No Tropical Storm Formation Expected in the Atlantic This Week

There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for forecasting tropical cyclone genesis is predicting development over the coming five days. The operational GFS model, which had been predicting all of last week that a strong tropical disturbance or tropical storm would develop over the Western Caribbean late this week, has now backed off on that forecast, though a few members of the GFS ensemble forecast are still predicting development in the Southwest Caribbean late this week. As I explained in Friday's blog post, the GFS model's forecasts of tropical development occurring in the Western Caribbean are likely bogus. Vertical wind shear will be very high over most of the tropical Atlantic this week, and there will be a large amount of dry, sinking air, making it difficult for tropical storms to form. It's a different story in the Eastern Pacific, where low wind shear and moist conditions may lead to the formation of a new tropical depression late in the week. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave a 30% chance that a tropical depression could form by Saturday, a few hundred miles south of Mexico's Pacific coast. This morning's 00Z run of the European model supports formation of a tropical depression late this week in the Eastern Pacific.


Figure 1. Predicted vertical wind shear between the 850 mb and 200 mb levels for 8 am EDT Friday, June 20, 2014, as predicted by the 00Z Monday, June 16, 2014 run of the European model. High wind shear is predicted for most of the tropical Atlantic, thanks to the presence of strong upper-level winds from the subtropical jet stream. The region marked "Low Shear" in the Eastern Pacific has been given a 30% chance of spawning a tropical depression by Saturday in NHC's 8 am EDT Monday Tropical Weather Outlook.

Jeff Masters