![]() I expect Harvey will be a Category 2 hurricane by Friday morning and a Category 3 hurricane by Friday night. Now that Harvey has a well-formed structure, I don’t see any impediments to it intensifying right up until landfall. Image credit: Naval Research Lab, Monterey. The eye was clearly evident as a blue spot with a semicircular partial eyewall (red colors) seen along the southern side of the eye. Microwave satellite image of Harvey at 8:27 am EDT Thursday, August 24, 2017. The outer bands of Harvey are visible on Brownsville long-range radar.įigure 2. Warm waters extended deep into the ocean, providing a large reservoir of heat for the storm to draw upon. The atmosphere had a high mid-level relative humidity of 70%, and the ocean was very warm, with sea surface temperatures (SSTs) of 30.5☌ (87☏.) This was about 2☏ above average for this time of year. Wind shear was light, 5 – 10 knots, which is favorable for intensification. High cirrus clouds streaming away from the center showed the presence of upper-level outflow to the north and east, which was ventilating the storm and allowing intensification to occur. The eye was just beginning to appear on both visible and infrared imagery at 10 am CDT. Harvey had an intense ring of heavy thunderstorms surrounding the eye, and solid low-level spiral bands were forming. Satellite images showed that Harvey was a large storm, whose high-level cirrus clouds were already spreading over extreme southern Texas. It takes up to six hours for a tropical cyclone's winds to respond to a fall in pressure, so I expect that Harvey will be a hurricane by the 4 pm CDT Thursday advisory.Ĭonditions in the Gulf of Mexico on Thursday morning were very favorable for intensification. This is the central pressure that a Category 1 hurricane typically has, but the Hurricane Hunters measured top surface winds of just 65 mph. By 10 am CDT, the pressure had fallen another 2 mb, to 982 mb. By 8:04 am CDT, the eye had completely closed off, and the pressure had fallen another 2 mb, to 984 mb. Earliest reasonable arrival time of tropical storm-force winds for Harvey, from the 10 am CDT Thursday NHC advisory.Īt 6:42 am CDT Thursday, an Air Force hurricane hunter plane found that Harvey had formed a partial eyewall, with a 986 mb pressure. Tropical storm-force winds may arrive along the coast of Texas as early as 8 am CDT Friday, making evacuation difficult thereafter, according to the latest National Hurricane Center (NHC) forecast.įigure 1. If you live on the coast of Texas, please heed the advice of local emergency management officials, and get out today if you live in an evacuation zone. Update: The National Hurricane Center (NHC) has upgraded Harvey to a Category 1 hurricane with 80-mph sustained winds as of noon CDT Thursday. ![]() Harvey was still a tropical depression at 10 pm CDT Wednesday night, but has explosively intensified in the early morning hours, and is almost certain to be a hurricane later today. Hurricane Warnings and Storm Surge Warnings are up for portions of the coast of Texas as rapidly intensifying Tropical Storm Harvey heads north-northwest at 10 mph over the Gulf of Mexico. ![]() GOES-16 images are preliminary and non-operational. Image credit: NASA/MSFC Earth Science Branch. Above: GOES-16 infrared satellite image of Harvey as of 1426Z ( 9:26 am CDT) Thursday, August 24, 2017. ![]()
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