Invest 93L: do we have a problem?

2010 June 25

Invest 93L has had a pretty nice low-level circulation (LLC) going for a day or so now– the problem is everyone’s been worried about the convection south of Jamaica trying to develop a mid-level swirl when our LLC had been a couple hundred miles to the SW.

93L #1

93L #2

This afternoon it looks like our convection is propagating towards our LLC and our LLC is even retrograding back towards the height falls caused by the convection. A symbiotic relationship that can only happen in a wonderfully low shear environment!

93L #3

Speaking of shear, we can see the storm’s in a bulls-eye for low 850-200 mb shear (yellow contours, low numbers means less shear = good for tropical cyclone development since the warm core can become vertically stacked). Broad (albeit weak) area of satellite derived cyclonic vorticity in the area (orange contour) which is a good sign as well. However, strong sheer exists across the Yucatan channel (20, 30, 40 m/s yellow contours at the top of the images). Unfortunately for potential Alex or fortunately for Gulf residents, this is really the only conceivable path a landfalling system could follow if it were to develop and make it into the Gulf as anything of any substance. Two models (GFS and CEM) I quickly looked at don’t lift this shear out of the area anytime soon (see below, the pink colors across southern Gulf and Cuba — the two images are for Friday night, but there’s not a whole lot of movement through day 3). Although a few models really blow this system up and show a landfalling cyclone in LA/MS, I just can’t see that unless the models are doing a bad job of the synoptic environment (and they theoretically should have a much better handle on that than the actual cyclogenesis). Should the storm follow the dynamical models that move it NW, any deep convection will be quickly sheared away and the central dense overcast (CDO) will separate from the LLC.

It’s only bet for survival (if the models verify) would be to trek southward (weaker storms are more easily steered by low-level flow anyways) across the Yucatan and into the Bay of Campeche. With this track, it’s unlikely a cyclone could spend enough time over open water to really maintain any symmetric core.

93L #4

93L #5

So we might have TD1 or even Alex in the next 24-48 hours. However, unless I see otherwise, I’m highly skeptical of the “doom and gloom” potential SOME people are already trying hard to pick up on. Whatever is forming, it looks highly probably we’ll see it cross the Yucatan, emerge in the Bay of Campeche, and then likely move inland over central Mexico a few days later.

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