Written by Amy Godsey, Florida State Meteorologist Tuesday, 28 August 2012 07:40
5am, Tuesday, 8/28/12, Summary:
At 5am EDT Tuesday, Tropical Storm Isaac was located about 205 miles south-southwest of Pensacola, Florida, and 205 miles southeast of New Orleans, Louisiana.
Isaac is moving northwest around 12 mph. This general motion, with a gradual decrease in forward speed, is expected today, followed by a turn to the north on Thursday.
Computer models are in better agreement (with a range of possibilities between Mississippi and the Louisiana/Texas border), and Isaac should make landfall by Wednesday morning in Southeast Louisiana.
The official NHC forecast has the center of Isaac making landfall between Plaquemines and Terrebonne Parishes around midnight tonight, reaching near Baton Rouge Wednesday afternoon, then moving north into Arkansas Thursday afternoon.
Maximum sustained winds remain near 70 mph. Isaac is still forecast to become a hurricane later today.
Isaac has a rather large circulation and no well-defined core. In addition, an upper level low pressure area near Isaac for the past few days has resulted in some increased shear. Although Isaac is moving through very warm waters, the lack of definition and shear will prohibit any rapid strengthening.
Isaac remains a large storm, and tropical storm force winds extend as far as 205 miles from the center. Due to the large wind field associated with Isaac, effects will continue to be felt far away from the center.
An area of low pressure in the central Atlantic, designated as invest area 97L, has changed little in organization. Environmental conditions are forecast to become increasingly hostile for development in a few days as it moves northwest at 10-15mph.
The National Hurricane Center is forecasting a medium (30%) chance of becoming a tropical depression within the next 2 days.
A tropical wave near the Cape Verde Islands may begin to organize over the next several days. There is currently only a 10% chance of becoming a tropical cyclone within the next 48 hours, but chances may increase later this week as it moves west around 15mph.
Watches and Warnings Issued for Florida:
Tropical Storm Warning – Aucilla River to FL/AL border. This includes the counties of Escambia, Santa Rosa, Okaloosa, Walton, Gulf, Bay, coastal Franklin, coastal Wakulla, coastal Jefferson.
The large nature of Isaac could still produce tropical storm force winds in portions of the Florida Panhandle. All of Florida has a less than 5% chance of seeing hurricane force winds.
Although sustained tropical storm force winds are not expected in the Florida Big Bend (except in strong rainbands), gusts to tropical storm force are possible. Also, large storm tide heights are still expected in Apalachee Bay and a Tropical Storm Watch includes the hazard for wind and surge.
Storm tide (surge + tide) heights may reach 3-6 feet along the Florida Panhandle west of Panama City/West Bay and in Apalachee Bay. 1-3 feet of surge is possible from Panama City/East Bay to Port St. Joe, and along the Florida Nature Coast from Levy to southern Taylor County.
Large waves and lingering ocean swells will result in a moderate to high risk of rip currents statewide. A Coastal Flood Advisory is in effect from Taylor County to Lee County, with a Rip Current Advisory for Northeast Florida.
Although most of the strongest storm activity is offshore, heavy rainfall could affect much of Northwest Florida today as the outer bands of Isaac rotate northward.
2-5 inches of rain will be possible over much of North Florida for the next few days. Higher rainfall totals of 6-9 inches with higher amounts to 12-15 inches are possible in the western Panhandle. A Flash Flood Watch is in effect for Escambia County through 2am Wednesday. Gusty winds will be capable of knocking down trees in saturated ground.
2-4 inches of rainfall has fallen over much of Central South Florida since Sunday morning. Higher amounts of 6-10 inches have fallen over some areas of Miami-Dade, Broward, Palm Beach, Martin, St. Lucie, Indian River and Okeechobee Counties, with as much as 9-13 inches in parts of Palm Beach, Martin and St. Lucie Counties.
Additional rainfall up to 2 inches is possible over Central and South Florida for the next 2 days as a typically summertime pattern brings the potential for heavy afternoon showers and thunderstorms.
The Storm prediction Center has placed Northwest Florida in a slight risk for severe weather on Tuesday and Wednesday.
More information on Tropical Storm Isaac and 97L can be found at www.nhc.noaa.gov.
Click here to view storm related images and graphics. Another update will be issued Tuesday afternoon.
State Watch Officer
Florida Division of Emergency Management
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