Monday, May 27, 2013

Increasing Rain Chances This Week

By Jay Grymes & Steve Caparotta

We enjoyed somewhat of a break from our usual muggy weather for part of the weekend, but humidity is quickly making a comeback and we’ll see a return of our typical late-May ‘muggies’ through the week! That will translate into warmer morning starts near 70° and less comfortable afternoons as highs top out in the upper 80°s.

Titan9 Doppler Radar has only picked up on a few spotty showers and t-storms the last couple of days, but we’re also expecting increasing rain chances this week. Rain coverage should remain pretty limited on Tuesday – less than 20% -- but better rain chances are expected the remainder of the week. We’ll put at least a 50/50 chance of wet weather in the forecast on Wednesday, with scattered, mainly afternoon showers and t-storms each day from Thursday into the weekend.

So why are we looking for increased rain chances? Believe it or not, a lot of it will have to do will a large plume of moisture originating in the western Caribbean. Clockwise flow around high pressure (the ‘Bermuda High’) in the western Atlantic will transport this source of deep tropical moisture all the way through the Gulf and into our vicinity later this week. Increased moisture, combined with temps in the upper 80°s to near 90°, should set the stage for scattered showers and t-storms for the second half of the week into the weekend.

And a final note…with the official start of Hurricane Season looming on Saturday, FEMA and NOAA have declared this week as “National Hurricane Preparedness Week”. Today’s focus is the threat of storm surge – one that we are all too familiar with here in south Louisiana.

We’re all aware of the large storm surges associated with hurricanes like Camille, Katrina, and Rita, but did you know 2012’s Isaac produced a storm surge topping 10 feet in parts of Plaquemines and St. Bernard parishes? And it also produced flooding that some had never seen in parts of St. John, St. James and Ascension parishes. This from what was ‘only’ a Category 1 hurricane. Isaac is the perfect example of why storm surge has been removed from the Saffir-Simpson scale used to rank hurricanes. The Saffir-Simpson scale was originally designed as a ‘wind’ scale and really does a poor job of conveying the storm surge threat from a given storm. While Isaac only produced Category 1 winds, it was a larger-than-average storm that was moving very slowly near and after landfall in Louisiana – two factors that led to an enhanced storm surge. So, if you live in a flood prone area, we encourage you to avoid simply thinking of storms in terms of their Saffir-Simpson categories and to pay attention to forecasts for water level rises in your area. This will give you a much better idea of potential impacts.

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