indicated before turning, that is, strike closer to Miami rather than Key West while moving WNW across the peninsula to the west coast of the state near, say, Tampa Bay. Currently, I think both depressions could be major hurricanes by days four and five, which is why I wouldn’t dismiss northward adjustments to the track of TD Thirteen through the Bahamas while en route to South FL. I think Miami/Fort Lauderdale is as much in play as the Keys at this point. The key is that both systems are going to make landfall in the U.S. at some point. At this stage TD Thirteen would be less likely to make landfall north of South FL, given the strength of the ridge. As I mentioned, this system has a good opportunity to affect either South FL or the Keys as a potentially powerful hurricane.

Excerpt from the latest NHC discussion suggests interaction with the Greater Antilles and/or (more probably) TD Fourteen are the only possible negatives:

The dynamical models suggests the centers will become more vertically aligned around 36-48 h and that the shear should diminish. However, the system could be close to Hispaniola during this time, and be near Cuba thereafter, especially if it moves south of the forecast track. The upper-level winds over the Gulf of Mexico should be generally favorable for development if the cyclone doesn't get too close to Tropical Depression Fourteen. The possibilities range from the system degenerating to an open wave as seen in the GFS and ECMWF to a major hurricane as seen in the HWRF.

[jlauderdal]

Also no real strengthening expected for Next day or two. Looking like less and less threat for the FL peninsula east side. Keys are still going to need to be alert, but looks to stay even south of there, and not real strong at that.

The only reason the NHC is conservative is the possibility of interaction with the Greater Antilles, which in my view is less likely than a track just north of the islands, given that all the latest reliable guidance is tightly clustered near the Keys by days three and four, and the HWRF, along with the CMC, has consistently handled the short-term intensity trends and movement(s) better than the GFS/ECMWF, yet continues to indicate rapid deepening into a major hurricane commencing once TD Thirteen passes north of Puerto Rico and nears/enters the extreme southeastern Bahamas. The overall trends are definitely favouring a stronger ridge and a stronger TD Thirteen in three to five days that tracks farther west before turning north, so it is more likely to enter the eastern Gulf of Mexico before making its turn. The only question regards the placement of mesoscale features as well as the locations of both TD Thirteen and TD Fourteen in three to five days. No one in South Florida or the Keys should be dismissing this system; neither should anyone along the eastern Gulf Coast of the U.S., much less anyone in the Bahamas. Since both TD Thirteen and TD Fourteen may become powerful hurricanes at the time of their closest approaches to each other, TD Thirteen could certainly move a bit farther north than currently indicated before turning, that is, strike closer to Miami rather than Key West while moving WNW across the peninsula to the west coast of the state near, say, Tampa Bay. Currently, I think both depressions could be major hurricanes by days four and five, which is why I wouldn’t dismiss northward adjustments to the track of TD Thirteen through the Bahamas while en route to South FL. I think Miami/Fort Lauderdale is as much in play as the Keys at this point. The key is that both systems are going to make landfall in the U.S. at some point. At this stage TD Thirteen would be less likely to make landfall north of South FL, given the strength of the ridge.

Excerpt from the latest NHC discussion suggests interaction with the Greater Antilles and/or (more probably) TD Fourteen are the only possible negatives:

The dynamical models suggests the centers will become more vertically aligned around 36-48 h and that the shear should diminish. However, the system could be close to Hispaniola during this time, and be near Cuba thereafter, especially if it moves south of the forecast track. The upper-level winds over the Gulf of Mexico should be generally favorable for development if the cyclone doesn't get too close to Tropical Depression Fourteen. The possibilities range from the system degenerating to an open wave as seen in the GFS and ECMWF to a major hurricane as seen in the HWRF.

It certainly possible to go on the right side of the current track, we are close enough to the point of closest approach to sofla and the fact that the NHC is still on the right side of guidance, it would be a major miss for the nhc at this range to have the system make landfall on manalnd sofla. The trend on the ridge is stronger and these systems don't bust through ridges...as good as conditions are down the road for 13, there is too much ridging in place for it to avoid disruption from land...if Im on the northern gulf coast, I buy gas and food today, nhc looks to conservative on intensity..mainland sofla, watch it but it appears to me its going south of key west and even if ti ramps up to a 2, we are in better shape than yesterday.

