TROPICAL STORM DELTA IS FORECAST STRENGTHEN INTO A HURRICANE AND THREATEN THE GULF COAST

Tropical Storm Delta has formed in the central Caribbean Sea. Atmospheric conditions conducive for strengthening are ahead, and the National Hurricane Center is forecasting the system to intensify into Hurricane Delta and threaten the northern Gulf coast late this week.

This is the 25th named storm of this hurricane season, which comes about 6 weeks earlier than in the ultra-busy season of 2005, which was the only other time we had this many.

The forecasts for Delta have changes dramatically since yesterday. It now appears that a corridor will set up that will take the tropical storm or hurricane into the Gulf of Mexico with only a wiggle or two, and then bend it to the north toward the northern Gulf coast. Yes, again.

The slightly weird twist is that there is already a tropical storm in the Gulf – Tropical Storm Gamma. In now appears that Delta will be much stronger than Gamma, which is weakening quickly. This means that Gamma will be deflected to the south by Delta’s circulation, while Delta will only be slightly deflected toward the west or northwest when they come close.

Tropical Storm Gamma is being ripped apart by hostile upper winds as it meanders over the southern Gulf just north of Cancún. On the satellite, you can see Gamma’s low-level swirl that is completely separate from the upper parts of the storm, which have been pushed off toward Florida by the strong upper flow. That upper moisture will continue to move northeast.

Since there is very little atmospheric steering flow to move Gamma's circulation, it is subject to being pushed around by outside influences. As Delta approaches from the east, the flow around that stronger circulation should push Gamma south near or over the Mexican coast where it is forecast to lollygag for a few days unable to do much because of dry air, possible interaction with land, and the detrimental influence of nearby Delta.

Eventually, the remnants of Gamma might get absorbed by Hurricane Delta in the Gulf, becoming just a blip on Delta’s radar.

Meanwhile, the corridor set up for Tropical Storm or Hurricane Delta between Gamma and a high-pressure system over the Atlantic will bring the strengthening system into the Gulf where a large bubble of supportive atmospheric conditions is forecast to develop. As a result, Delta is forecast to intensify fairly rapidly.

In the northwest Caribbean and the southern Gulf of Mexico, the water temperatures is still very warm, so the storm will initially have plenty of energy to work with. In the northern Gulf, however, early season cold fronts have already significantly cooled the water, which hopefully will limit the strength of the system when it approaches the northern Gulf coast.

There are also pockets of dry air over the Gulf, which may also have something of a limiting effect on Delta’s strength, but that’s not guaranteed.

At this time, it doesn’t look like Gamma will stay strong enough to be very disruptive.

The bottom line is, we’re facing another hurricane threat on the northern Gulf coast late in the week. The system has just developed at this point, so remembering the admonition that weak or developing systems generally are more poorly forecast, we shouldn’t try to guess exactly were the system might make landfall at this point.

Be ready for the details of the forecast to change, but on parts of the northern Gulf coast, it’s likely that hurricane preparations are going to be necessary once again. Hurricane Watches could go up as soon as tomorrow.

Elsewhere in the Atlantic, none of the systems is expected to be a develop.