21 August 2020

Laura and TD14 both aiming for Gulf of Mexico at the same time

Tropical Depression 13 was upgraded to Tropical Storm Laura on Friday morning. This is the season's 12th named storm; the previous record earliest date for the "L" storm was August 29th (Luis in 1995).  Over the past fifty years, the average date of the 12th named storm formation is November 26th: the end of the season.

The tropical storm has peak sustained winds of 45 mph and it's moving toward the west at 18 mph. It will pass over/near the northern Windward Islands later today, Puerto Rico on Saturday morning, and Hispaniola on Saturday night. The tropical storm watches and warnings as of Friday morning are shown below, along with the "cone of uncertainty". Aside from land potentially keeping it weak, it does still have dry air and wind shear to contend with in the near future. The intensity forecast in the Gulf of Mexico comes with a LOT of uncertainty. The global models barely maintain it as a depression in a few days.

During the past day, the model guidance has generally shifted southward, and weaker. In stark contrast to what I wrote in yesterday's post, there is now no model guidance indicating a major hurricane landfall in southeast Florida. Additionally, the majority of the tracks remain just south of Florida. This also increases the probability of land interaction with the Greater Antilles which could actually be its demise. If it survives the next couple of days, it will enter the Gulf of Mexico and be freer to intensify.

Southeast Florida should still be cautiously monitoring for potential impacts on Monday. While a tropical storm or hurricane looks unlikely right now, it cannot be ruled out just yet, and you wouldn't want to be caught completely unprepared if the unlikely scenario is realized.

Tropical Depression 14 is close to becoming Tropical Storm Marco, which will be the record earliest 13th named storm... the current record is September 2. It is located just north of Honduras and is forecast to track toward the northwest for the next several days. This trajectory brings it into the Gulf of Mexico on Sunday morning... Laura is expected to enter the Gulf of Mexico on Monday morning, so it might get crowded.

It is entirely possible that Laura could make landfall along the northern Gulf coast on Tuesday morning, then Marco could make landfall slightly further west on Tuesday morning. They could both be hurricanes at landfall, both be tropical storms, both be tropical depressions, or some mix.  Regardless, it's quite rare, and as they get closer, the low pressures could interact with each other, orbiting around a common center, in a dance known as the Fujiwhara effect.  This wouldn't have an effect on their impacts, but just introduce subtle nudges in each of their tracks.

What we can say this far out is the entire Gulf coast should be closely watching both systems, and preparing for some threat of heavy rain and storm surge over a wide area.

1 comment:

  1. Thank you for this posting, just breathed a sigh of relief but will keep watching