Increasing Chance For Tropical Cyclone Development In Gulf Of Mexico This Week

There’s an increasing chance for tropical development in the Gulf of Mexico by mid-to late this upcoming week. A shortwave is currently located over the Tennessee Valley (see Fig. 1). This shortwave will continue to advance southeast today into Monday (see Fig. 2). As the shortwave dives southeast, a weak surface low will develop over the northeastern Gulf of Mexico. This is when the processes of tropical development become possible. The National Hurricane Center (NHC) has given this system a 40% chance of tropical development over the next five days (see Fig. 3). The EPS is also on board with tropical cyclone development in the northeastern Gulf of Mexico with probabilities of 90% (see Fig. 4).

Fig. 1: Current location of shortwave

Fig. 2: Shortwave location on Monday (tomorrow)

Fig. 3: NHC probabilities of tropical development over the next five days

Fig. 4: EPS tropical cyclone development probabilities

The low will meander over the northeastern & northern Gulf of Mexico through mid-week before moving west & eventually north. The steering flow is pretty relaxed, which will allow the low to “hangout” over the northern Gulf of Mexico through the end of the upcoming week. The slow movement of the low should allow for the low to begin to obtain tropical characteristics and intensify. By late Wednesday, the low should be located over the northeastern Gulf of Mexico; somewhere just south of the Florida Panhandle according to the Euro (see Fig. 5). At this point, the low should begin to increase in intensity.

Fig. 5: Low’s location late Wednesday

The low, after meandering and slowly moving west, should begin to move north by late week into the weekend. Guidance is indicating a landfall by late Friday into Saturday. The Euro is suggesting the low will gain tropical characteristics and move inland along the Mississippi coast as a Tropical Storm late on Saturday (see Fig. 6).

Fig. 6: Location of the possible tropical storm by late Saturday

While numerical guidance is beginning to get on board with the development of the low and slow intensification over the northern Gulf of Mexico, there are some significant differences in output. The Euro is suggesting a stronger and farther west solution than the GFS. The GFS meanders the low across the northeastern Gulf of Mexico before making landfall late Friday as a weak surface low. The Euro is much stronger and farther west, and has landfall late Saturday.

One thing is evident in the guidance. The low (or tropical storm) will be rather lopsided. The eastern side of the system would have an interaction with the Bermuda high, which would cause rapidly rising air, pull in rich & deep moisture and increase the pressure gradient. This would allow for the majority of the impacts to be realized on the eastern side of the low. Regardless of tropical development, heavy rain is likely this upcoming week along the Gulf Coast. From Florida to Louisiana, coastal areas will see 4-10″ of rain (see Fig. 7). It should be noted, the heavy rain will move inland by the weekend across the Southeast, which is not well depicted on Fig. 7.

Fig. 7: WPC’s 7-Day rainfall forecast

Forecasting the development & track of a tropical cyclone before it has developed is extremely difficult. It is possible this disturbance will not acquire tropical characteristics and possible the Euro is over intensifying this low (the Euro is by far the strongest & farthest west but the Euro has handled the shortwave well thus far and has a history of forecasting tropical cyclogenesis well). Regardless of tropical development, extremely heavy rain is likely for parts of the Gulf States. If this system becomes tropical in nature, Barry will be the designated name. Everyone from east Texas to Florida should keep abreast to the forecast this week.