Near-record Gulf warmth may help fuel late week system

So far this summer, the Gulf of Mexico has been exceptionally warm.

Overall, the surface waters across the Gulf this July are running warmer than any other year in the past 41 years (since the collection of continuous satellite data), except for 2016.

This is especially impressive considering how warm 2016 was relative to other years in the record books.

The pattern of warmth across the Gulf is also strikingly similar between this year and 2016, with the highest concentration of above average temperatures situated along the north-central and northeastern Gulf.

Water temperatures off Grand Isle, the small fishing town along the southeastern Louisiana coast, reached nearly 92 degrees late Sunday afternoon.

High fidelity readings (every six minutes) of water temperature extend back 25 years at this station. Sunday’s reading was among the highest recorded for any month at Grand Isle (in the 99th percentile), including August, when water temperatures typically top out.

The concern with such warmth, especially along the northern Gulf, is not only fuel for would-be hurricanes, but also a rich source of moisture for even those less severe storm systems.

In August 2016, an unnamed disturbance with tropical characteristics produced catastrophic flooding across southern Louisiana, dropping up to 30 inches of rain centered near Baton Rouge over a three-day period, causing nearly $10 billion in damage and killing over a dozen people.

There’s little doubt the record-setting water temperatures over the northern Gulf during the summer of 2016 were a contributing factor to the heavy rains that fell during the event.

This week, we’re monitoring another potential rainmaker along the northern Gulf coast.

A dying cold front that stalled out across the southeast U.S. is draped from the Florida panhandle to south Louisiana.

Pressures are gradually falling in this area and the National Hurricane Center is indicating the possibility of some tropical development later in the week with the system.

The big question with potential development is how much of the system remains offshore over the very warm waters of the northern Gulf by the latter half of the week.

The system will be stuck in an atmospheric no-man’s land between two areas of high pressure – one to the east, another to the west – which should keep it drifting all week along the north-central Gulf.

The slow movement and configuration of upper-level winds near the low-pressure area will support abundant rainfall from south Louisiana to the Florida panhandle from mid-late week into the weekend.

The National Weather Service is already indicating the likelihood of excessive rainfall for this area from Thursday through Saturday.

While we’ll keep an eye on development, the biggest threat regardless will be heavy rainfall in the coming days for our friends along the northern Gulf coast.

Otherwise, a significant dust outbreak moving through the deep tropical Atlantic will keep things quiet, with no tropical threats expected this week for South Florida.