ATL: ISAAC - Post-Tropical - Discussion

[Weatherboy1]

WeatherOrKnot - My take is that we're still about 6 days out on this thing, give or take 12-18 hours either way. So it's tough to say if this rides the west coast, rides the east coast, goes right up the spine of the peninsula or misses us entirely to the east or west. I think by Thursday morning we'll have a much better idea for the potential impact here in SE FL.

It really comes down to "angle of attack" too. Late season storms a la Wilma tend to be in the process of getting caught up by deeper troughs. In that case, they are generally moving SW to NE. So even a storm that hits in SW FL could have significant impact on the east coast. But we're still in August, and this system is likely just going to gradually turn into any weakness in the ridge north of it rather than get yanked up by a deep trough and hurled NE. So for us to get the worst of brunt of anything, the turn would have to take place sooner than what the latest euro and GFS are showing. We'd still get nasty weather, of course, but not the core of the storm.

But again, this is all six days out and it's really too soon to say. Hope this helps anyway!

Just my opinon ... and no I am not an expert!

[ndale]

If there is storm in Florida next week, the news service should pick this story up right away since there is a political convention there next week.

[CourierPR]

Tropicwatch, I think the key words in your post are "current steering." Apparently things are forecast to change in the coming days.

[Aric Dunn]

center is full exposed again. convection collapsing. the ne shear is still helping to transport the dry air on the system. probably wont strengthen much till that happens.

[tolakram]

center is full exposed again. convection collapsing. the ne shear is still helping to transport the dry air on the system. probably wont strengthen much till that happens.

Yes, but unlike previous storms the center is exposed on the east side of the convection, and some convection still firing. Different conditions for sure.

saved loop

[CourierPR]

WeatherOrKnot - My take is that we're still about 6 days out on this thing, give or take 12-18 hours either way. So it's tough to say if this rides the west coast, rides the east coast, goes right up the spine of the peninsula or misses us entirely to the east or west. I think by Thursday morning we'll have a much better idea for the potential impact here in SE FL.

It really comes down to "angle of attack" too. Late season storms a la Wilma tend to be in the process of getting caught up by deeper troughs. In that case, they are generally moving SW to NE. So even a storm that hits in SW FL could have significant impact on the east coast. But we're still in August, and this system is likely just going to gradually turn into any weakness in the ridge north of it rather than get yanked up by a deep trough and hurled NE. So for us to get the worst of brunt of anything, the turn would have to take place sooner than what the latest euro and GFS are showing. We'd still get nasty weather, of course, but not the core of the storm.

But again, this is all six days out and it's really too soon to say. Hope this helps anyway!

In 1964, Cleo made a fairly sharp northerly turn in late August. What weather, if any, Southeast Florida would experience would probably depend on the size and strength of the storm, and how soon it begins to recurve.

[tolakram]

Closeup, 16:15z, one new tower.

[Wthrman13]

One final thing: technically, moisture content has nothing to do with the "cap" per se, although in general a capping inversion is drier than the layers above and below it. The dry air doesn't cap the rising convection as much as dilute it, robbing it of it's buoyancy and thus, upward acceleration. This happens throughout the depth of the troposphere, however, whenever the surroundings of the rising cumulus are subsaturated (which is nearly always the case). The drier the air, the more the dilution of the thunderstorm updraft, and the weaker the updrafts become, which is why dry air is so detrimental to developing TC's.


So if the air around the updraft is a wet sponge the acc.continues hence the surrounding enviroment is already saturated?is that correct?

If I'm understanding you correctly, yes. If the environmental air surrounding a deep convective updraft is relatively moist, then, when that air is entrained into the sides of the updraft (remember, the updraft is cloudy, so it is saturated, even supersaturated), it won't dilute the moisture content of the updraft as much as if the air were very dry.

[ROCK]

NE shear Aric and the fact is still trucking along at a good clip.....LLC exposed and popped out above 15N now....

[Javlin]

One final thing: technically, moisture content has nothing to do with the "cap" per se, although in general a capping inversion is drier than the layers above and below it. The dry air doesn't cap the rising convection as much as dilute it, robbing it of it's buoyancy and thus, upward acceleration. This happens throughout the depth of the troposphere, however, whenever the surroundings of the rising cumulus are subsaturated (which is nearly always the case). The drier the air, the more the dilution of the thunderstorm updraft, and the weaker the updrafts become, which is why dry air is so detrimental to developing TC's.


So if the air around the updraft is a wet sponge the acc.continues hence the surrounding enviroment is already saturated?is that correct?

If I'm understanding you correctly, yes. If the environmental air surrounding a deep convective updraft is relatively moist, then, when that air is entrained into the sides of the updraft (remember, the updraft is cloudy, so it is saturated, even supersaturated), it won't dilute the moisture content of the updraft as much as if the air were very dry.

Yes that was my thinking that the updraft stays moist=weight which in turn adds force for acceleration?to make the punch.

[ROCK]

vort looks good...and low level convergence has increased..

http://tropic.ssec.wisc.edu/real-time/w ... oom=&time=

[hurricanes1234]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

The circulation is exposed again. Won't be surprised if the depression is weaker by the next advisory. I would love to see this one become a major hurricane, but considering the path it's taking, not too much anymore. I would prefer the 60% wave in the Atlantic to become major. Also, the predicted path would take it through the Caribbean, possibly bringing torrential rainfall to islands already affected by Ernesto and Helene, including the T&T islands, in which some of us are still providing clean up/relief efforts for the flooding caused by Helene when it passed through the island chain as a remnant tropical wave. But don't worry though, most streets/roads/houses have been cleared of the thick mud that came with the floods.

[Bocadude85]

center is full exposed again. convection collapsing. the ne shear is still helping to transport the dry air on the system. probably wont strengthen much till that happens.

Yea I was thinking the NHC may be a little overzealous on their intensity forecast.... just my opinion of course.

[ozonepete]

Yes that was my thinking that the updraft stays moist=weight which in turn adds force for acceleration?to make the punch.

Don't understand the "moist=weight" thing. Water vapor is lighter than air molecules. Moist warm air is less dense, not more dense.

[Aric Dunn]

center is full exposed again. convection collapsing. the ne shear is still helping to transport the dry air on the system. probably wont strengthen much till that happens.

Yea I was thinking the NHC may be a little overzealous on their intensity forecast.... just my opinion of course.

no I think they are right on. in the next 12 to 24 hours the ne shear will lower and it should be able to maintain convection by which time it should begin to slow down some as well.

[ConvergenceZone]

NE shear Aric and the fact is still trucking along at a good clip.....LLC exposed and popped out above 15N now....

Rock, when you say, "the LLC is exposed and popped out" does that mean
that the depression has opened to a wave?

[ROCK]

NE shear Aric and the fact is still trucking along at a good clip.....LLC exposed and popped out above 15N now....

Rock, when you say, "the LLC is exposed and popped out" does that mean
that the depression has opened to a wave?

no...not going to open up to a wave...

[robbielyn]

no just means its not under the convection

[Frank2]

Not convection-free but more convection-free swirl than anything else at this time - perhaps in a day or two things will change once it slows down, and that's the problem with the public hearing or reading only advisories - they leave the imagination to think this is a much more than it is right now...

[psyclone]

Yes that was my thinking that the updraft stays moist=weight which in turn adds force for acceleration?to make the punch.

Don't understand the "moist=weight" thing. Water vapor is lighter than air molecules. Moist warm air is less dense, not more dense.

absolutely. witness the lifting mechanism on the high plains of the "dry line" for convective initiation. dry air is much heavier than moisture laden air.