Tropical Depression Nine Dissipates

By Dr. Jeff Masters
Published: 1:45 PM GMT on October 23, 2014

Small and weak Tropical Depression Nine dissipated over Mexico's Yucatan Peninsula Wednesday night, shortly after making landfall near 8 pm EDT Wednesday October 22, 2014 on the western shore of the peninsula. Mexican radar out of Sabancuy and satellite loops show that ex-TD 9 is bringing some heavy rains to the Yucatan Peninsula, Belize, Guatemala, and the adjacent waters, and this activity will continue into the weekend. By Saturday, some of the spin associated with TD 9 may emerge over the Western Caribbean, and we should carefully watch this area on Sunday and Monday for tropical cyclone development--though none of our reliable models were predicting development in their Thursday morning runs. A trough of low pressure connected to the large Nor'easter affecting the Northeast U.S. will inject a large amount of dry air into the Western Caribbean this weekend, discouraging development, and wind shear is expected to be a rather high 15 - 25 knots, which should keep any development slow. If development does occur, Honduras, Belize, and Mexico's Yucatan Peninsula would be most at risk of receiving impacts from the storm.

Figure 1. MODIS satellite image of TD 9 in the Gulf of Mexico on Wednesday afternoon, October 22, 2014. Image credit: NASA.

Eastern Pacific disturbance may develop
An area of disturbed weather in the Eastern Pacific a few hundred miles south of the Mexico/Guatemala border may end up impacting whether or not a tropical depression can form in the Western Caribbean from ex-TD 9. The Eastern Pacific disturbance is close enough to the Western Caribbean to compete for energy and moisture, and upper-level outflow from the Eastern Pacific storm could bring high wind shear over the Western Caribbean. Our top three models for predicting tropical cyclone genesis all develop the Eastern Pacific disturbance by early next week, and in their 8 am EDT Thursday Tropical Weather Outlook, NHC gave the disturbance 2-day and 5-day odds of development of 0% and 50%, respectively. The storm will move slowly northwards, and will likely bring heavy rains to the coast of Mexico and Guatemala this weekend.

Arabian Sea disturbance may develop
In the Arabian Sea between India and Africa, an area of disturbed weather (Invest 90A) has formed, and our top models for predicting tropical cyclone genesis, the GFS and European models, have been consistently predicting in recent runs that this disturbance will develop into a significant tropical cyclone by early next week. The Joint Typhoon Warning Center gives the disturbance a low chance of developing by Friday, but notes conditions are favorable for development, with moderate wind shear of 10 - 20 knots, excellent upper-level outflow, and very warm ocean temperatures of 28 - 29°C (82 - 84°F.) The storm will head slowly northwards over the next week, and is not a threat to make landfall for at least five days.

Figure 2. MODIS satellite image of Invest 90A in the Arabian Sea on Thursday morning, October 23, 2014. Image credit: NASA.

Jeff Masters

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About The Author
Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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