ATL: GABRIELLE - Remnants - Discussion

[USTropics]

While convection is waning as can be expected with this time of day, I'm noticing improving outflow to the south of the system.

When is the Diurnal Maximum and Diurnal Minimum? I'm fairly new to this.

Here's a more technical response of the mechanisms at play with DMIN and DMAX that I wrote a few months ago.

The earth's crust has a high heat capacity, allowing it to absorb solar radiation throughout the day. Through conduction, the earths crust begins to heat up the air directly above it, which heats up the cool air column directly above that. While the sun is at its highest point at noon (and thus solar radiation at its most concentrated strength), maximum solar heat lags behind by several hours, as the ground and air layer must first absorb heat before it can begin to radiate heat. When the amount of incoming solar radiation equals the amount of outgoing radiation (around 3-5pm), we reach our daily high temperature.

CAPE (Convective Available Potential Energy) is at a maximum during the day due to this daytime heating, which is why we see a convective maximum late in the afternoon over land (afternoon thunderstorms you can set your clock to in Florida). However, this mechanism has no inherent effect on tropical convection.

There is another mechanism in play that aides in tropical moisture though. During the overnight and early morning hours, the earth is no longer absorbing solar radiation, and is therefore radiating heat back to space at its maximum potential, which is why temperatures decrease overnight. The warm surface continues to mix convectively upward at night, being replaced by cooler air towards the surface. This creates a more moist atmospheric profile, and given sufficient forcing for rising motion (in the tropics, converging winds at the low levels such as those associated with the ITCZ or a tropical wave/cyclone), convection is most likely to be at its maximum just before the sun rises in the tropics.

This post is NOT AN OFFICIAL FORECAST and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org. For Official Information please refer to the NHC and NWS products.

[Cyclenall]

000
ABNT20 KNHC 011748
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SUN SEP 1 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A WELL-DEFINED LOW PRESSURE SYSTEM IS LOCATED ABOUT 100 MILES EAST
OF THE CENTRAL LESSER ANTILLES. SATELLITE IMAGERY INDICATES THAT
THE ASSOCIATED THUNDERSTORM ACTIVITY HAS INCREASED AND IS SHOWING
SIGNS OF ORGANIZATION. UPPER-LEVEL WINDS ARE QUITE CONDUCIVE...
BUT PROXIMITY TO DRY AIR IN THE MIDDLE- AND UPPER-LEVELS OF THE
ATMOSPHERE COULD INHIBIT DEVELOPMENT OF THIS DISTURBANCE. THIS
SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS...AND A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 5 DAYS
WHILE IT MOVES WESTWARD AT 10 TO 15 MPH ACROSS THE CARIBBEAN SEA.
REGARDLESS OF WHETHER OR NOT A TROPICAL CYCLONE FORMS...LOCALLY
HEAVY RAINFALL AND STRONG GUSTY WINDS ARE EXPECTED TO AFFECT
PORTIONS OF THE LESSER ANTILLES TODAY THROUGH MONDAY.

FORECASTER STEWART

This was a unique TWO from the NHC, I don't recall wording like that before such as quite favorable shear and then the talk of the different levels of dry air. They must be getting bored so using different and more advanced analysis here makes sense.

Still don't see much substantial inflow at low levels with 97L.Wouldn't be surprised if all convection poofs. IR imagery at the moment is certainly not one of a developing TC in my opinion.

In 2013 systems cant hold convection for more then 2hrs it seems.

That's what I'm expecting. Its looks like its in a perfect position and whatnot to become a very interesting system but I'm not being fooled here; the motto remains true: if its too good to be true, its too good to be true. Its because Invest 97L exists during this year and not one like 2010 or 2008.

Whaddya mean? Has plenty of convection with it. Looks like a developing TC to me.

It may appear to be forming into something from the perspective of someone who isn't fully experienced in tropical cyclogenesis over many years or a few. During my first year of tracking the tropics closely this type of system would excite me as well but when you closely watch the motion of the convection it appears to be erratic and not consolidating. The convection is rapidly forming and waning so it could all collapse at any moment. While its possible it could be slowly forming, its unlikely to be well defined. I will admit you got closer than I thought to the TWO % at 2:00 pm today and it is doing better than I thought it would now but I think after 36 hours the "honeymoon" will be over .

[tolakram]

Live IR loop: http://wwwghcc.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=15&lon=-61&info=ir&zoom=2&width=1000&height=800&type=Animation&quality=95&palette=ir2.pal&numframes=5

[SouthDadeFish]

Not very impressive on microwave...

[SFLcane]

No TC developing anytime soon..

[ninel conde]

Not very impressive on microwave...

i definitely think the eastern convection will die. IF, and thats a big if, anything ever develops it will be from the western convection.

[HurricaneDREW92]

A blind squirrel eventually finds a nut

000
ABNT20 KNHC 011748
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SUN SEP 1 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A WELL-DEFINED LOW PRESSURE SYSTEM IS LOCATED ABOUT 100 MILES EAST
OF THE CENTRAL LESSER ANTILLES. SATELLITE IMAGERY INDICATES THAT
THE ASSOCIATED THUNDERSTORM ACTIVITY HAS INCREASED AND IS SHOWING
SIGNS OF ORGANIZATION. UPPER-LEVEL WINDS ARE QUITE CONDUCIVE...
BUT PROXIMITY TO DRY AIR IN THE MIDDLE- AND UPPER-LEVELS OF THE
ATMOSPHERE COULD INHIBIT DEVELOPMENT OF THIS DISTURBANCE. THIS
SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS...AND A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 5 DAYS
WHILE IT MOVES WESTWARD AT 10 TO 15 MPH ACROSS THE CARIBBEAN SEA.
REGARDLESS OF WHETHER OR NOT A TROPICAL CYCLONE FORMS...LOCALLY
HEAVY RAINFALL AND STRONG GUSTY WINDS ARE EXPECTED TO AFFECT
PORTIONS OF THE LESSER ANTILLES TODAY THROUGH MONDAY.

