ATL: INVEST 92L - Discussion

[SunnyThoughts]

looks like its broken in half...top half heading north, and southern half heading towards Yucatan. http://weather.msfc.nasa.gov/GOES/goeseastconus.html

[ROCK]

more down by Belize and above as you can see a MLC taking shape...the stuff at top is what the models are shearing off and sending to MS/AL....even the NAM develops a little bitty low in this mess....

[cycloneye]

2 PM.

A BROAD AREA OF LOW PRESSURE...ACCOMPANIED BY A LARGE BUT
DISORGANIZED AREA OF CLOUDINESS AND SHOWERS...HAS MOVED OVER THE
YUCATAN PENINSULA THIS MORNING. DEVELOPMENT OF THIS SYSTEM IS NOT
ANTICIPATED WHILE IT MOVES OVER LAND...BUT THERE IS STILL POTENTIAL
FOR DEVELOPMENT ONCE THE DISTURBANCE MOVES OVER THE GULF OF MEXICO
ON FRIDAY. AFTER THAT TIME...THE LOW IS FORECAST TO MOVE TOWARD THE
CENTRAL GULF OF MEXICO WHERE THE UPPER-LEVEL WINDS WOULD ONLY FAVOR
SLOW DEVELOPMENT...IF ANY. THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS...AND A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 5 DAYS.

[BigA]

Based on the limited data at our disposal (mainly visible imagery and the 850 mb vorticity plots), I would say that the center of the action (or whatever action there is at this point) is near the northern tip of Belize. That is where there is low-level convergence, and about where 850 mb vorticity is strongest. To the extent that there is near-surface convergence, the strongest convergence looks to be over that area. It is also closest to an area of upper-level high pressure centered over southeast Mexico

To me this would indicate that the system is going to head toward the BOC, as most of the models are now indicating. From there, it is still possible (even likely that it will get pulled northward by the trough.


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

[ROCK]

2 PM.

A BROAD AREA OF LOW PRESSURE...ACCOMPANIED BY A LARGE BUT
DISORGANIZED AREA OF CLOUDINESS AND SHOWERS...HAS MOVED OVER THE
YUCATAN PENINSULA THIS MORNING. DEVELOPMENT OF THIS SYSTEM IS NOT
ANTICIPATED WHILE IT MOVES OVER LAND...BUT THERE IS STILL POTENTIAL
FOR DEVELOPMENT ONCE THE DISTURBANCE MOVES OVER THE GULF OF MEXICO
ON FRIDAY. AFTER THAT TIME...THE LOW IS FORECAST TO MOVE TOWARD THE
CENTRAL GULF OF MEXICO WHERE THE UPPER-LEVEL WINDS WOULD ONLY FAVOR
SLOW DEVELOPMENT...IF ANY. THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS...AND A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 5 DAYS.

doesnt make any sense...5 days? really....this will be over in 3 days. How can they say 5 days when this will be long gone in 5 days UNLESS they think its going to hang out awhile...hmmmmm

[ROCK]

Based on the limited data at our disposal (mainly visible imagery and the 850 mb vorticity plots), I would say that the center of the action (or whatever action there is at this point) is near the northern tip of Belize. That is where there is low-level convergence, and about where 850 mb vorticity is strongest. To the extent that there is near-surface convergence, the strongest convergence looks to be over that area. It is also closest to an area of upper-level high pressure centered over southeast Mexico

To me this would indicate that the system is going to head toward the BOC, as most of the models are now indicating. From there, it is still possible (even likely that it will get pulled northward by the trough.


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

agree

[USTropics]

To me, there appears to still be a cut off low spinning near the tip of the Yucatan, and this may be what spins down to the surface and heads towards the NGOM states. You can see it in the loop below.

http://mkwc.ifa.hawaii.edu/satellite/sa ... type=flash

If you're looking at the vorticity at 850mb, it's really down by Belize, and I think this may be what eventually makes it towards the BOC.

[Dean4Storms]

Tip of Yucatan continues to look interesting. IMO

http://www.ssd.noaa.gov/PS/TROP/floater ... -long.html

Sure does, bigger rotation there for sure.

