Tricky Track Forecast Ahead for Tammy

Short-lived Tropical Depression 21 forms, moves inland over Central America

Tammy forecast track models through Sunday, October 29, 2023, with the European model in yellow, American GFS in green, and consensus model in bold red.

Tammy is hanging on as a borderline hurricane this morning – albeit with an increasingly disheveled appearance – as it churns over the western Atlantic some 400 miles north of the Caribbean islands.

Forecast models continue to show a fork in the road for Tammy by mid-week, with some models flinging the storm system northeastward and out to sea while others insist a weaker system will bend westward or even southwestward into the weekend.

Forecast models, including all ensemble members, for Tammy through early next week. Some models suggest Tammy will accelerate northeast and out to sea, while others suggest its remnants will slide west or even southwest into the weekend. Forecast scenarios toward Florida and the U.S. are much weaker or non-tropical in nature, so for now we are not concerned about a serious threat from Tammy, even if extreme southern scenarios come to pass. Credit: Tomer Burg/University of Oklahoma

The tricky track has the most immediate implications for Bermuda, where a westward path would bring the possibility of tropical storm conditions by the weekend.

The big steering factor is a jet stream dip approaching from the west which will help direct Tammy northward over the next few days. By late week, models are split on whether the jet stream flow will continue to guide Tammy out to sea or whether the jet stream will bypass the storm, which could trap it under high pressure steering to the west, diverting its course back to the west or even southwest.

If a westward or extreme southwestward scenario occurs, it’s important to know Tammy would be a much weaker low-pressure system and likely no longer tropical. So the model plots pointing to Florida do not suggest a serious tropical threat from Tammy for the time being. Regardless of the track outcome, Tammy is not currently a concern for us in South Florida.

The official forecast calls for Tammy to become post tropical as it begins to bend west by late week. Though the structure of the storm will resemble a wintertime low pressure, strong winds above tropical storm strength will continue with the system into the weekend.

Quick hitting Tropical Depression 21 moves inland over Central America

Tuesday morning satellite of Tropical Depression 21 (center location denoted by the red “L”). Credit: NOAA

Invest 95L got the upgrade to Tropical Depression 21 on Monday afternoon before moving inland over Nicaragua. The short-lived depression is weakening as it moves toward Honduras, but continues to bring heavy rain – up to a foot in spots – to Nicaragua and parts of southern and eastern Honduras. Flash flooding and the possibility of mudslides in higher terrain are the primary threats from the system over the next few days.

Looking ahead to next week

Long range models continue to advertise lower pressures over the central Caribbean or western Atlantic into early next week in the wake of Tammy. For now, we’re not seeing anything definitive, but we’ll keep an eye to this area for any mischief. The good news for us in Florida is that by mid-week, jet stream winds should pick up considerably, which would offer protection against anything tropical in our neck of the woods.