Thursday, June 19, 2014

Hot, Iso'd T-Storms...You Know the Drill

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- plan on more of the same summer “sultries” right through Sunday
- summer officially begins on Saturday morning (at 5:51am CDT)
- hit-n-miss afternoon thundershowers for Friday & the weekend

Our high today at Metro Airport of 93° is the highest reading of the year thus far. But we are almost certain to top that in the coming weeks.

We’ll keep this short since the forecast reads the same as it has for most of the week. To summarize, the outlook for Friday and the weekend looks like this:
- morning lows in the low 70°s for most of us with patchy, mainly-light fog near sunrise,
- afternoon highs running in the low 90°s with peak Heat Index readings in the mid to upper 90°s, and
- afternoon rain chances running around 20% to 30% each day.

The upper-level ridge that has kept a modest ‘lid’ on our afternoon t-shower development remains in play, but it continues to slowly weaken. We still think that it will continue to hamper the onset of afternoon rains but may ‘soften-up’ just enough to allow a very slight increase in rain coverage over the weekend. So let’s call it a 20% rain chance for Friday and Saturday and then at about 30% for Sunday -- which means most WAFB neighborhoods remain dry each day.

Here’s a little ‘math’ game if you are into raw statistics. If we assume that chances-of-rain for your yard are 20% for both Friday and Saturday and then 30% for Sunday, what are the chances that you go all three days without any measurable rain? If you’ve never contemplated this one, the purely ‘mathematical’ solution is not as simple as you might first think.

The answer is: [(1 - 0.2) x (1 - 0.2) x (1 - 0.3)] = [(0.8) x (0.8) x (0.7)] = 0.448

. . . roughly a 45% chance (44.8%) that you go through Friday, Saturday and Sunday without getting any rain at all. In other words, even with our relatively low day-to-day rain percentages, there is better than a 50-50 chance you’ll get at least one sprinkle sometime over the next three days. And even with those low percentages, a few of you will see rain on two or more days.

And remember that the “chance of rain” does not translate into a forecast for an “amount of rain.” Just like we’ve seen the past several days, although the majority of WAFB neighborhoods have remained dry each afternoon, a someone has gotten something each afternoon. And one or two of those neighborhoods have experienced significant downpours. The truth is, forecasting exactly where it will rain in the summer is almost impossible ... and how much it will rain at any one place is just as difficult!

Here’s some good news: it remains quiet in the tropics and is expected to stay that way through the next several days, at least.

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