A Tropical Storm Warning is up for Mexico’s Yucatan Peninsula for the expected arrival on Saturday of Tropical Depression 25, which formed at 11 a.m. EDT Friday in the western Caribbean. Poised to strengthen into Tropical Storm Gamma by Saturday morning, TD 25 is a heavy rain threat to Mexico’s Yucatan Peninsula, Belize, and western Cuba. It poses no threat to the U.S. over the next five days.

Conditions for development of TD 25 are favorable through Saturday, with sea surface temperatures (SSTs) of 30 – 30.5 degrees Celsius (86 – 87°F), light wind shear less than 10 knots, and a moist atmosphere with a mid-level relative humidity of 80%. Satellite images showed that TD 25’s heavy thunderstorm activity was steadily increasing in intensity, areal coverage, and organization as the system moved northwest at about 9 mph. An Air Force hurricane hunter aircraft is to investigate TD 25 on Friday afternoon.

Forecast for TD 25

The ridge of high pressure steering TD 25 should keep it moving to the northwest or north-northwest through Sunday, a track on which all of the major computer models agree. This motion should bring TD 25 to the coast of Mexico’s Yucatan Peninsula on Saturday, though it is possible the system could slide just north of Cancun and pass through the Yucatan Channel between Cuba and Mexico. TD 25’s forward motion is expected to slow to less than 5 mph Saturday through Monday, resulting in very heavy rains.

The track of TD 25 next week is unclear, as it will be embedded in a region of weak steering currents. The current model consensus is that TD 25 will be a relatively weak storm steered slowly westwards by the low-level winds. If TD 25 manages to over-achieve and intensify into a hurricane over the weekend, a more northerly path and a potential threat to the U.S. could materialize.

Further complications on predicting TD 25’s track may arise next week as another tropical wave, now moving through the eastern Caribbean, arrives in the western Caribbean. In an 8 a.m. EDT Friday Tropical Weather Outlook, the National Hurricane Center gave this second tropical wave two-day and five-day odds of development of 0% and 30%, respectively.

Conditions for development of TD 25 will become more hostile on Sunday, when the system will encounter a large trough of low pressure extending from Mexico into the southeastern U.S., associated with a cold front that moved through the Gulf of Mexico early this week. This trough will bring high wind shear of 20 – 30 knots to TD 25 Saturday night through Monday. In addition, plenty of dry air over the Gulf of Mexico will interfere with development, as will land interaction with the Yucatan Peninsula.

Because of these obstacles, the models do not indicate that TD 25 will achieve hurricane strength over the next five days. Beyond five days, wind shear is likely to decrease and dry air will lessen, as the cold front and associated trough over the Gulf of Mexico weaken. These factors may allow TD 25 to intensify beyond the next five days.

Heavy rains possible in Florida

The trough of low pressure that TD 25 will encounter this weekend will also act to shunt tropical moisture from the system to the northeast over Florida. This is a favorable setup for what is referred to as a potential Predecessor Rain Event (PRE), which could bring heavy rain and flooding to parts of central Florida. The experimental HAFS model (Figure 2) is predicting more than five inches of rain over a five-day period for central Florida.

Impressive category 4 Hurricane Marie churns in the northeast Pacific

In the northeast Pacific, over 1,000 miles west-southwest of Mexico’s Baja Peninsula, Hurricane Marie vaulted to category 4 status with 130 mph winds and a 948 mb central pressure at 11 a.m. EDT Friday morning.

Also see: Extreme events ‘presage worse to come’ in a warming climate

This intensity ties Marie with Hurricane Douglas of July and Hurricane Genevieve of August as the basin’s most intense hurricane of 2020. Marie still has a window of opportunity to intensify into a stronger storm on Friday before crossing into a region of cooler ocean temperatures and higher wind shear that will likely induce significant weakening beginning on Saturday. Marie is not a threat to any land areas.

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Posted on October 2, 2020 (1:27pm EDT).