ATL: DEBBY - Post-Tropical

[Air Force Met]

I think this storm is going to surprise everyone at how fast it turns into a major hurricane. Look at the moisture stream behind it from the Pacific and southern Caribbean, it's sitting over the Loop current right now--the hottest water in the Atlantic basin, and its strong shear is starting to convert into a very favorable upper level environment. Be prepared to be surprised when you wake up tomorrow morning at its impressiveness.

I'll be prepared to not hold my breath...

AFM- long time since I seen you around. Welcome back...

Thanks.

And tops are starting to warm...just in time for the diurnal min. Shear is certainly not relaxing. You can see the deformation zone running from the NW coast of the Yucatan to about 24N/87/88W. That's the battle zone b/w the outflow and the shear...and the shear is winning.

As I said earlier...this convective blow up was due mainly to convergence on the east side of the low and the inflow...but not the low reforming. Now that convection is waning...it will have to wait until later.

[vaffie]

buoy 42056 just reported a 33 knot 1 minute-sustained wind, winds continuing to pick up. If the past 24 hours trend were just to continue through tomorrow morning, never mind speed up, it will have a pressure of about 1001 mb and winds of about 50 mph.

[Air Force Met]

buoy 42056 just reported a 33 knot 1 minute-sustained wind, winds continuing to pick up. If the past 24 hours trend were just to continue through tomorrow morning, never mind speed up, it will have a pressure of about 1001 mb and winds of about 50 mph.

Pressure gradient will do that to you...but it still doesn't change the fact that cloud tops are warming before the low got a chance to tuck. Convection, in these broad lows, goes in spurts...in cycles. Now that it has exploded...it will be a long while before it recharges...perhaps later this evening...or maybe tomorrow morning. It is the thermodynamic process of latent heat release that will move the low pressure under the convection and get the ball rolling.

Until that happens...we are in another holding pattern. And this is what happens with these systems. We've seen it a thousand times. We get two steps forward and 1 step back. They inch their way towards development until finally a well defined LLC gets tucked under SUSTAINED convection.

AND THEN...in cases like this...what usually happens is the shear knocks the crap out of it and it gets exposed again.

[Dean4Storms]

I don't see this organizing all that fast, circulation is very broad and most of it devoid of any deep convection.

[vaffie]

I don't see this organizing all that fast, circulation is very broad and most of it devoid of any deep convection.

Haha, that's why I said you'll all be surprised, because no one is seeing it happening fast. Anyway, I'll be back in a couple hours, have to take care of stuff.

[SoupBone]

buoy 42056 just reported a 33 knot 1 minute-sustained wind, winds continuing to pick up. If the past 24 hours trend were just to continue through tomorrow morning, never mind speed up, it will have a pressure of about 1001 mb and winds of about 50 mph.

Pressure gradient will do that to you...but it still doesn't change the fact that cloud tops are warming before the low got a chance to tuck. Convection, in these broad lows, goes in spurts...in cycles. Now that it has exploded...it will be a long while before it recharges...perhaps later this evening...or maybe tomorrow morning. It is the thermodynamic process of latent heat release that will move the low pressure under the convection and get the ball rolling.

Until that happens...we are in another holding pattern. And this is what happens with these systems. We've seen it a thousand times. We get two steps forward and 1 step back. They inch their way towards development until finally a well defined LLC gets tucked under SUSTAINED convection.

AND THEN...in cases like this...what usually happens is the shear knocks the crap out of it and it gets exposed again.

I'm enjoying this discussion. Thanks for typing it at an intermediate level so that it is easier to understand. I'm curious to know what, if any, dry air intrusion this low is experiencing. Does anyone have an illustration depicting this?

[Flakeys]

sfwmd site

http://www.sfwmd.gov/portal/page/portal/xweb%20weather/hurricane%20model%20plots

[Air Force Met]

I'm enjoying this discussion. Thanks for typing it at an intermediate level so that it is easier to understand. I'm curious to know what, if any, dry air intrusion this low is experiencing. Does anyone have an illustration depicting this?

There is some dry air showing up in the WV imagery...but it is because of subsidence from the shear colliding with the outflow. They hit and have no place to go but down...which means the air warms and dries.

[Aric Dunn]

buoy 42056 just reported a 33 knot 1 minute-sustained wind, winds continuing to pick up. If the past 24 hours trend were just to continue through tomorrow morning, never mind speed up, it will have a pressure of about 1001 mb and winds of about 50 mph.

Pressure gradient will do that to you...but it still doesn't change the fact that cloud tops are warming before the low got a chance to tuck. Convection, in these broad lows, goes in spurts...in cycles. Now that it has exploded...it will be a long while before it recharges...perhaps later this evening...or maybe tomorrow morning. It is the thermodynamic process of latent heat release that will move the low pressure under the convection and get the ball rolling.

Until that happens...we are in another holding pattern. And this is what happens with these systems. We've seen it a thousand times. We get two steps forward and 1 step back. They inch their way towards development until finally a well defined LLC gets tucked under SUSTAINED convection.

