Invest 99L E of Lesser Antilles,Comments,Sat Pics,Etc #3

[WindRunner]

LLC is evident this morning, and the convection is still being blown a little bit off of the center, but it is persistent. I still don't think this deserves recon at this point, but I guess we'll see in the next couple of hours if that will happen or not.

There is no LLC. If you follow the individual cloud elements...you will see that it has a storm-relative circulation...but not ground relative. The around south of the vorticity center is at best an area of light and variable winds. There are no eastward moving clouds.

Ok, yeah, I see that now. That was just my quick glance at the system, and I see it's actually pretty obvious that there's a lull on the southern edge of the system. It appears that there may have been a little eastward movement earlier, but only marginally so, and whatever that consisted of is gone now.

[curtadams]

Looking at the RGB loop, it's clearly a cyclone in the casual sense. Virtually all the remaining convection is being generated from the sheared updraft from the LLC, and it's an ongoing process. It may not be a cyclone formally because the circulation isn't closed earth-relative but it's functionally a cyclone and not just a wave or even thunderstorms associated with a low. The quickscat from 9Z shows some barbless winds - does that mean it can't determine direction?

[Air Force Met]

I think the reason it's not a TD yet may be because they can't send the plane out till it gets close enough

The reason it's not a TD yet is because there is no LLC.

I am going to have to disagree with you there Air Force Met...every 925 mb vorticity map I have looked at shows a well defined LLC, it may not be quite at the surface, but there is a circulation in the lower levels of the atmosphere...if I am correct? 925mb = 2500ft ....which is pretty darn close to the surface....

Lower levels are anything below 6500 feet. However, in the tropics, when the talk about an LLC, we are talking about a sfc circulation...pure and simple...not about something above the sfc...but a circulation at the sfc and with that you must have a west wind of some kind.

Vorticity does not a LLC make. Vorticity is just that...vorticity. Vorticity is measuring the amount of spin an air particle has...NOT the entire area itself. If you have an east wind at 925mb blowing at 15 knots...and another east wind at 925mb blowing at 45 knots located 50 nm north of it...you will see TREMENDOUS vorticity on a chart...

But you will not have a LLC. You still have east winds.

I can show you a hundred areas of lower level vorticity at any given time that do not have a closed circulation. Just because you see vorticity does not mean you have west winds at the sfc or at the area where the vorticity is located.

This is true at ANY level. Take a look at a 500mb/vort chart.

http://weather.unisys.com/gfs/12h/gfs_500_12h.html

You have vort centers everywhere...but only a few of those actually have closed circulations.

[Air Force Met]

What is the technical definition of an LLC? I have seen winds blow from SE to NE to NW to W to SW....? I am very interested...

A LLC is a closed circulation. You really need to see the whole picture...beause with a NW wind...your wave might be tilted a certain way that you might have a cusp instead of a closed LLC. Same with SW winds. IF the wave is tilted NE-SW...those SW winds might be part of a cusp...and may not actually represent a closed LLC.

The best way is to see the winds from WNW-WSW. It's hard to streamline an open wave with those directions...but it can be done with NW winds or SW winds.

[senorpepr]

The quickscat from 9Z shows some barbless winds - does that mean it can't determine direction?

Wind barbs without a "thumb" (or wind barbs that look like a line without anything sticking off of it) indicates wind speeds of 2 knots or less.

If a direction cannot be determine (i.e. variable winds), a circle is used.

[wxman57]

Here's a recent McIDAS image. I see two small eddies rotating cyclonically. Many outflow boundaries moving away to the northwest and north. One squall area on the east side. Shear remains strong. No significant low-level convergence means it'll have a hard time organizing.

http://myweb.cableone.net/nolasue/99Lf.gif

[Thunder44]

Tropical Weather Outlook

Statement as of 11:30 am EDT on July 31, 2006


For the North Atlantic...Caribbean Sea and the Gulf of Mexico...
The tropical wave located about 250 miles east of the Leeward
Islands is moving west-northwestward at 15-20 mph. This system
remains well-organized but the associated shower activity remains
limited. Environmental conditions are only marginally conducive
for tropical cyclone development. Locally heavy showers and strong
gusty winds in squalls are likely over portions of the Lesser
Antilles during the next day or two.
Cloudiness and disorganized showers extend northeastward from the
vicinity of the Windward Passage into the Atlantic for a few
hundred miles. Upper-level winds are forecast to remain
unfavorable for development of this system. However...locally
heavy rains can be expected over portions of eastern Cuba and
Hispaniola during the next day or so.
An area of low pressure located about 150 miles east-southeast of
Cape Hatteras North Carolina is moving slowly east-southeastward.
Although the associated shower activity is not well-organized at
this time...this system has some potential for development over the
next day or so.
Elsewhere...tropical storm formation is not expected through
Tuesday
$$
forecaster Pasch/Roberts

[Thunder44]

Code: Select all

854
NOUS42 KNHC 311500
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, TPC/NATIONAL HURRICANE CENTER, MIAMI, FL.
1100 AM EDT MON 31 JUL 2006
SUBJECT: TROPICAL STORM PLAN OF THE DAY (TSPOD)
         VALID 01/1100Z TO 02/1100Z AUG 2006
         TSPOD NUMBER.....06-062

