| Above: Water vapor satellite image of the tropical Atlantic taken at 8:15 am EDT Tuesday, July 11, 2017. Large swaths of dry air (brown and black colors) dominated the Atlantic. The remains of Ex-TD 4 and an African tropical wave (which we were following on Monday) were less organized becasue of the dry air. Image credit: NOAA. |
Dry air rules in the tropical Atlantic, where the two threat areas we were concerned about on Monday have weakened considerably, and now pose little threat of development. Satellite images show that the remnants of Tropical Depression 4, located several hundred miles east of the Bahamas, continue to kick off a modest area of disorganized heavy thunderstorms, as the system interacts with an upper-level trough of low pressure. The air is very dry around ex-TD 4, with a relative humidity near 45%, and this dry air should prevent much development. The 0Z Tuesday operational runs of our three top models for predicting tropical cyclone genesis, the GFS, European and UKMET models, did not show regeneration of ex-TD 4, and there was little support for development among the various model ensemble members.
The tropical wave located a few hundred miles southwest of the Cabo Verde Islands that we were watching yesterday--and which had considerable support for development from the GFS model--is now almost devoid of heavy thunderstorms. This wave had little support for development from the 0Z Tuesday computer models, and the models are not showing much action in the Atlantic over the next ten days. The Madden-Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, and which can increase the odds of tropical cyclone formation when it is strong and located in the proper location, is currently weak, and will not favor tropical cyclone formation in the Atlantic over the next week or two.
Eugene weakening, but generating high surf
Hurricane Eugene peaked on Sunday afternoon as the Eastern Pacific’s first major hurricane of 2017, but is now below hurricane strength after encountering cooler ocean waters of 24°C (75°F) and a drier, more stable atmosphere, a few hundred miles west of Mexico’s Baja Peninsula. As of 5 AM EDT Tuesday, Eugene had top winds of 65 mph, and was expected to dissipate by Wednesday night. Eugene is kicking up some large swells, and a High Surf Advisory is up for the Southern California coast, with waves of 4 – 8 feet expected Tuesday afternoon through Wednesday.
