ATL: FRANCINE - Remnants - Discussion

[cycloneye]

AL, 91, 2024090712, , BEST, 0, 188N, 927W, 20, 1005, DB

https://ftp.nhc.noaa.gov/atcf/btk/bal912024.dat

[Hurricane2022]

After 13 days and 54 pages... finally here we are.

[tropicwatch]

AL, 91, 2024090712, , BEST, 0, 188N, 927W, 20, 1005, DB

https://ftp.nhc.noaa.gov/atcf/btk/bal912024.dat

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

Pressures are decently low in that area.

[wx98]

Looks like the GFS makes a hurricane out of it of course…

[Sciencerocks]

[Teban54]

Dear time-traveler looking at this thread from the future,

You're looking at one of the most puzzling moments in the recorded history of Atlantic hurricane activities. Every professional forecast agency expected a hyperactive 2024 season, fueled by record-breaking SSTs and OHCs in the tropics, aggressive climate models, and Hurricane Beryl, the earliest Cat 4 and Cat 5 on record.

Yet, the Atlantic went into complete silence after Ernesto became post-tropical on August 20. Very few years in the satellite era had no active storms between August 20 and September 6, and 2024 is one of them. Not just that, but as of writing, the 60% 7-day formation chance of this system (91L) is the highest we've seen in the entire basin over this period. There had only been one other orange AOI, though there were 5 lemons at once day ago.

The worst part is that we can't even figure out why. There are several theories put up by experts and weather nerds alike, but nothing conclusive at the moment. ITCZ being too far north? African Easterly Jet being too strong? Tropopause being too warm? +NAO possibly related to dry air being dumped from higher latitudes? Sunspot activity? Unfortunate MJO timing? Or just sheer bad luck?

This invest, 91L, is emblematic of the entire season's struggles during this period. Its pre-invest thread ended at 54 pages and 1076 posts, one of the longest on Storm2K if not the single longest. At various points, model expectations for this system were wildly different: a hurricane in the MDR that recurves north of the Caribbean islands; an Ida-like storm that bombs out in the Gulf; a wave crossing over to EPAC where it develops; a merger into 90L which was expected to be the more dominant system; and of course, no development at all at various points in-between. Consequently, NHC's development chances went through wild ups and downs, from 10/50 to 0/20 and now back to 30/60. Just less than 48 hours ago, it looked certain that this wave wouldn't develop.

Perhaps you're here to see the first storm after one of the most unexpected and intriguing lulls in history. Perhaps you heard of this system having the longest pre-invest thread on S2K. Or perhaps nothing comes out of this -- which would totally be unsurprising given the system's history -- and this thread is forgotten over time.

Either way, I hope that those of you reading this now have a much better idea of what happened to 2024 than we do in real time. Did the season go full-on 2013 after mid-August? Did it become one of the most back-loaded seasons in history, especially among hyperactive ACE seasons? Or was it an "it only takes one" season, where a single bad Sep/Oct major hurricane caught everyone off guard? And did 91L mark the start of the switch flip, or was it just an anomaly in an otherwise quiet period? We have no way to know, but you do. Hopefully this thread will be less of a head-scratcher for you, and that forecasters and weather fans in your era have learned something about seasonal forecasting and/or effects of global warming that will help with future predictions.

[3090]

Dear time-traveler looking at this thread from the future,

You're looking at one of the most puzzling moments in the recorded history of Atlantic hurricane activities. Every professional forecast agency expected a hyperactive 2024 season, fueled by record-breaking SSTs and OHCs in the tropics, aggressive climate models, and Hurricane Beryl, the earliest Cat 4 and Cat 5 on record.

Yet, the Atlantic went into complete silence after Ernesto became post-tropical on August 20. Very few years in the satellite era had no active storms between August 20 and September 6, and 2024 is one of them. Not just that, but as of writing, the 60% 7-day formation chance of this system (91L) is the highest we've seen in the entire basin over this period. There had only been one other orange AOI, though there were 5 lemons at once day ago.

The worst part is that we can't even figure out why. There are several theories put up by experts and weather nerds alike, but nothing conclusive at the moment. ITCZ being too far north? African Easterly Jet being too strong? Tropopause being too warm? +NAO possibly related to dry air being dumped from higher latitudes? Sunspot activity? Unfortunate MJO timing? Or just sheer bad luck?

