Little Change to 94L; Hawaii Watching Guillermo; TC 2 Kills 27 in Myanmar/Bangladesh

A strong tropical wave that pushed off the coast of Africa on Wednesday (Invest 94L) was located a few hundred miles southwest of the Cape Verde Islands on Thursday morning, and was headed west at 15 mph. 94L does have conditions that favor some slow development over the next few days. Satellite images show that 94L has a decent amount of spin, but only a modest area of heavy thunderstorms that have not increased in organization this morning. Wind shear off the coast of Africa is moderate, 10 - 20 knots, ocean temperatures are a warm 28°C, and the atmosphere is reasonably moist. The 8 am Thursday run of the SHIPS model predicted that wind shear would remain moderate over 94L for the next five days, but ocean temperatures beneath it would cool to 26°C by Sunday, at which time 94L will encounter an increasingly dry and stable airmass courtesy of the Saharan AIr Layer (SAL). The SAL is dominating most of the tropical Atlantic, from the coast of Africa into the Central Caribbean, making 94L's long-term survival questionable. If 94L does manage to make it to the Caribbean, the high wind shear that has dominated the region all summer will likely tear the storm apart. The Thursday morning ensemble runs of the GFS and European models--done by running the models at lower resolution and varying the initial atmospheric conditions slightly to generate an "ensemble" of twenty potential weather situations (fifty for the European model)--do have a number of their 20 - 50 runs that develop 94L into a tropical depression, but none of these solutions have the storm that develops making it as far west as the Lesser Antilles Islands. The operational high-resolution versions of our three top models for predicting genesis of tropical cyclones--the GFS, European, and UKMET models--have one model, the European model, that does show possible development of 94L into a tropical depression by Sunday. In their 8 am Thursday Atlantic Tropical Weather Outlook., NHC gave 94L 2-day and 5-day odds of development of 10% and 30%, respectively.


Figure 1. Latest satellite image of Invest 94L near the Cape Verde Islands.

Hawaii should watch Guillermo
In the Eastern Pacific, Tropical Storm Guillermo has formed, and is something Hawaii should watch. Both the GFS and European models show Guillermo (or its remnants) getting within 500 miles of the islands by Tuesday, though the storm should be weakening at that time due to dry, stable air and cooler ocean temperatures.


Figure 2. Tropical Cyclone Two in the Bay of Bengal as seen at 05 UTC July 30, 2015, from the MODIS instrument on NASA's Terra satellite. JTWC gave top winds of 40 mph to the system, which made landfall over Bangladesh. Image credit: NASA.

Bay of Bengal's Tropical Cyclone Two kills 27
Tropical Cyclone Two made landfall near Chittagong, Bangladesh, on Thursday morning, bringing heavy rains and deadly landslides to portions of Bangladesh and Myanmar. At least 27 people have been killed in Bangladesh and Myanmar from the storm, according to an article by TWC's Nick Wiltgen. The coastal city of Chittagong reported 879 millimeters (34.61 inches) of rain in just a four-day period July 24 through 27 from the storm.

This may be my last post for a week, as I plan on taking some vacation time and turning the blog over to Bob Henson. He will have the latest installment in our "what to expect from El Niño" series--on how El Niño might affect winter weather in the Eastern U.S.--late this morning.

Jeff Masters