[Shell Mound]

It certainly possible to go on the right side of the current track, we are close enough to the point of closest approach to sofla and the fact that the NHC is still on the right side of guidance, it would be a major miss for the nhc at this range to have the system make landfall on mainland sofla...as good as conditions are down the road for 13, there is too much ridging in place for it to avoid disruption from land...watch it but it appears to me its going south of key west and even if it ramps up to a 2, we are in better shape than yesterday.

Current IR imagery indicates that the surface-based trough axis associated with TD Thirteen is clearly heading toward a convergent region with light shear between two TUTT axes, which would not only indicate much more conducive conditions for rapid organisation beginning in another day and a half, but also encourage a centre to either form farther north or rotate from SSE→NNW, following the initiation and expansion of convection on the northwestern side of the system. The NHC’s positions still take the system on a WNW course just to the north of the Greater Antilles, similar to the HWRF solution, which has been by far the best with the system in the short term, in terms of intensity, track, and (structural) evolution. So I think there is enough evidence that the system will miss the major land masses to the north and start to intensify rapidly once north of Puerto Rico, as the HWRF indicates. Since I think TD Fourteen will be much more intense than currently indicated in the same timeframe, I feel that TD Thirteen could “jog” more to the NW as it begins to rapidly deepen, before turning back to the WNW beneath strong ridging. Such a northward deviation near the extreme southeastern Bahamas before resuming a solid WNW heading would mean the difference between Key West and downtown Miami. As with TD Fourteen, I also think that even the HWRF may be too conservative with the intensity of TD Thirteen once it is fully stacked and ready to “bomb out.” Therefore, instead of a 120-knot system, say, hitting Key West, think of a 145-knot Category-5 hitting Coconut Grove, hypothetically.

[stormwatcher95]

Really trying to get it together this morning. Watching the low clouds it looks like a spin was pulled up under the northern mass and is starting to tighten up, to my untrained eye.

[jlauderdal]

Current IR imagery indicates that the surface-based trough axis associated with TD Thirteen is clearly heading toward a convergent region with light shear between two TUTT axes, which would not only indicate much more conducive conditions for rapid organisation beginning in another day and a half, but also encourage a centre to either form farther north or rotate from SSE→NNW, following the initiation and expansion of convection on the northwestern side of the system. The NHC’s positions still take the system on a WNW course just to the north of the Greater Antilles, similar to the HWRF solution, which has been by far the best with the system in the short term, in terms of intensity, track, and (structural) evolution. So I think there is enough evidence that the system will miss the major land masses to the north and start to intensify rapidly once north of Puerto Rico, as the HWRF indicates. Since I think TD Fourteen will be much more intense than currently indicated in the same timeframe, I feel that TD Thirteen could “jog” more to the NW as it begins to rapidly deepen, before turning back to the WNW beneath strong ridging. Such a northward deviation near the extreme southeastern Bahamas before resuming a solid WNW heading would mean the difference between Key West and downtown Miami. As with TD Fourteen, I also think that even the HWRF may be too conservative with the intensity of TD Thirteen once it is fully stacked and ready to “bomb out.” Therefore, instead of a 120-knot system, say, hitting Key West, think of a 145-knot Category-5 hitting Coconut Grove, hypothetically.

if it bombs out and its possible then a northward adjustment would be in the cards, at this point i don't see it getting that far north on to the mainland even at cat 5 which predicitn a cat 5 in itself is always a real stretch....your RI idea isn't crazy talk at all and your track into mainland south Florida is possible say 20% at this point IMO

[otowntiger]

Also no real strengthening expected for Next day or two. Looking like less and less threat for the FL peninsula east side. Keys are still going to need to be alert, but looks to stay even south of there, and not real strong at that.

