ATL : HARVEY - Tropical Depression - Discussion

[GCANE]

West Cuba fired off some very heavy afternoon thunderstorms and the debris looks to be rotating into the ML dry air to 93L's east.

http://www.ssd.noaa.gov/goes/east/watl/flash-wv.html

This could be the shot 93L needed.

Might have a nicely ramping up TC by sunrise.

[ozonepete]

Nice observation. You're becoming the maven here on mid-level moisture. It's amazing how many times people miss that key element for formation and survival of a TC. (Including myself too often.)

[ozonepete]

BTW, it was that (what appears to be) developing TUTT to the north and northeast of 93L that pushed the moisture southward towards its northern and eastern sides. And a TUTT to the northeast of a developing cyclone is advantageous for development because it helps vent the system at upper levels on the northeast side and thus helps an upper level anti-cyclone to develop.

[GCANE]

:uarrow: Nice observation. You're becoming the maven here on mid-level moisture. It's amazing how many times people miss that key element for formation and survival of a TC. (Including myself too often.)

Thanks Phil

[BigA]

Looks to me like it has gained enough latitude so that it will get over the "knee" of Honduras and Nicaragua, though if it is only 20-50 miles north it won't strengthen much. Still expect a TC out of this.

[GCANE]

BTW, it was that (what appears to be) developing TUTT to the north and northeast of 93L that pushed the moisture southward towards its northern and eastern sides. And a TUTT to the northeast of a developing cyclone is advantageous for development because it helps vent the system at upper levels on the northeast side and thus helps an upper level anti-cyclone to develop.

Agreed.

Also when a TC tracks into an anti-cyclone it allows the vorticity column to expand vertically since an anti-cyclone is a localized rise in the tropopause.

That in turn pulls the vorticity (PV anomaly) in radially causing the angular rotation to increase due to conservation of angular momentum.

The old spinning skater pulling his arms in analogy.

Anyway, that is in fact what appears to be happening with 93L at this time.

[Brent]

BEST TRACK: AL08, 154N 815W, 30kts, 1006mb, TD EIGHT
RENUMBER al93 al08

[GCANE]

Finally!

Getting a hot-tower firing. Its small and only lasted about 1/2 hr.; but, a solid sign 93L is ramping up.

[ozonepete]

Yeah, finally. It has to be at least a TD. And Hondurans need to know about this.

Although it looks weak enough on the left semi-circle, which is climatologically what you expect, it still has the capability of causing dangerous rainfall and mudslides there.

[ozonepete]

Nice feeder band has developed, feeding moisture into the southeast quadrant.

[HurrMark]

Now the question is whether it will get strong enough to get to Harvey or will remain an unnamed depression. Given the current latitude (15.4), the poor organization convectively speaking, and the fact that it isn't going to traverse much to the north, I will say that the chances are probably more likely than not that it will just stay TD Eight...just my opinion...not official. My guess is landfall by noon tomorrow.

[ozonepete]

With no shear to speak of, no mid-level dry air at all, the center staying north of Honduras, and it slowing down a lot over the next 24 hours, I would say a strong tropical storm close to a hurricane by the time it landfalls in Belize. The only negative is the proximity to land in Honduras, but the northwesterly winds pushing up against the mountains could actually enhance the circulation strength.

[ozonepete]

the big question is will it curve left into Honduras. That's why I'm dying to see the NHC track forecast.

[HurrMark]

TROPICAL DEPRESSION EIGHT ADVISORY NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082011
1100 PM EDT THU AUG 18 2011

...TROPICAL DEPRESSION FORMS IN THE WESTERN CARIBBEAN SEA...


SUMMARY OF 1100 PM EDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...15.4N 82.1W
ABOUT 80 MI...125 KM ENE OF CABO GRACIAS A DIOS ON NIC/HON BORDER
ABOUT 430 MI...690 KM ESE OF BELIZE CITY
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES

[wxman57]

It may be inland over Honduras by sunrise. NHC track has the center very near the coast of Honduras at 12Z. Could become a weak TS as it skirts along the coast of Honduras but that's about it.

[Tampa_God]

Min. Tropical Storm before slamming into Honduras/ South America? It's close, but it needs to get it's act together.

[cycloneye]

the big question is will it curve left into Honduras. That's why I'm dying to see the NHC track forecast.

[HurrMark]

Track takes it inland tomorrow morning...then slightly reemerges off that coastal area angles in a more southerly direction...may have a little time to become Harvey, but I think it's 50-50 at best...probably more 70-30 remains TD Eight in my opinion.

[ozonepete]

Interesting. It makes TS after landfall. LOL.

[HurrMark]

A recentering of the storm by even a few ticks of latitude northward could mean a world of difference...