Model Runs & Discussions of GOM-Bahamas

[Stratosphere747]

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_006m.gif

[cycloneye]

00z GFS 200mb at 24 hours

Strong upper winds in gulf.

[MiamiensisWx]

If you look at this loop, you can see conditions are quite hostile in the W Bahamas. Note the outflow boundaries: this is an indication of upper-level shear. The shear actually appears to be a partial contributor to the low-level convergence in the area. The divergence is too strong for consolidation, so any potential LLC would lose its associated convection and/or remain broad and weak. Personally, I don't see a developing sfc low near Andros Island, Bahamas. I do see a possible broad rotation over the islands, but it's the league of shear. Finally, the convection near the Turks and Caicos (E of the Bahamas) isn't situated an an ideal environment: it is over an area of weaker low-level convergence and 850 mbar vorticity. Additionally, it is susceptible to competition from adjacent thunderstorms. I don't see any low-level circulation there. I will need to see further persistence before I think it has a shot, in spite of the fact that it's situated in an environment of lower shear. The possible larger circulation is situated over the W Bahamas beneath strong shear.

http://www.ssd.noaa.gov/goes/east/gmex/loop-vis.html

http://www.ssd.noaa.gov/goes/east/tatl/loop-ir2.html

Can a professional meteorologist chime in here on my thoughts?

[cycloneye]

00z GFS 200mb at 42 hours

Upper Winds still screaming.

[cycloneye]

00z GFS 200mb at 54 hours

50 kt upper winds.

[Extremeweatherguy]

low forms in eastern GOM (54 hrs) = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_054s.gif

[ROCK]

low forms in eastern GOM (54 hrs) = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_054s.gif

but how can it? is it seeing the ULL as the low itself?

[Steve]

>>I buy the first part but not the last. I don't see the upper low backing away. I think it will be the kicker to get the sfc low started, but I think the sfc low will have to contend with it...and may have to work thru it. I don't see the upper low backing away anytime soon. If it can sink south and whatever develops can work west of the low...then the upper environment will be really good...but that won't happen till later...like the weekend...and once it is in the central GOM...

At least since August, there have been no static upper troughs across the Gulf whenever there were surges or tropical waves coming in from the east. I'm going to have to disagree with you and AFM about the early game, though I think we get on the same page toward the weekend. We also disagree on potential intensity. You guys are WAY underplaying the threat (should a system materialize). I need to go to bed, and I'm only on Page 41 of 48. Ugh.

Steve

[cycloneye]

00z GFS 200mb at 66 hours

Still fierce upper winds in parts of GOM.

[Ptarmigan]

Interesting discussions, AFM/Derek. I agree, AFM, that the upper low could be the spark that gets some kind of low going, possibly near Florida on one side or the other. But the question I have is how the global models would handle the upper-level features (i.e., the low) given that they don't really forecast tropical systems well. 5-day forecasts are often pretty bad as far as upper wind predictions, particularly if the model "thinks" the low its developing isn't tropical in nature. So maybe the shear you're seeing isn't really going to be there by Friday?

This system really does have me concerned. With a ridge building to the north and a slow west movement beneath it, it would seem like quite a favorable environment for TC development/intensification. The "fly in the ointment" is that upper low. What if the models are wrong with its strength and/or location (or even its existence) by Friday? My gut is telling me that this system could be a real problem. Or maybe it's all the Corn Chex I just ate.

I am just an amateur and I too have this gut feeling that the tropics is up to no good. Even all the local mets on the news say something could brew in the tropics. At best, it will just mean more rain. Hopefully, this is wrong. I do like Corn Chex, preferable the Chex Mix with the worchester sauce.

[jhamps10]

and GFS does not move the surface low at all between 54 and 66, but it DOES intensify it. different than 18z, where it stalls it and kills it.

[Extremeweatherguy]

78 hrs..

low in central GOM = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_078s.gif

upper level winds lightening considerably = http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_078s.gif

[Stormcenter]

00z GFS 200mb at 66 hours

Still fierce upper winds in parts of GOM.

If these upper winds pan out this possible develop has zero chance
of becoming anything significant at the surface in the GOM. IMO

[cycloneye]

00z GFS 200mb at 78 hours

Less shear in general,but still some South upper winds a little strong.

[ROCK]

Am I wrong in saying how does this low EVEN form in such hostile conditions?

[Extremeweatherguy]

By 78 hours the upper level winds are lightening up a lot.

Compare:

48 hrs - http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_048s.gif

78 hrs - http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_078s.gif

As the mets have said, the best chance for significant development will be in the central GOM as these upper level winds die down.

[Extremeweatherguy]

90 hrs..

low heading west in the GOM = http://www.nco.ncep.noaa.gov/pmb/nwprod ... n_090s.gif

Light upper level winds over the low = http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_090s.gif

[wxmann_91]

Am I wrong in saying how does this low EVEN form in such hostile conditions?

The low is progged to work from the upper levels down to the SFC.

The Euro actually backs off the upper low to the SE while an upper anticyclone develops over the future system... as does the GFS in later periods. That is an extremely favorable upper air pattern, as we've seen with STY Wipha.

[cycloneye]

00z GFS 200mb at 90 hours

Less shear in West GOM than in EGOM.

[ROCK]

Am I wrong in saying how does this low EVEN form in such hostile conditions?

The low is progged to work from the upper levels down to the SFC.

The Euro actually backs off the upper low to the SE while an upper anticyclone develops over the future system... as does the GFS in later periods. That is an extremely favorable upper air pattern, as we've seen with STY Wipha.

Ahhhh......now I see the light.....