91L a Heavy Rain Threat for Texas/Louisiana; Hurricane Carlos a Threat to Mexico

An area of low pressure over Mexico's Yucatan Peninsula formed Saturday morning, and has the potential to become a tropical depression over the Gulf of Mexico on Monday. The disturbance, designated Invest 91L by NHC on Saturday morning, was bringing a large area of intense thunderstorms to the Western Caribbean on Saturday afternoon, as seen on satellite images. Strong easterly winds of 29 mph, gusting to 43 mph, were observed at the Yucatan Basin buoy on Saturday morning. The heavy thunderstorm activity will push across Mexico's Yucatan Peninsula and into the southern Gulf of Mexico on Sunday, then move north to northwest towards Texas and Louisiana on Monday. The 12Z Saturday run of the SHIPS model predicted that wind shear would be marginal for development, a moderately high 15 - 25 knots, Sunday and Monday. Ocean temperatures in the Gulf of Mexico are warm enough to support a tropical storm, 27.5°C (81.5°F), and the atmosphere is very moist. In their 8 am EDT Saturday Tropical Weather Outlook, NHC gave 2-day and 5-day odds of development of 20% and 30%, respectively. The disturbance will push northwestwards over Texas by Tuesday, but it is uncertain how much rain Texas and Louisiana might get from the storm. The European model favors a more westward track into South Texas with lower rainfall totals of about 1 - 2" over Texas on Monday and Tuesday, while the GFS model shows more development of 91L and a track more towards the east, with the upper Texas coast and Louisiana coast getting about 3 - 5" of rain. Given the amount of heavy thunderstorm activity 91L has already built over the Western Caribbean, I support the wetter forecast of the GFS model for Texas and Louisiana. The Hurricane Hunters are on call to fly into 91L on Monday morning.


Figure 1. Latest satellite image of Invest 91L (right side of image) and Hurricane Carlos (left side of image.)


Figure 2. Radar image of Hurricane Carlos from the Acapulco, Mexico radar, taken at 12:15 pm EDT June 13, 2015. The eyewall had a gap in its west side, and the heaviest rain bands were just offshore.

Hurricane Carlos a heavy rain threat for Mexico
Tropical storm warnings and hurricane watches are up for the Southwest coast of Mexico, as Hurricane Carlos continues its slow intensification process. Carlos became a hurricane about 140 miles south of Acapulco, Mexico, at 11am EDT June 13, marking the second earliest date that we've observed the Northeast Pacific's third hurricane of the year. The record is held by the third hurricane of 1956, which reached hurricane strength on June 12. With very warm waters of 30°C (86°F) beneath it and wind shear a moderate 10 - 20 knots, Carlos is likely to continue a slow intensification process through Monday. On Monday and Tuesday, decreasing ocean temperatures, increasing interaction with land, and drier air will likely cause Carlos to weaken. Satellite loops and radar out of Acapulco shows that the outer spiral bands of Carlos have pushed onshore, but the storm's heaviest rains were just offshore on Saturday. Acapulco recorded sustained winds of 26 mph, gusting to 39 mph, at noon EDT Saturday. The computer models are now more unified in showing Carlos coming closer to the Mexican coast, and Carlos represents a dangerous heavy rain threat to the coast. The 00Z Saturday run of the reliable European model showed Carlos making landfall near Manzanillo, Mexico on Tuesday morning; the 06Z Saturday run of the equally reliable GFS model showed a Tuesday evening landfall near Manzanillo. Heavy rains of 5 - 10 inches will likely affect portions of the Southwest Mexican coast Saturday through Wednesday, which will cause flash flooding and mudslides.

Jeff Masters