AND THEN...in cases like this...what usually happens is the shear knocks the crap out of it and it gets exposed again.

yep, got to warm the atmosphere suffeciently. Still believe the dynamics are in place for something to eventually get going on the eastern side of the broad low. once convection can maintain long enough.

[thetruesms]

Pressure gradient will do that to you...but it still doesn't change the fact that cloud tops are warming before the low got a chance to tuck. Convection, in these broad lows, goes in spurts...in cycles. Now that it has exploded...it will be a long while before it recharges...perhaps later this evening...or maybe tomorrow morning. It is the thermodynamic process of latent heat release that will move the low pressure under the convection and get the ball rolling.

Until that happens...we are in another holding pattern. And this is what happens with these systems. We've seen it a thousand times. We get two steps forward and 1 step back. They inch their way towards development until finally a well defined LLC gets tucked under SUSTAINED convection.

AND THEN...in cases like this...what usually happens is the shear knocks the crap out of it and it gets exposed again.

I'm reading through the post, nodding approvingly, going "yup, yup - well written explanation". Then I get to the last line, and it just kills me. It's funny because it's true.

[robbielyn]

buoy 42056 just reported a 33 knot 1 minute-sustained wind, winds continuing to pick up. If the past 24 hours trend were just to continue through tomorrow morning, never mind speed up, it will have a pressure of about 1001 mb and winds of about 50 mph.

Pressure gradient will do that to you...but it still doesn't change the fact that cloud tops are warming before the low got a chance to tuck. Convection, in these broad lows, goes in spurts...in cycles. Now that it has exploded...it will be a long while before it recharges...perhaps later this evening...or maybe tomorrow morning. It is the thermodynamic process of latent heat release that will move the low pressure under the convection and get the ball rolling.

Until that happens...we are in another holding pattern. And this is what happens with these systems. We've seen it a thousand times. We get two steps forward and 1 step back. They inch their way towards development until finally a well defined LLC gets tucked under SUSTAINED convection.

AND THEN...in cases like this...what usually happens is the shear knocks the crap out of it and it gets exposed again.

I'm enjoying this discussion. Thanks for typing it at an intermediate level so that it is easier to understand. I'm curious to know what, if any, dry air intrusion this low is experiencing. Does anyone have an illustration depicting this?

Jeff masters said there is dry air hampering development in the central gulf. He also said moderate shear will allow for slow development through Saturday night then shear will increase again. So this has alot going against it becoming too strong

[Air Force Met]

Jeff masters said there is dry air hampering development in the central gulf. He also said moderate shear will allow for slow development through Saturday night then shear will increase again. So this has alot going against it becoming too strong

And I agree. This thing will never be free of the shear once it moves north of 25. When I sent out my update yesterday to the State I mentioned this very reason for not buying into the Euro/CMC solution on strength. It always looks to me like it will be battling 10-20 kts of shear. Nothing that will kill it...but enough to keep a lid on it.

[otowntiger]

I am good with this thing not developing any time soon, if ever. I'm happy with the rain it may/may not bring us. I do hope for some good soaking rains all across the state.

[TropicalAnalystwx13]

The GFS Ensemble Mean/ECMWF shows that wind shear will not be a problem for 96L. There is an anticyclone located in the Gulf that should eventually become stacked with the system and provide a low shear environment for the next several days. If 96L goes east, I could see it being a problem close to landfall, but if it goes west, it shouldn't be a problem.

[adam0983]

There is just way too much shear this time of year in the Gulf of Mexico for Invest 96L to strengthen into a major storm.

[petit_bois]

There is just way too much shear this time of year in the Gulf of Mexico for Invest 96L to strengthen into a major storm.

never say never... but I hope you are right with this one.

[robbielyn]

Latest gfs stubbornly sending it toward big bend of fl. I'm calling all the people I know to blow it westward. I got beach plans timing is not good.

[ROCK]

12Z NOGAPS in 24hrs....

https://www.fnmoc.navy.mil/wxmap_cgi/cg ... t=Tropical


just a big blob..... at 36hrs

[ROCK]

12Z NAM loop.....

http://mag.ncep.noaa.gov/NCOMAGWEB/appc ... mageSize=M

[chaser1]

Jeff masters said there is dry air hampering development in the central gulf. He also said moderate shear will allow for slow development through Saturday night then shear will increase again. So this has alot going against it becoming too strong

And I agree. This thing will never be free of the shear once it moves north of 25. When I sent out my update yesterday to the State I mentioned this very reason for not buying into the Euro/CMC solution on strength. It always looks to me like it will be battling 10-20 kts of shear. Nothing that will kill it...but enough to keep a lid on it.

I think it is for these reasons ( shear and dry air ), that I cannot see how this system can develop unless if it were to take advantage of the moderately better conditions near or just east of Yucatan. Now that the present convective bursting has stopped and without any further evidence that a low level center is trying to establish itself there, I would tend to think that NHC would likely back off the forecasted % for 48 hr. development a tad. At this point am less inclined to believe a depression may form by late Sunday than I was 12 hours ago.