Manuel Hits Mexico Again, 138 Dead or Missing; Cat 4 Usagi a Threat to Hong Kong

Hurricane Manuel made landfall in the Mexican state of Sinaloa almost due east of the tip of the Baja Peninsula this Thursday morning near 8 am EDT, as a Category 1 storm with 75 mph winds. It was Manuel's second landfall this week in storm-weary Mexico. Manuel hit the coast on Monday as a tropical storm with 70 mph winds northwest of Acapulco, bringing torrential rains of up to foot in the coastal mountains. The combined one-two punch of Manuel on Mexico's Pacific coast and Hurricane Ingrid on the Atlantic coast this week have caused flooding blamed for at least 80 deaths. Another 58 people are missing and probably dead in a landslide that hit La Pintada, several hours north of Acapulco. The double blow by Manuel and Ingrid this week was the first time since 1958 that two tropical storms or hurricanes had hit both of Mexico's coasts within 24 hours. Acapulco received 7.41" of rain from Manuel September 12 - 16, and up to a foot of rain fell in the surrounding mountains. Manuel promises to bring 5 - 10" of rain to the Mexican state of Sinaloa, which is likely to cause additional flash floods and mudslides over the next few days. Mexican radar shows that Manuel is moving very slowly inland, and should weaken significantly as long as the eye stays ashore. Satellite images show that Manuel is a small storm, and its heavy rains are affecting a relatively limited area. With such a large death toll, it is possible that the name Manuel will be retired from the list of active Eastern Pacific hurricanes; only three other Pacific storms that hit Mexico have had their names retired.


Figure 1. Hurricane Manuel at landfall in the Mexican state of Sinaloa at 7:15 am EDT September 19, 2013. Image credit: Conagua.


Figure 2. Rainfall for the 9-day period September 9 - 18, 2013, as measured by NASA's TRMM satellite. Rainfall amounts of 12" inches (red colors) affected portions of Mexico near Acapulco. Image credit: NASA.


Figure 3. 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).

Invest 95L in Bay of Campeche
Waterlogged Mexico has yet another tropical rain-making system to worry about--Invest 95L, over the Southwestern Gulf of Mexico's Bay of Campeche. Satellite loops show that 95L has a pronounced spin, but only a small area of heavy thunderstorms. The thunderstorms are causing some isolated heavy downpours along the coast of Mexico, as seen on Mexican radar. Wind shear is moderate, and ocean temperatures are warm, 29°C (84°F.) There is some dry air over the Bay of Campeche, which appears to be slowing down development. A hurricane hunter flight is scheduled to investigate 95L on Thursday afternoon, but I expect this flight will be cancelled, due to 95L's lack of heavy thunderstorms.

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. NHC gave the disturbance 2-day development odds of 70% and 5-day odds of 80% in their 8 am EDT Thursday 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".


Figure 3. MODIS satellite image of Typhoon Usagi, taken at approximately 02:30 UTC on September 19, 2013. At the time, Usagi was a Category 2 storm with 105 mph winds. Image credit: NASA.

Dangerous Typhoon Usagi headed for Taiwan and Hong Kong
In the Western Pacific, powerful and dangerous Typhoon Usagi has intensified to a Category 4 storm with 140 mph winds. Further intensification is likely over the next day, 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 5 super typhoon by Friday, which would make Usagi Earth's first Category 5 storm of 2013. Usagi will pass very close to the southern tip of Taiwan at 06 UTC Saturday (2 am EDT), and interaction with land could potentially weaken the storm. However, Usagi is still expected to be a major Category 3 typhoon when it makes landfall near Hong Kong at approximately 00 UTC Sunday (8 pm EDT Saturday.) Satellite images show that Usagi is a large and very impressive typhoon with a prominent eye surrounded by a thick eyewall with intense thunderstorms that reach high into the atmosphere.

Friday's blog update will be later than usual, as I am taking the day off, and one of wunderground's San Francisco-based meteorologists will be filling in for me.

Jeff Masters