The only reason the NHC is conservative is the possibility of interaction with the Greater Antilles, which in my view is less likely than a track just north of the islands, given that all the latest reliable guidance is tightly clustered near the Keys by days three and four, and the HWRF, along with the CMC, has consistently handled the short-term intensity trends and movement(s) better than the GFS/ECMWF, yet continues to indicate rapid deepening into a major hurricane commencing once TD Thirteen passes north of Puerto Rico and nears/enters the extreme southeastern Bahamas. The overall trends are definitely favouring a stronger ridge and a stronger TD Thirteen in three to five days that tracks farther west before turning north, so it is more likely to enter the eastern Gulf of Mexico before making its turn. The only question regards the placement of mesoscale features as well as the locations of both TD Thirteen and TD Fourteen in three to five days. No one in South Florida or the Keys should be dismissing this system; neither should anyone along the eastern Gulf Coast of the U.S., much less anyone in the Bahamas. Since both TD Thirteen and TD Fourteen may become powerful hurricanes at the time of their closest approaches to each other, TD Thirteen could certainly move a bit farther north than currently indicated before turning, that is, strike closer to Miami rather than Key West while moving WNW across the peninsula to the west coast of the state near, say, Tampa Bay. Currently, I think both depressions could be major hurricanes by days four and five, which is why I wouldn’t dismiss northward adjustments to the track of TD Thirteen through the Bahamas while en route to South FL. I think Miami/Fort Lauderdale is as much in play as the Keys at this point. The key is that both systems are going to make landfall in the U.S. at some point. At this stage TD Thirteen would be less likely to make landfall north of South FL, given the strength of the ridge. As I mentioned, this system has a good opportunity to affect either South FL or the Keys as a potentially powerful hurricane.

Excerpt from the latest NHC discussion suggests interaction with the Greater Antilles and/or (more probably) TD Fourteen are the only possible negatives:

The dynamical models suggests the centers will become more vertically aligned around 36-48 h and that the shear should diminish. However, the system could be close to Hispaniola during this time, and be near Cuba thereafter, especially if it moves south of the forecast track. The upper-level winds over the Gulf of Mexico should be generally favorable for development if the cyclone doesn't get too close to Tropical Depression Fourteen. The possibilities range from the system degenerating to an open wave as seen in the GFS and ECMWF to a major hurricane as seen in the HWRF.

Y’all are fast! I edited my original post taking out the part about it not being strong in the keys and staying to the south of there, but not fast enough to miss getting in your quote. Agreed things can still change of course but the NHC is very good on track this close in.

[Shell Mound]

Y’all are fast! I edited my original post taking out the part about it not being strong in the keys and staying to the south of there, but not fast enough to miss getting in your quote. Agreed things can still change of course but the NHC is very good on track this close in.

Miami and Fort Lauderdale are still in the cone, y’know. Regardless, I hope that everyone in the path is well prepared.

(I am currently in Europe, but my heart is in Florida, my native state. But as for my precise location, I wish to remain silent.)

[Weatherboy1]

Good morning! Just as I thought it might Yesterday evening, 13 seems to be getting its act together now. The whole “two centers, separated notably from each other” thing appears to be ending, with the SE convection/MLC dying off and NW Center/LLC taking charge. Will need some confirmation from the first visual satellite shots, but if this trend continues I wouldn’t be surprised to see this make TS status by 11 am

[Keldeo1997]

We might have a Tropical Storm

[jlauderdal]

Good morning! Just as I thought it might Yesterday evening, 13 seems to be getting its act together now. The whole “two centers, separated notably from each other” thing appears to be ending, with the SE convection/MLC dying off and NW Center/LLC taking charge. Will need some confirmation from the first visual satellite shots, but if this trend continues I wouldn’t be surprised to see this make TS status by 11 am

That wouldn't be good for florida

[Shell Mound]

The only negative factor in the short term is the rapid forward motion. If anything, some interaction with land to the south could aid organisation:
 https://twitter.com/OSUWXGUY/status/1296765520042229761



 https://twitter.com/ToddKimberlain/status/1296582183189123072



 https://twitter.com/_jwall/status/1296766864975175681

[northjaxpro]

Great early morning discussion and analysis Shell Mound, and Jlauderdal.