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 , 2:02 PM GMT on August 06, 2012
Tropical Storm Ernesto is undergoing significant strengthening, and is not far from hurricane strength, according to data from this morning's Hurricane Hunter mission. The Air Force hurricane hunter aircraft in the storm found the pressure had dropped to 997 mb at 8:13 am EDT, and had dropped another 3 mb to 994 mb at 9:17 am. Surface winds as seen by their SFMR instrument had increased to 68 mph, and the plane found 89 mph winds at their flight level of 5,000 feet, on the northwest side of the eye. A full eyewall surrounding a small 9-mile diameter eye had formed. Ernesto's forward speed has slowed down to 12 mph--just half of what it was 24 hours ago, and this has allowed the surface center to align itself with the circulation at middle levels of the atmosphere. Visible satellite loops show that Ernesto's heaviest thunderstorms are now located near the center of the storm, and these thunderstorms have expanded in areal extent and intensity to form a Central Dense Overcast (CDO), a feature of intensifying tropical storms. Ernesto is still battling moderate wind shear of 10 - 15 knots, due to strong upper-level winds out of the west. Water vapor satellite loops show dry air to the west, but the environment around Ernesto is the moistest we've seen since it entered the Caribbean. On Sunday, Ernesto brought 1.73" of rain to Kingston, Jamaica, and top sustained winds of 37 mph.
Figure 1. Morning satellite image of Ernesto.
Forecast for Ernesto
Now that Ernesto has slowed down in response to a trough of low pressure passing to the north, continued steady intensification appears likely. While wind shear is expected to remain in the moderate range the next two days, Ernesto is over warm ocean waters of 28°C with very high heat content, and rapid intensification to a Category 2 hurricane is possible today. The 8 am EDT SHIPS model forecast predicts a 26% chance of rapid intensification--a 30 mph increase in winds over a 24-hour period. The main obstacle to intensification will probably be proximity to land, as the center of Ernesto is likely to pass very close to the coast of Honduras late Monday night. This will put a portion of the storm's circulation over land, limiting intensification potential.
The winds this Monday morning at Puerto Lempira on the northeast coast of Honduras have not yet begun to increase, but will begin to rise this afternoon and peak near midnight tonight. High winds and heavy rains will spread westwards along the coast of Honduras early Tuesday morning, and reach coastal Belize near 2 pm Tuesday. If Ernesto survives its crossing of the Yucatan Peninsula, the potential exists for it to re-strengthen over the Bay of Campeche, and make a second landfall on Mexico's coast Thursday night south of Veracruz. However, most of the computer models predict that Ernesto will pop out so far south in the Bay of Campeche that the storm will have less than 24 hours over water. This makes significant re-intensification unlikely. I don't expect rain from Ernesto will get as far north as Brownsville, Texas.
Tropical Storm Florence
Tropical Depression Florence is dissipating due to dry air and cool waters, and is not a threat to re-develop.
Historic heat wave ends in Oklahoma
The high temperature in Oklahoma City on Sunday reached 99°, snapping a string of 18 straight days the temperature had reached 100° or greater. The latest forecast calls for a few more days of temperatures in excess of 100° this week, but nothing like the heat wave last week that brought an unprecedented three straight days of 112° heat. The winds today in Oklahoma will be considerably lower than we saw over the weekend, which will aid firefighting efforts.
Wunderground's weather historian Christopher C. Burt has a new post on July's heat extremes in the U.S.
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