FORECASTER STEWART

This was a unique TWO from the NHC, I don't recall wording like that before such as quite favorable shear and then the talk of the different levels of dry air. They must be getting bored so using different and more advanced analysis here makes sense.

Still don't see much substantial inflow at low levels with 97L.Wouldn't be surprised if all convection poofs. IR imagery at the moment is certainly not one of a developing TC in my opinion.

In 2013 systems cant hold convection for more then 2hrs it seems.

That's what I'm expecting. Its looks like its in a perfect position and whatnot to become a very interesting system but I'm not being fooled here; the motto remains true: if its too good to be true, its too good to be true. Its because Invest 97L exists during this year and not one like 2010 or 2008.

Whaddya mean? Has plenty of convection with it. Looks like a developing TC to me.

It may appear to be forming into something from the perspective of someone who isn't fully experienced in tropical cyclogenesis over many years or a few. During my first year of tracking the tropics closely this type of system would excite me as well but when you closely watch the motion of the convection it appears to be erratic and not consolidating. The convection is rapidly forming and waning so it could all collapse at any moment. While its possible it could be slowly forming, its unlikely to be well defined. I will admit you got closer than I thought to the TWO % at 2:00 pm today and it is doing better than I thought it would now but I think after 36 hours the "honeymoon" will be over .

[psyclone]

I agree with the "no fast development" crowd and will mention one of my favorite activities to keep things in perspective: invert the NHC development probs to create non development probs (ie a 40% chance of development within a given timeframe also = a 60% chance of no development during said timeframe). that'll help maintain a pragmatic balance especially when enthusiasm begins to bubble over.

[USTropics]

low-level vorticity building to the west now:

[SFLcane]

low-level vorticity building to the west now:

0 covergence though nothing to keep generating convection. micro-wave imagery reveals this is still poorly organized were it counts.

what ya think?

[HurricaneDREW92]

Think we'll see 50/80 at 8pm but that may be a bit liberal.

[jinftl]

97L will be entering the E. Caribbean sea - an area know as the graveyard of systems due to strong trade winds - once we get this system south of Hispanola, then chances of development could go up quite a bit - according to Dr. Jeff Masters, we still may be 72-96 hours away from this having the best shot of developing.

"The main factor keeping the disturbance from developing over the next two days would appear to be the fact that 97L is quite large, and is stretched out from east to west over a wide expanse. Large, elongated systems like 97L usually take several days to consolidate and spin up.

Another factor that will likely retard development is the presence of strong surface trade winds over the Eastern Caribbean ahead of 97L, south of the Dominican Republic. These strong trade winds are a common feature of the Eastern Caribbean, and make the region something of a hurricane graveyard. As the surface wind flow to the west of 97L accelerates into this wind max, air will be sucked from aloft downward towards the surface, creating sinking air, interfering with the formation of thunderstorm updrafts.

The best chance for development of 97L would appear to be on Wednesday or Thursday, when the disturbance reaches the Central Caribbean."

[TropicalAnalystwx13]

I doubt anything comes of this before it reaches Hispaniola's longitude and beyond. The eastern Caribbean is famous for holding systems down because stable air is advected off South America and the trade wind flow is accelerated, lowering convergence (the John Hope law states that if a system isn't already developed before entering the Caribbean, it is UNLIKELY (not impossible) to become a tropical cyclone until 75W). However, being on the southeast side of an upper-level low during this journey should keep it active convectively. This should be near Jamaica's longitude in 3 days, where we might see real development. Let's hope we don't get a developed system by that time because the upper-air pattern is forecast to be phenomenal and the Ocean Heat Content should allow for rapid intensification. Just something to watch for now.

['CaneFreak]

Not a chance. 40/50 is even generous at this point. The dying convection now speaks VOLUMES about the organization of this disturbance. Will be at least a couple days before this does anything.

Think we'll see 50/80 at 8pm but that may be a bit liberal.

[HurricaneDREW92]

Not a chance. 40/50 is even generous at this point. The dying convection now speaks VOLUMES about the organization of this disturbance. Will be at least a couple days before this does anything.

Think we'll see 50/80 at 8pm but that may be a bit liberal.

Its DMIN. If they are conservative they might go 40/60. But the actual chances are like 30/90

[stormlover2013]

Lol that guy has made like 10 predictions in 24 hours lol

[jinftl]

30/50 or 30/60 seems reasonable at 8pm

Not a chance. 40/50 is even generous at this point. The dying convection now speaks VOLUMES about the organization of this disturbance. Will be at least a couple days before this does anything.

Think we'll see 50/80 at 8pm but that may be a bit liberal.

[lester]

Think we'll see 50/80 at 8pm but that may be a bit liberal.

It's very liberal, especially the fact that it's entering a bad spot to be in historically for a developing tropical cyclone. Cyclones don't form quickly all the time, sometimes it takes days for systems to develop. Patience, young grasshopper, patience.

[HurricaneDREW92]

Think we'll see 50/80 at 8pm but that may be a bit liberal.

It's very liberal, especially the fact that it's entering a bad spot to be in historically for a developing tropical cyclone. Cyclones don't form quickly all the time, sometimes it takes days for systems to develop. Patience, young grasshopper, patience.

Well probably has a 90% at 5 days, 30 in the next 48hrs but still sticking with 50/60-80 in the next TWO.

[stormlover2013]

Keeps changing his mind lol