Two tropical waves spinning off the coast of Africa are worth watching for development, but neither poses a foreseeable threat to any land areas. A tropical wave (90L)
located about 700 hundred miles west of the Cape Verde Islands at 10 am EDT on Sunday is headed west to west-northwest at about 10 - 15 mph. Satellite images
show 90L has plenty of spin, but heavy thunderstorm activity is limited. The disturbance is embedded in a very dry air mass, has marginal Sea Surface Temperatures (SSTs) of 26.5°C (80°F) beneath it, and is experiencing moderate wind shear. None of our three reliable computer models for predicting tropical storm formation predicts development of 90L over the next five days. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 10%. The wave should pass a few hundred miles northeast of the northern Lesser Antilles Islands on Thursday.Figure 1.
MODIS satellite image of tropical waves 90L and 91L off the coast of Africa at approximately 8 am EDT Sunday September 7, 2014. Image credit: NASA/GSFC.New African Tropical Wave 91L
A tropical wave (91L)
that emerged from the coast of Africa on Sunday is headed west to west-northwest at about 15 mph. Satellite images
show 91L has a moderate amount of spin and heavy thunderstorm activity. The disturbance is embedded in a moist air mass, has moderately warm (SSTs) of 27.5°C (82°F) beneath it, and is experiencing moderate wind shear. Two of our three reliable computer models for predicting tropical storm formation predict development of 91L over the next five days. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odd of development odds of 30% and 60%, respectively. The wave should take a more northwesterly track by mid-week, and does not appear to be a long-range threat to the Lesser Antilles Islands.Norbert rapidly weakening
In the Eastern Pacific, Hurricane Norbert
weakened to a tropical storm Sunday morning as it moved over cool waters of 25°C (77°F.) Satellite loops
on Sunday morning showed that Norbert had lost almost all of its heavy thunderstorms. The current weakening trend should accelerate until Norbert dissipates by Monday. The counter-clockwise flow of air around the hurricane is pulling moisture from the remnants of Tropical Storm Dolly and from the tropical Eastern Pacific northwards into Northern Mexico and the Southern Arizona, and this moisture will be capable of causing flooding rains in those regions.