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Tropical Storms Ingrid and Manuel: Extreme Rainfall Threats for Mexico

By: Dr. Jeff Masters, 3:38 PM GMT on September 14, 2013

Extremely dangerous Tropical Storm Ingrid is near hurricane strength as it heads northwards over the Southwestern Gulf of Mexico's Bay of Campeche. Ingrid is embedded in a very moist environment, making it the most dangerous Atlantic Tropical Cyclone of 2013 thus far, due to its rainfall potential. The storm is already bringing sporadic heavy rains to the Eastern Mexican coast near Tampico, but the storm's heaviest rains remain offshore, as seen on Mexican radar. Satellite loops show that Ingrid is steadily growing in size, and the storm's heavy thunderstorms have cold cloud tops that reach high into the atmosphere. The Hurricane Hunters found 70 mph surface winds in Ingrid Saturday morning. Moderate wind shear of 15 - 20 knots is interfering with development, but ocean temperatures are a very warm 29 - 29.5°C (84 - 85°F).


Figure 1. Percent chance of receiving more than 8" of rain during a five day period, from the Saturday 2 am EDT run of the experimental GFDL ensemble model for Tropical Storm Ingrid. More than 8" of rain are predicted for large swaths of Mexico, due, in part, to the effects of Tropical Storm Manuel in the Pacific. Image credit: NOAA/GFDL.

Forecast for Ingrid
All of the models predict that Ingrid's current northerly motion will be short-lived, as a ridge of high pressure builds in to its north and forces the storm nearly due west into Mexico on Monday. The soils along the Mexican Gulf Coast in the state of Veracruz where Ingrid will be dumping some of its heaviest rains are already saturated from the rains of Tropical Depression Eight and Tropical Storm Fernand,. Additional heavy rains affected the region early this week, leading to flash flooding and multiple landslides, including one massive landslide in the town of Manzanatitla on Monday that killed eight people. It won't take much rain to generate a catastrophic flood disaster, and 10 - 15 inches of rain, with isolated amounts of up to 25", are expected.


Figure 2. Twin scourges assault Mexico: Hurricane Ingrid in the Atlantic and Tropical Storm Manuel in the Pacific, at 3:47 pm CDT September 14, 2013.

At the same time that Ingrid is making landfall, Tropical Storm Manuel will be bringing similar rainfall amounts to the other side of Mexico. This morning's 2 am EDT run of the experimental GFDL ensemble model predicted that a large area of Mexico is at high risk of 8+ inches of rain due to the combined effects of Ingrid and Manuel. The greatest danger is on the Pacific side in Oaxaca State, where the combined effects of the circulations of the two storms will pull a flow of very moist air upwards over the mountains, creating torrential rains. The Mexican Weather Service has already received a report of about 8 inches of rain in eastern Mexican state of Oaxaca due to Manuel's rains. The massive rains that will fall in Mexico from this one-two punch of extremely wet tropical storms will cause an extremely dangerous and expensive flood disaster in Mexico.

Jeff Masters

Hurricane

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