[BigA]

2 PM.

A BROAD AREA OF LOW PRESSURE...ACCOMPANIED BY A LARGE BUT
DISORGANIZED AREA OF CLOUDINESS AND SHOWERS...HAS MOVED OVER THE
YUCATAN PENINSULA THIS MORNING. DEVELOPMENT OF THIS SYSTEM IS NOT
ANTICIPATED WHILE IT MOVES OVER LAND...BUT THERE IS STILL POTENTIAL
FOR DEVELOPMENT ONCE THE DISTURBANCE MOVES OVER THE GULF OF MEXICO
ON FRIDAY. AFTER THAT TIME...THE LOW IS FORECAST TO MOVE TOWARD THE
CENTRAL GULF OF MEXICO WHERE THE UPPER-LEVEL WINDS WOULD ONLY FAVOR
SLOW DEVELOPMENT...IF ANY. THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS...AND A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 5 DAYS.

doesnt make any sense...5 days? really....this will be over in 3 days. How can they say 5 days when this will be long gone in 5 days UNLESS they think its going to hang out awhile...hmmmmm

I think the 5 days is just the NHC's standard way of saying between 2 and 5 days.

[ROCK]

2 PM.

A BROAD AREA OF LOW PRESSURE...ACCOMPANIED BY A LARGE BUT
DISORGANIZED AREA OF CLOUDINESS AND SHOWERS...HAS MOVED OVER THE
YUCATAN PENINSULA THIS MORNING. DEVELOPMENT OF THIS SYSTEM IS NOT
ANTICIPATED WHILE IT MOVES OVER LAND...BUT THERE IS STILL POTENTIAL
FOR DEVELOPMENT ONCE THE DISTURBANCE MOVES OVER THE GULF OF MEXICO
ON FRIDAY. AFTER THAT TIME...THE LOW IS FORECAST TO MOVE TOWARD THE
CENTRAL GULF OF MEXICO WHERE THE UPPER-LEVEL WINDS WOULD ONLY FAVOR
SLOW DEVELOPMENT...IF ANY. THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS...AND A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 5 DAYS.

doesnt make any sense...5 days? really....this will be over in 3 days. How can they say 5 days when this will be long gone in 5 days UNLESS they think its going to hang out awhile...hmmmmm

I think the 5 days is just the NHC's standard way of saying between 2 and 5 days.

I still question the logic...and I even made a "D" in college logic and even I know this doesnt sound right....

[Kalrany]

2 PM.

A BROAD AREA OF LOW PRESSURE...ACCOMPANIED BY A LARGE BUT
DISORGANIZED AREA OF CLOUDINESS AND SHOWERS...HAS MOVED OVER THE
YUCATAN PENINSULA THIS MORNING. DEVELOPMENT OF THIS SYSTEM IS NOT
ANTICIPATED WHILE IT MOVES OVER LAND...BUT THERE IS STILL POTENTIAL
FOR DEVELOPMENT ONCE THE DISTURBANCE MOVES OVER THE GULF OF MEXICO
ON FRIDAY. AFTER THAT TIME...THE LOW IS FORECAST TO MOVE TOWARD THE
CENTRAL GULF OF MEXICO WHERE THE UPPER-LEVEL WINDS WOULD ONLY FAVOR
SLOW DEVELOPMENT...IF ANY. THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS...AND A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 5 DAYS.

doesnt make any sense...5 days? really....this will be over in 3 days. How can they say 5 days when this will be long gone in 5 days UNLESS they think its going to hang out awhile...hmmmmm

I think the 5 days is just the NHC's standard way of saying between 2 and 5 days.

Kind of… I recall (I think in one of the Pacific threads) that the 5 day encompasses the time frame of the full five days from issuance. So, the 2 days meaning anytime in the 0-48 hour range, while the 5 days any time in the 0-120hr range. This was questioned as the 5 day was never less than the 2 day, but was explained as if there was only a chance of development in the first 2 days, then that chance was also the 5 day as well. So, while there may be an increased chance in the 5 day range, it is possible to have the peak formation time prior to the fifth day. So even if it is to be onshore/dissipated at day 5, that does not mean that the peak of day 3 is not what they are looking at for chances. That’s all.

[wxman57]

Don't try to read something into the NHC's wording that isn't there. They issue an outlook for the next 48 hours and through the next 5 days (between 48 hours and 120 hours). Just because they don't specifically say that the disturbance probably won't be around by that 5th day doesn't mean the statement of development potential through 5 days is invalid.

[cycloneye]

18z Best Track.

AL, 92, 2013081518, , BEST, 0, 193N, 883W, 25, 1010, DB

[Blinhart]

Looking at a lot of the models they think there is a good chance that this system could be around for up to a week (if I am reading them right) http://derecho.math.uwm.edu/models/al922013.png or at least 5 days so there is a possibility that the energy will not all be picked up by the trough.

[BigA]

Looking at a lot of the models they think there is a good chance that this system could be around for up to a week (if I am reading them right) http://derecho.math.uwm.edu/models/al922013.png or at least 5 days so there is a possibility that the energy will not all be picked up by the trough.

