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Why no rain? Saharan dust moves off African coast into the Atlantic

A dusty example of the Saharan Air Layer
A dusty example of the Saharan Air Layer

You’ve seen our forecast for the week ahead and there are a lot of big suns on it without much rain! In fact, the European and American models keep flip-flopping on rain toward the end of this week or the weekend. The American even brings a June front through here on June 24th! Wouldn’t that be something?

June Front?
June Front?

That is way out there, so don’t get excited about it, but it may well be our next best chance for rain. Why? The Saharan Air Layer (SAL) is dust from the Sahara Desert. As that desert heats up in the summer, the dusty air rises into the atmosphere and moves off the African coast into the Atlantic where it can be transported all the way here. The current SAL looks like this and while a lot of those red/orange colors depict just dry air, I have noted the pink -- that’s the dust:

The SAL coming off Africa.
The SAL coming off Africa.

And the forecast through next week is for a series of high-pressure systems over the Gulf and Atlantic to act as a conveyor belt, steering the dust into Texas through the June 19-21 period:

High Pressure with clockwise winds brings the dust through the Caribbean to the Gulf and into Texas
High Pressure with clockwise winds brings the dust through the Caribbean to the Gulf and into Texas

We need rising air to get clouds and rain and right now a strong high-pressure ridge over us is prohibiting that because a high produces sinking air. Factor in a dusty forecast into the next weekend and I don’t expect much rain. It’s possible enough shallow moisture (humidity) rises for a sea breeze shower, but it will have to contend with the SAL.

In the meantime, no complaints about the wonderful weather right now! Patio perfection for mornings and evenings.

Frank

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