Recent runs of the GFS and European model have been consistently predicting that an area of low pressure capable of developing into a tropical storm will form late this week over the southwestern Caribbean Sea, off the coast of Costa Rica. Conditions for development will be favorable, with moderate wind shear of 10 – 20 knots, warm sea surface temperatures of 29 degrees Celsius (84°F), and a moist atmosphere. Steering currents favor a westerly to west-southwesterly motion at 5-10 mph, putting Costa Rica and southern Nicaragua at greatest risk of experiencing a landfall.
None of the 51 members of the 0Z Monday run of the European model ensemble and fewer than 20% of the 31 members of the 6Z GFS model ensemble members, predicted a more northerly track, with a threat to northern Nicaragua. In multiple recent runs, the GFS model has been predicting that this disturbance will develop into a tropical storm by Friday, make landfall as a tropical storm near the Costa Rica/Nicaragua border on Saturday, then cross into the Eastern Pacific Ocean and reorganize, bringing heavy rains to the Pacific coast of Central America early next week. The next name on the Atlantic list of storms is Kappa, the 10th letter of the Greek alphabet. The storm would likely keep the name Kappa after crossing in the Northeast Pacific and reorganizing into a tropical storm (if it were still identifiably the same cyclone).
If Kappa does form as the GFS model has been predicting, the storm is unlikely to have sufficient time over water to develop into a hurricane, and it would be a relatively small tropical storm. However, Kappa would be a significant heavy rain threat for southern Nicaragua, Costa Rica, and Panama, with 5-10 inches of rain possible Friday through Sunday. As of Monday afternoon EST, it does not appear that this potential future storm would be a heavy rain threat for the areas of northern Nicaragua and Honduras facing devastation from by Hurricane Iota, although broader easterly flow across the region may continue to keep intermittent rains over the Iota-affected region for a number of days.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...40 percent.