This invest, 91L, is emblematic of the entire season's struggles during this period. Its pre-invest thread ended at 54 pages and 1076 posts, one of the longest on Storm2K if not the single longest. At various points, model expectations for this system were wildly different: a hurricane in the MDR that recurves north of the Caribbean islands; an Ida-like storm that bombs out in the Gulf; a wave crossing over to EPAC where it develops; a merger into 90L which was expected to be the more dominant system; and of course, no development at all at various points in-between. Consequently, NHC's development chances went through wild ups and downs, from 10/50 to 0/20 and now back to 30/60. Just less than 48 hours ago, it looked certain that this wave wouldn't develop.

Perhaps you're here to see the first storm after one of the most unexpected and intriguing lulls in history. Perhaps you heard of this system having the longest pre-invest thread on S2K. Or perhaps nothing comes out of this -- which would totally be unsurprising given the system's history -- and this thread is forgotten over time.

Either way, I hope that those of you reading this now have a much better idea of what happened to 2024 than we do in real time. Did the season go full-on 2013 after mid-August? Did it become one of the most back-loaded seasons in history, especially among hyperactive ACE seasons? Or was it an "it only takes one" season, where a single bad Sep/Oct major hurricane caught everyone off guard? And did 91L mark the start of the switch flip, or was it just an anomaly in an otherwise quiet period? We have no way to know, but you do. Hopefully this thread will be less of a head-scratcher for you, and that forecasters and weather fans in your era have learned something about seasonal forecasting and/or effects of global warming that will help with future predictions.

I fell asleep halfway thru reading this. I’ll need to return at some point in the “future”, to finish reading same.

[Frank P]

Latest vis sat loops up close and personal. Be interesting to see how it develops once that circulation gets entirely over water, looks like half of it is still over land.

[ElectricStorm]

I'm thinking this finally becomes Francine. Probably a low-mid TS at peak unless it somehow blows up more than expected

[WaveBreaking]

I'm thinking this finally becomes Francine. Probably a low-mid TS at peak unless it somehow blows up more than expected

The only way I could see this blowing up unexpectedly is if 91L gets a decent structure before it runs into the front and gets sheared. The BOC does have a history of helping disturbances curl up faster than expected (i.e., Alberto and Chris from this year), so maybe if 91L completes the merger favorably and also gets a favorable jet interaction then yeah it could do something. But I’m not hanging my hat on this outcome since it relies on a lot of things going right for this system. And given how this wave has had a hard time getting itself together up until now, I don’t see this happening.

[cheezyWXguy]

12z gfs peaks this at 978mb. A few of the earlier gefs members got it sub-980 as well. TS is probably most likely at this point, but there seems to be potential for higher if things play out the right way

[TomballEd]

91L doesn't have great shear before it reaches 25N, but the screaming shear is N of it and will put 91L is an upward motion region. After passing the latitude of the Rio Grande, it gets into higher shear, but proximity to the entrance region of the jet to its NW is enough to counter the increasing shear and the GFS continues to strengthen as it heads towards WxMan57 TX/LA border region. Dry mid level air is wrapping in, but hasn't quite reached the center at landfall. GFS 978 mb pressure in the NW Gulf, if it verifies, should get the system to hurricane strength.

That was a long AOI thread, from my concern does it develop too early and go out to sea, to whether it forms in the Caribbean and is a hurricane in the Gulf, to decreasing odds, model support and satellite products deteriorating, back to zombie status, life after death.

GEFS are fairly tightly clustered, although the shape of the Mexico-Texas coastline produces a spread of landfall points, it does look like W. Louisiana is the preferred ensemble prediction at this point in time.

[TomballEd]

I'm thinking this finally becomes Francine. Probably a low-mid TS at peak unless it somehow blows up more than expected

The only way I could see this blowing up unexpectedly is if 91L gets a decent structure before it runs into the front and gets sheared. The BOC does have a history of helping disturbances curl up faster than expected (i.e., Alberto and Chris from this year), so maybe if 91L completes the merger favorably and also gets a favorable jet interaction then yeah it could do something. But I’m not hanging my hat on this outcome since it relies on a lot of things going right for this system. And given how this wave has had a hard time getting itself together up until now, I don’t see this happening.

See above, GFS is suggesting favorable interaction with the jet over Texas, aka baroclinic enhancement. Hurricane force is not impossible.