I.  ATLANTIC REQUIREMENTS
    1. SUSPECT AREA (LESSER ANTILLES)
       FLIGHT ONE                     FLIGHT TWO
       A. 01/1800Z                    A. 02/0000Z
       B. AFXXX 01DDA INVEST          B. NOAA9 02DDA SURV
       C. 01/1700Z                    C. 01/1730Z
       D. 18.0N 62.5W                 D. NA
       E. 01/1730Z TO 01/2330Z        E. NA
       F. SFC TO 10,000 FT            F. 41,000 TO 45,000 FT

       FLIGHT THREE
       A.  02/0600,1200Z
       B.  AFXXX 0303A CYCLONE
       C.  02/0500Z
       D.  19.0N 64.5W
       E.  02/0530Z TO 02/1200Z
       F.  SFC TO 10,000 FT

    2. OUTLOOK FOR SUCCEEDING DAY.....CONTINUE 6-HRLYS IF SYSTEM
       DEVELOPS AND REMAINS A THREAT.

    3. REMARKS:  MISSIONS PREVIOUSLY SCHEDULED FOR THIS SYSTEM WERE
         CANCELED BY NHC AT 31/1200Z.


    4. SUSPECT AREA (OFF CAROLINA COAST)
       FLIGHT ONE                    FLIGHT TWO
       A.  01/2100Z                  A.  02/1200Z
       B.  AFXXX 01EEA INVEST        B.  AFXXX 0204A CYCLONE
       C.  02/1715Z                  C.  02/0800Z
       D.  33.0N 70.0W               D.  32.0N 69.0W
       E.  01/2030Z TO 02/0000Z      E.  02/1130Z TO 1500Z
       F.  SFC TO 10,000 FT          F.  SFC TO 10,000 FT

     5.  SUCCEEDING DAY OUTLOOK CONTINUE 12 HRLY FIXES IF SYSTEM
           DEVELOPES AND IS A THREAT

The flight has been cancelled for today for 99L, but scheduled again for tomorrow afternoon. More flights are scheduled for 90L tomorrow.


EDIT: (by senorpepr) to put data in code format for better alignment.

[Derek Ortt]

http://www.nhc.noaa.gov/text/MIAREPRPD.shtml?

recon cancelled for today, as I expected it would be

[Air Force Met]

http://www.nhc.noaa.gov/text/MIAREPRPD.shtml?

recon cancelled for today, as I expected it would be

Yep...no doubts here they wouldn't fly...unless they wanted the practice.

[Thunder44]

http://www.nhc.noaa.gov/text/MIAREPRPD.shtml?

recon cancelled for today, as I expected it would be

Yep...no doubts here they wouldn't fly...unless they wanted the practice.

Do you or any of the mets believe that system is "well-organized"?

[Air Force Met]

http://www.nhc.noaa.gov/text/MIAREPRPD.shtml?

recon cancelled for today, as I expected it would be

Yep...no doubts here they wouldn't fly...unless they wanted the practice.

Do you or any of the mets believe that system is "well-organized"?

It's well organized at the sfc as far as the sfc structure goes. The thing that is working against it is the lack of convection (dry air) and shear. If it was in a moist environment and in a low shear environment...the game would be on.

[Derek Ortt]

its better than yesterday, but thats as far as I would go

[curtadams]

Shear is relaxing - both visibly and by forecast. Convection is moving closer to the center. Wind shear map shows it's about to pass from the current fairly high shear to pretty low shear today. Predictably, convection continues to improve. Should be TD easily by tonight, and could become one any minute (remember quickscat showed it was only 2 mph short of a west wind.)

[Scorpion]

Shear is relaxing - both visibly and by forecast. Convection is moving closer to the center. Wind shear map shows it's about to pass from the current fairly high shear to pretty low shear today. Predictably, convection continues to improve. Should be TD easily by tonight, and could become one any minute (remember quickscat showed it was only 2 mph short of a west wind.)

Wow, you're usually pretty bearish. I'm definitely watching this closer now.

[skysummit]

Curta...IMO, it still has a good ways to go before getting to TD status. Remember, we don't even have recon going anylonger to confirm anything. I wouldn't say TD easily by tonight.......that's if the NHC doesn't jump on the trigger pulling.

[NONAME]

For the First time in days 99L Has some good convection over the center now there is red in the IR,

[Air Force Met]

For the First time in days 99L Has some good convection over the center now there is red in the IR,

Let's keep it real...the convection is still east of the area of vorticity... and it doesn't have a center yet...just a center of vorticity. If the convection was over the center...you wouldn't be able to see it....and we wouldb't be able to discuss whether or not it was closed...because it would be covered in clouds.

But convection is on the increase...but the dry air is still everywhere....so don't be surprised if the tops warm in a few hours.

[curtadams]

Wow, you're usually pretty bearish. I'm definitely watching this closer now.

*Me* bearish? That says something about this site. I can tell you that on average things end up less developed than I honestly expect - but not outrageously so.

[curtadams]

Curta...IMO, it still has a good ways to go before getting to TD status. Remember, we don't even have recon going anylonger to confirm anything. I wouldn't say TD easily by tonight.......that's if the NHC doesn't jump on the trigger pulling.

NHC always drags its feet on TD upgrades, and they will wait until something really conclusive comes through, like a 2.5 Dvorak or an unambiguous quickscat. And that's fine, because a 25 kt TD isn't a crisis. But I do think it's very close to a real closed circulation, which would make it a TD even if the NHC hasn't yet issued an upgrade, and it's strengthening.