Tropical Depression 31 Forms In The Caribbean Sea

Another tropical cyclone has formed in the Atlantic basin, Tropical Depression Thirty-One, forecast to become the Atlantic next hurricane, possibly making a run at major hurricane status early next week.

Tropical Depression Thirty-One is forecast to become a named storm later today, continuing 2020’s record-breaking pace with already 29 named storms, the most in Atlantic history. With the formation of Tropical Depression Thirty-One, 2020 has now tied 2005 for the most number of systems (31) at tropical depression strength.

When this system is named later today, it will become 2020’s 30th named storm and will be called Iota, the first time this name will be used operationally in Atlantic history.

Iota is forecast to be a major blow to Nicaragua, Honduras, and Guatemala, still recovering from the devastating impact of Eta just last weekend. Rainfall totals between 20 to 30 inches are possible. This rainfall would lead to significant, life-threatening flash flooding and river flooding, along with landslides in areas of higher terrain.

This tropical cyclone is not forecast to directly impact Trinidad, Tobago, or the Lesser Antilles as it moves generally eastward.

List of names for the 2020 Atlantic Hurricane Season. The next named tropical cyclone will be called Iota.

At 11:00 AM AST, the center of Tropical Depression Thirty-One was located near latitude 14.2 North, longitude 74.3 West. The depression is moving toward the west-southwest near 7 mph (11 km/h) and this motion is expected to continue through early Saturday. A westward to west-northwestward motion at a slightly faster forward speed is expected to begin by late Saturday and continue through early Monday. On the forecast track, the system will move across the central Caribbean Sea during the next day or so, and approach the coasts of Nicaragua and northeastern Honduras late Sunday and Monday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. The depression is forecast to strengthen into a tropical storm later today or tonight. Additional strengthening is likely over the weekend, and the system could be near major hurricane strength when it approaches Central America. The estimated minimum central pressure is 1007 millibars.

Tropical Depression Thirty-One Forecast Track as of 11:00 AM AST Friday 13th November 2020. (National Hurricane Center)

Watches & Warnings

Tropical Depression Thirty-One Watches and Warnings as of 11:00 AM AST Friday 13th November 2020. (National Hurricane Center)

There are no coastal watches or warning in effect.

Interests in Nicaragua and Honduras should monitor the progress of this system. A Hurricane Watch may be required for a portion of that area tonight.

Hazards Affecting Land

Tropical Depression Thirty-One probabilities for tropical-storm-force winds as of 11:00 AM AST Friday 13th November 2020, as well as the most likely time of arrival of tropical-storm-force winds. (National Hurricane Center)

Rainfall: Through Wednesday morning, Tropical Depression Thirty-One is expected to produce 4 to 8 inches of rain, with local 12-inch totals, across portions of northern Columbia, Panama, and Costa Rica.

Across Jamaica and southern Haiti, 2 to 4 inches are expected, with local amounts up to 6 inches.

Across the remaining sections of Central America, the system has the potential to produce 20 to 30 inches of rain with a focus across northern Nicaragua and Honduras. This rainfall would lead to significant, life-threatening flash flooding and river flooding, along with landslides in areas of higher terrain.

This system is of no direct threat to the Windward Islands, including Trinidad and Tobago.

Tropical Depression Thirty-One Forecast Discussion

Tropical Depression Thirty-One (Weathernerds.org)

eep convection associated with the area of low pressure over the central Caribbean Sea has increased and become more concentrated since yesterday. One-minute GOES-16 visible satellite imagery shows that the circulation has also become better defined, with a westerly component seen in the low-cloud motion near the southwestern edge of the primary convective mass. Subjective Dvorak intensity estimates from both TAFB and SAB are T2.0, indicating that the convection has become sufficiently organized for the system to be classified as a tropical depression. The initial wind speed is set at 30 kt, in line with the Dvorak classifications.

Environmental conditions of low vertical wind shear, warm sea surface temperatures, and a moist atmosphere favor intensification over the next few days. Given the current broad and sprawling structure of the system, strengthening may begin as gradual today, but once an inner core organizes, steady-to-rapid strengthening appears likely. While the SHIPS rapid intensification index does not show very high chances of rapid strengthening for any one 24-h period over the next few days, it does indicate a 50/50 chance (nearly 10 times the climatological mean) of a 65-kt increase in wind speed over the next 72 hours. As a result, the NHC forecast calls for significant strengthening during the 24 to 72 hour time period, and the system could approach the coast of Central America as a major hurricane in a few days. The NHC track forecast at days 4 and 5 shows the system weakening over land, however, some of the track guidance keeps the system just off the coast of Honduras at that time. If a more northern track occurs, the system could be stronger at 96 and 120 h if it remains over water.

The depression is moving west-southwestward at about 6 kt. A strong mid-level ridge that lies over Florida and the western Atlantic should steer the cyclone west-southwestward during the next 12 to 24 hours. After that time, the ridge is forecast to begin sliding eastward, and a westward to west-northwestward motion should begin. On the forecast track, the cyclone is expected to approach the coast of Central America in 60-72 h. The track guidance is in good agreement through the first couple of days, but there is increasing cross-track spread after that time. The HMON, HWRF, and GFS show a track near or north of the coast of Honduras after 72 hours, while the ECMWF and UKMET are farther south. For now, the NHC track is near the middle of the guidance envelope between the HFIP corrected consensus model and the TCVA multi-model consensus.

Key Messages:

  1. The depression is expected to strengthen to a hurricane while it approaches the coast of Central America, and there is a risk of dangerous wind, storm surge, and rainfall impacts across portions of Nicaragua and Honduras beginning Sunday night. Hurricane Watches will likely be issued for a portion of this area tonight.
  2. Through Wednesday morning, heavy rainfall from Tropical Depression Thirty-One may lead to life-threatening flash flooding and river flooding across portions of Haiti, Jamaica and Central America. Flooding and landslides from heavy rainfall could be significant across Central America given recovery efforts underway after Hurricane Eta.

Forecast discussion by NHC Forecaster Brown.

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