Friday, August 9, 2013

Sct'd T-Storms Persist into the Weekend

By Jay Grymes & Steve Caparotta

As expected, the upper-level ridge that has been the driver in our run of dry, mid-90° days has continued to weaken and shrink, being squeezed on the south side by a west-bound tropical wave crossing the Gulf and on the north by a moderately-well developed upper-level trough.
Scattered rains extended over the viewing area today, with rains being a bit more numerous closer to the coast.  The combination of the weakened ridging, the Gulf wave and an increase in atmospheric moisture over the region prompted today’s rains ... and we’re keeping rain chances in the “scattered” category for WAFB neighborhoods through the weekend.

Of course, another advantage of the rain -- which typically means more cloud cover -- is a dip in the daytime highs.  That’s why, like today, we anticipate highs for Saturday and Sunday to top-out in the low 90°s.  Yep -- still summer-like for South Louisiana, but at least a little cooler than what we experienced through the first 8 days of August.

Plan on morning starts for Saturday and Sunday in the mid 70°s for the BR metro area ... and as usual, a little warmer closer to the coast and a tad cooler near the state line.  Mornings will be dry for most, but those closer to the coast should expect a few AM showers.  By the afternoon for both days, our moist-and-unstable summer air mass will get a sufficient boost from daytime heating to kick-off afternoon showers and t-storms.

We aren’t anticipating all-day rains for either weekend day and no severe weather outbreaks.  In fact, not everybody in the viewing area gets “wet” this weekend -- but between the two days, most WAFB communities can expect at least some rain.  Guidance from the NWS Weather Prediction Center indicates that most WAFB viewers should plan on around 0.25” to 0.75” of rain over the weekend, with localized totals of 1.0” or more where slow-moving storms produce heavier downpours.

We can use the rain.  Most of the viewing area has been quite dry over the past couple of weeks.  In fact, Doppler radar estimates suggest that many sections of the WAFB region, especially areas east of the Amite River, are running roughly 50% to 75% of normal for rainfall for the past 30 days.  That’s not yet “drought” conditions but most of us won’t complain about a good soaking.  In fact, even with our forecast for “scattered rains” this weekend, anything less than a half-inch will only provide brief, limited relief from the hear -- at this time of year, evaporation rates typically run around a quarter-inch per day.

We’re getting some mixed signals about an approaching cool front towards the middle of next week.  Could it make it this far south and provide some real relief from the heat?  Well, it is possible, but don’t count on it.  For now, we’ll go with a forecast that stalls either over us or just to our north.  That means plan on staying warm and humid  with “scattered” rains just about every day through the upcoming work week.

Still “quiet” in the tropics ... and likely to remain so well into next week at least.  But remember, the peak of the season (roughly September 10th) is not far off -- are you ready?

In the meantime ... try to stay cool and enjoy the weekend!

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