Not a full week, but yes, some of the models do have 92L or what it ends up becoming staying over the Gulf for up to 5 days or a bit longer. It is conceivable that it misses the trough if it takes a more southerly track. What I don't fully understand (but that doesn't make it impossible) is how the models have it moving slowly northward. It seems if it moves northward that would be the result of a trough, and it would be a more rapid motion.

[Rgv20]

Afternoon Discussion from the NWS San Antonio

.LONG TERM (SATURDAY THROUGH THURSDAY)...
THE UPPER LEVEL HIGH WILL REMAIN CENTERED OVER THE 4 CORNERS REGION
OVER THE WEEKEND INTO EARLY NEXT WEEK. THIS WILL ALLOW AFTERNOON
TEMPERATURES TO EASE DOWNWARD TO AROUND NORMAL. A WEAK SW TO NE
ORIENTATED MID LEVEL TROF EVOLVES OVER THE TEXAS COAST BY THE
MIDDLE OF NEXT WEEK. THIS WILL ALLOW FOR AN ACTIVE SEA-BREEZE
BOUNDARY TUESDAY THROUGH THURSDAY WITH THE BEST INLAND SPREAD OF
CONVECTION OCCURRING ON WEDNESDAY AND THURSDAY. THE PCPN FORECAST
EARLY NEXT WEEK WILL BE DEPENDENT ON WHAT OCCURS OVER THE GULF
THIS WEEKEND. A TROPICAL WAVE IS MOVING ACROSS THE YUCATAN THIS
AFTERNOON AND WILL ENTER THE BAY OF CAMPECHE ON FRIDAY. THIS WAVE
HAS THE POTENTIAL TO BECOME A TROPICAL STORM. THE LATEST SPAGHETTI
PLOTS HAVE THIS SYSTEM MOVING ONSHORE ANYWHERE FROM VERACRUZ TO
BROWNSVILLE TO HOUMA. BEARS WATCHING.

[nautical wheeler]

That ULL is just grinding away at it. Is it supposed to relax anytime soon?

[tropicwatch]

The wind shear has come down quite a bit. If the system can get away for Yucatan we might actually seem some organization.

[ozonepete]

That ULL is just grinding away at it. Is it supposed to relax anytime soon?

You are making an excellent observation. That ULL has indeed been grinding away at the western side of 92L. But it's expected to weaken considerably and move northward away from this very quickly this evening and tonight. That is why shear is forecast to drop significantly over the whole general area near the Yucatan. Looking at the satellite loops it's clearly dropping a lot already.

In addition, Ivanhater made a really good point last night: these messy disturbances that move over the Yucatan and have stretched out vorticity over that peninsula tend to reorganize and put down an LLC just north of the Yucatan if there's a decent MLC anywhere near the northern Yucatan (which there is). The reason is because the vorticity over the water allows building thunderstorms more easily than over the land portion (more theta-e fuel). This in turn allows the thunderstorms to cluster over the water as they fizzle over the land. Disturbances like this that have somewhat of an MLC always have multiple LLCs that form and die out and rotate around each other until one gets under the MLC and stacks with it, and that usually happens where the most convection is. Given that scenario, it would seem that this will organize tonight and start getting an LLC just north of the Yucatan, not down over land in the southern Yucatan.

['CaneFreak]

Agreed. An upper level ANTI-cyclone is forming over the western GOM now and I would think that if this ends up missing the trough and heads west, it will have a whole lot better environment to work with and we could get a decent system out of this current mess. Do you think this misses the trough?

Edit: Layer mean wind analysis says that unless this intensifies rapidly, the steering currents will be relatively weak and with a ridge developing over N TX, this would have to head towards the TX/MX coast I would think.

http://tropic.ssec.wisc.edu/real-time/dlmmain.php?&basin=atlantic&sat=wg8&prod=dlm1&zoom=&time=

You are making an excellent observation. That ULL has indeed been grinding away at the western side of 92L. But it's expected to weaken considerably and move northward away from this very quickly this evening and tonight. That is why shear is forecast to drop significantly over the whole general area near the Yucatan. Looking at the satellite loops it's clearly dropping a lot already.

In addition, Ivanhater made a really good point last night: these messy disturbances that move over the Yucatan and have stretched out vorticity over that peninsula tend to reorganize and put down an LLC just north of the Yucatan if there's a decent MLC anywhere near the northern Yucatan (which there is). The reason is because the vorticity over the water allows building thunderstorms more easily than over the land portion (more theta-e fuel). This in turn allows the thunderstorms to cluster over the water as they fizzle over the land. Disturbances like this that have somewhat of an MLC always have multiple LLCs that form and die out and rotate around each other until one gets under the MLC and stacks with it, and that usually happens where the most convection is. Given that scenario, it would seem that this will organize tonight and start getting an LLC just north of the Yucatan, not down over land in the southern Yucatan.