Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 2:20 PM GMT on September 18, 2013
Tropical Storm Manuel has regenerated into a strong tropical storm just west of Mexico's Baja Peninsula this Wednesday morning, and the destructive storm promises to bring even more misery to a Mexican nation already reeling from the combined one-two punch of Manuel on its Pacific coast and Hurricane Ingrid on the Atlantic coast earlier this week. The two storms, which hit Mexico within 24 hours of each other on Monday and Tuesday, are now being blamed for the deaths of at least 57 people in Mexico. It was the first time since 1958 that two tropical storms or hurricanes had hit both of Mexico's coasts within 24 hours. Hardest hit was the Acapulco region on Mexico's Pacific coast, where the airport is barely functioning, many roads still flooded and blocked, and tens of thousands of tourists are scrambling to get home. Acapulco received 7.41" of rain from Manuel September 12 - 16, and much higher amounts of rain fell in the surrounding mountains. Newly regenerated Manuel promises to bring 5 - 10" of rain to the Mexican state of Sinaloa, which is likely to cause dangerous flash floods and mudslides.
Figure 1. A soldier wades through the water at the airport of Acapulco, after floods from Tropical Storm Manuel hit on September 17, 2013. Image credit: Pedro Pardo/AFP/Getty Images).
Figure 2. View of a street in Acapulco, Guerrero state, Mexico, after a landslide caused by heavy rains from Tropical Storm Manuel on September 15, 2013. Image credit: CLAUDIO VARGAS/AFP/Getty Images)
Figure 3. Storm sandwich: Tropical Storm Manuel and Hurricane Ingrid lay siege to Mexico on September 15, 2013. Tropical Storm Manuel came ashore on the Pacific coast near Manzanillo on the afternoon of September 15, and Hurricane Ingrid followed suit from the Atlantic on September 16. Image credit: NASA.
Invest 95L headed for Bay of Campeche
Waterlogged Mexico has yet another tropical rain-making system to worry about this week. An area of disturbed weather (Invest 95L) over the Yucatan Peninsula will emerge into the Southwestern Gulf of Mexico's Bay of Campeche by Wednesday night. Satellite loops show that 95L already has a pronounced spin and a respectable area of heavy thunderstorms. Wind shear is moderate, and ocean temperatures are warm, 29°C (84°F.) A hurricane hunter flight is scheduled to investigate 95L on Thursday afternoon.
Invest 95L will likely stay trapped in the Bay of Campeche
Wind shear is expected to be low to moderate over the next five days. There is some dry air over the Bay of Campeche, but I doubt this will be an impediment to development, given the low to moderate wind shear. NHC gave the disturbance 2-day development odds of 70% and 5-day odds of 80% in their 8 am EDT Wednesday Tropical Weather Outlook. Steering currents will be weak in the Bay of Campeche over the next five days, and most of the models predict that 95L will stay trapped there, moving slowly and erratically. However, the UKMET model and approximately 20% of the 20 individual forecasts from the GFS ensemble and European Center ensemble predict that 95L will turn north next week and hit the U.S. Gulf Coast. A cold front and associated upper-level trough of low pressure are expected to push southeastwards over the Gulf of Mexico on Saturday, and it is possible that the upper-level westerly winds associated with this weather system will reach far enough south to pull 95L out of the Bay of Campeche. It typically takes a stronger upper-level trough of low pressure to flush a tropical cyclone out of the Bay of Campeche, though, and 95L will most likely stay put. Regardless, tropical moisture from 95L will likely stream northeastwards along the cold front over much of the U.S. Gulf Coast on Saturday and Sunday, bringing heavy rains of 2 - 4". A non-tropical low pressure system is expected to form along this front over the Southeast U.S. on Sunday, spreading heavy rains up the East Coast early next week.
Typhoon Usagi headed for Taiwan
In the Western Pacific, Typhoon Usagi has intensified to a Category 1 storm with 75 mph winds. Further intensification is likely over the next few days, as Usagi is over very warm waters of 29 - 30°C with high heat content, and is under light wind shear of 5 - 10 knots. The official JTWC forecast brings Usagi to a Category 3 storm before encountering Taiwan, when interaction with land could potentially weaken the storm. Satellite images show Usagi has developed a prominent eye surrounded by intense thunderstorms that reach high into the atmosphere. The typhoon is expected to pass north of the Philippines Islands on Friday, and will threaten southern Taiwan on Saturday.
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