Outlook is for drier than average fall

Published 7:00 am Tuesday, September 26, 2017

By Skip Rigney

Three of the last four months have been wetter than average in Pearl River County, but it looks like we are heading into a drier-than-average autumn.

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Rain gauges across the county collected above average amounts during May, June, and August. Many locations received over twice the average amount of rainfall during those months.

This summer only July was drier than average in most of the county. The exceptions were the northernmost parts of the county, for example near Hillsdale and Ford’s Creek, which had a wetter-than-average July.

Typically, autumn is our driest season of the year. Forecasters expect this fall to be especially dry.

The average precipitation in Pearl River Country ranges from four to five inches each month during September, October, and November.

For comparison, our wettest months tend to be December through March, and June through August, all of which average between five and six and one-half inches.

This September most locations in the county have received only one-half to two inches of rain, which is ten to fifty percent of the long-term average total for September.

Some of this month’s rain occurred over this past weekend and yesterday. This included Saturday evening, September 23rd, when a severe thunderstorm rumbled across the county bringing rain, dangerous lightning, and gusty winds.

The cause for the showers has been low pressure slowly swirling counterclockwise three to seven miles above the central Gulf Coast.

Today, that low is weakening. After a few widely scattered thundershowers this afternoon and evening, our chances of making up any more of our September rainfall deficit will sharply decrease for the rest of the week.

Wednesday and Thursday look to be very warm late summer days with highs in the lower 90s.

A weak cool front will move southward through our area on Thursday. Normally, a frontal passage means an increased chance of showers, but this week the air will begin drying out ahead of the front, so no rain is expected.

Thursday’s cool front will be followed by a stronger, reinforcing shot of cooler, dry air from Canada on Saturday.

Friday through Monday expect cooler early morning lows in the lower to middle 60s. Temperatures will rise into the upper 80s on Friday, but only reach the middle 80s mid-afternoon on Saturday, Sunday, and Monday.

A slight chance of showers may return Sunday afternoon as Gulf humidity slowly returns.

The long-term outlook from the National Climate Prediction Center (CPC) is that our rainfall this October will likely be even less than what we usually receive in that typically dry month.

CPC also indicates that the entire period from October through December this year has a better than even chance of being drier than average.

That expectation is reflected in the Seasonal Drought Outlook issued by the CPC last week in which they said that drought development is likely over the next three months over most of Mississippi and southeastern Louisiana.  One reason for the dry outlook is that the CPC expects a cooler-than-average sea surface temperature pattern to take hold in the tropical east Pacific. Such a pattern is known as La Nina (the opposite of an El Nino), and the associated large-scale atmospheric patterns usually result in drier conditions along the U.S. Gulf Coast.