Tuesday, July 29, 2014

Enjoy the Dry Air While You Can!

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:

- welcomed break in the humidity for today & Wednesday
- scattered rains return for Thursday, then scattered-to-likely into the weekend
- watching a healthy-looking disturbance in the Atlantic

It took a little longer this morning to clear the clouds out of the Baton Rouge skies, but by mid-day things were looking mighty fine.

Our third ‘cool’ front for July? Even if this month’s frontal passages didn’t knock temperatures way down, our three July fronts delivered a nice drop in humidity levels for most of the viewing area. And while we’ve had plenty of 90° days during July (today makes 21), the fronts have contributed to a July that will wind up cooler-than-normal – uh, not that you would really notice.

And while we won’t call July fronts rare, three distinct frontal passages in July is certainly not normal. The ‘cool’ fronts pushed through metro Baton Rouge on:
- the pre-dawn hours of July 3rd, while we watched Hurricane Arthur slide up the East Coast, 
- just after midnight on the morning of July 16th, and 
- near sunrise this morning.

And technically, there was another ‘cool’ front passage on the morning of the 20th, but this was really the lingering boundary from the July 16th frontal passage which had stalled and then meandered along the coast for several days.

And by the way, we admit that we’re being a little loose with the weather terminology. Many weather purists would content that there is no such animal as a ‘cool’ front -- that they are all ‘cold’ fronts. But down here, summer ‘cold’ fronts are far from ‘cold’ -- in fact, most aren’t even ‘cool’! Yes, they generally deliver a drop in temperatures but only by a few degrees. The real delight in our summer ‘cool’ fronts is the drop in humidity that they provide, albeit rather brief in most instances. So calling it a ‘cold’ front seems a little silly along the Gulf Coast ... maybe we should call it a low-humidity front?

No, we’ll stick with ‘cool’ front -- you know what it means … and so do the purists!

Sadly, as we just mentioned, the effects of these cool fronts are usually short-lived and such will be the case this go-around. We’ll enjoy the dip in humidity through the night and into Wednesday, but by Thursday our familiar Gulf humidity will start creeping back into the viewing area. As is so common in mid-summer, today’s front won’t make it very far south, with the guidance suggesting that it will stall and meander near the coast or over the southern parishes for the next few to several days. The increasing low-level moisture will combine with daytime heating and the added lift provided by the meandering front to generate isolated to scattered, mainly-afternoon rains for Thursday, with even better rain chances for Friday and the weekend. 

In the tropics, ‘invest 93L’ seems destined to become a tropical cyclone (depression or tropical storm) in the next day or so. As of this afternoon, the National Hurricane Center (NHC) has 93L posted with a 70% chance of development in the next two days (and an 80% chance over the next five days). Satellite imagery today shows a system with decent central spin and some modest banding features. On the other hand, 93L is still dealing with some fairly persistent wind shear and suggestions of ‘dry air’ intrusion from the north. All that said, we think it likely that 93L gets a ‘number’ (tropical depression) or a ‘name’ (Bertha, a tropical storm) by sometime tomorrow given today’s trends. 

As for 93L’s destination, it is far too early to rule-out a visit to the Gulf, but almost all of the forecast guidance keeps a developing 93L in the Atlantic.

No comments:

Post a Comment