[wx98]

I'm thinking this finally becomes Francine. Probably a low-mid TS at peak unless it somehow blows up more than expected

The only way I could see this blowing up unexpectedly is if 91L gets a decent structure before it runs into the front and gets sheared. The BOC does have a history of helping disturbances curl up faster than expected (i.e., Alberto and Chris from this year), so maybe if 91L completes the merger favorably and also gets a favorable jet interaction then yeah it could do something. But I’m not hanging my hat on this outcome since it relies on a lot of things going right for this system. And given how this wave has had a hard time getting itself together up until now, I don’t see this happening.

See above, GFS is suggesting favorable interaction with the jet over Texas, aka baroclinic enhancement. Hurricane force is not impossible.

I agree. These are the type of systems that can surprise you pretty quickly. We will see.

[3090]

The only way I could see this blowing up unexpectedly is if 91L gets a decent structure before it runs into the front and gets sheared. The BOC does have a history of helping disturbances curl up faster than expected (i.e., Alberto and Chris from this year), so maybe if 91L completes the merger favorably and also gets a favorable jet interaction then yeah it could do something. But I’m not hanging my hat on this outcome since it relies on a lot of things going right for this system. And given how this wave has had a hard time getting itself together up until now, I don’t see this happening.

See above, GFS is suggesting favorable interaction with the jet over Texas, aka baroclinic enhancement. Hurricane force is not impossible.

I agree. These are the type of systems that can surprise you pretty quickly. We will see.

Exactly what happened with Zeta and thus, it reached CAT 3 status unexpectedly.

[cheezyWXguy]

See above, GFS is suggesting favorable interaction with the jet over Texas, aka baroclinic enhancement. Hurricane force is not impossible.

I agree. These are the type of systems that can surprise you pretty quickly. We will see.

Exactly what happened with Zeta and thus, it reached CAT 3 status unexpectedly.

Speaking of Zeta, and Ian for that matter (exclusively on trough interaction, not intensity): is this another one of those setups where trough interaction results in an enhanced northwest side of the storm? If so, this would raise the impacts to coastal areas that this system comes close enough to affect.

[TomballEd]

I agree. These are the type of systems that can surprise you pretty quickly. We will see.

Exactly what happened with Zeta and thus, it reached CAT 3 status unexpectedly.

Speaking of Zeta, and Ian for that matter (exclusively on trough interaction, not intensity): is this another one of those setups where trough interaction results in an enhanced northwest side of the storm? If so, this would raise the impacts to coastal areas that this system comes close enough to affect.

GFS has the storm in the right entrance of a 200 mb jet over Texas

[WaveBreaking]

Exactly what happened with Zeta and thus, it reached CAT 3 status unexpectedly.

Speaking of Zeta, and Ian for that matter (exclusively on trough interaction, not intensity): is this another one of those setups where trough interaction results in an enhanced northwest side of the storm? If so, this would raise the impacts to coastal areas that this system comes close enough to affect.

GFS has the storm in the right entrance of a 200 mb jet over Texas

Yeah now that I think of it, things could quickly go south if 91L manages to take advantage of the approaching trough that the gfs shows and the swath of 30°C waters in its path. It’s a good thing that 90L helped to cool the NGOM waters a little by meandering over them for almost a week.

[cycloneye]

Code Red

Western Gulf of Mexico (AL91):
An area of low pressure has formed over the Bay of Campeche and is
producing disorganized showers and thunderstorms. The system is
forecast to drift slowly northward for a couple of days while it
interacts with a frontal boundary. Environmental conditions are
forecast to be conducive for development, and a tropical depression
is likely to form during the early or middle part of next week while
the system moves generally northward near or along the Mexican and
Texas Gulf coastline. Interests along the western Gulf of Mexico
coast should closely monitor the progress of this system.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 7 days...high...70 percent.

[Teban54]

Code Red

Western Gulf of Mexico (AL91):
An area of low pressure has formed over the Bay of Campeche and is
producing disorganized showers and thunderstorms. The system is
forecast to drift slowly northward for a couple of days while it
interacts with a frontal boundary. Environmental conditions are
forecast to be conducive for development, and a tropical depression
is likely to form during the early or middle part of next week while
the system moves generally northward near or along the Mexican and
Texas Gulf coastline. Interests along the western Gulf of Mexico
coast should closely monitor the progress of this system.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 7 days...high...70 percent.

This is the first cherry since August 12 (when the last cherry became Ernesto).