Tuesday, September 17, 2013

Gradually Increasing Rain Chances

By Jay Grymes & Steve Caparotta

Hot and mainly-dry was the forecast for today, and that’s what most of us got. Yes there were a few showers and flashes of lightning mainly south of metro BR, but for most of us the weather story today was the heat, with highs in the low to mid 90°s.

With daytime temps in the 90°s, low-level Gulf moisture in place, plus a weak quasi-stationary front over the Gulf Coast states, why not more widespread rain today? Because, like yesterday, a mid/upper-level ridge centered near the TX/LA border kept a fairly solid lid on the atmosphere, allowing only spotty showers, at best, to develop during the afternoon.

The weak front currently over our area will dissolve over the next 24 hours. More importantly, the upper-air ridge will slowly weaken and shift to the southeast over the next few days, taking the atmosphere’s cap with it. By week’s end, the current Gulf Coast ridge will have been replaced by an upper-level trough and a surface front. All this adds up to a slow-but-steady rise in rain chances through the work week, culminating in a “rain likely” forecast with our next cold front on Saturday.

Most of us need the rain, but many of us may be disappointed with the Saturday outlook. The current NWS Weather Prediction Center (WPC) forecast has a cold front entering NW Louisiana early Saturday but then only slowly moving southward. The WPC forecast charts keep the front over Louisiana through Sunday into early Monday before finally pushing out to the Gulf.

That scenario looks rather wet for Saturday afternoon, when LSU takes on Auburn in Death Valley, and suggests decent rain chances continuing into Sunday, at least. So, “It never rains in Tiger Stadium.” -- looks like we’ll put that legend to the test.

But then, as we noted, we can use the rain. In addition, we should get a run of days where highs fail to reach the 90°s.

In the tropics ... interaction with the mountains of central Mexico finished-off INGRID’s central core and the National Hurricane Center (NHC) posted the final advisory for ‘her’ this morning at 4AM. Still, INGRID’s remnants continue to dump heavy rains over portions of east-central Mexico, where life-threatening flooding continues.

Even with the strong shear pushing the main convection well east and northeast of the low-level center, the NHC still considers HUMBERTO to be a minimal tropical storm as of 4PM. And the NHC is still holding to their expectations for some modest strengthening over the next couple of days although the outlook no longer calls for a return to hurricane intensity. Regardless, HUMBERTO is expected to lose ‘his’ tropical character by the end of the week and is no threat to any land areas.

The mess in the western Caribbean and extending into Belize and the Yucatan appears to be getting its act together. Late last night we showed a surge in convection just off the coast of Belize -- while there is no clear low-level core, computer models are coming together on the future of this broad low, taking it across the Yucatan and into the Bay of Campeche by late tonight or tomorrow.

As we’ve seen with this season’s BARRY, FERNAND and INGRID, conditions in the SW Gulf have been favorable for slow, limited development.

Guidance is suggesting that this low could become JERRY in the next few days, and unlike the last few systems in this part of the Gulf, it may not continue westward into Mexico. A stalling system later this week could feel a tug to the north or northeast from the anticipated trough over the eastern U.S. into the weekend.

No comments:

Post a Comment