BULLETIN Tropical Storm Irma Intermediate Advisory Number 49A NWS National Hurricane Center Miami FL AL112017 800 AM EDT Mon Sep 11 2017
...IRMA WEAKENS TO A TROPICAL STORM BUT STILL PRODUCING SOME WIND GUSTS TO NEAR HURRICANE FORCE...
SUMMARY OF 800 AM EDT...1200 UTC...INFORMATION ---------------------------------------------- LOCATION...29.5N 82.9W ABOUT 30 MI...50 KM NNE OF CEDAR KEY FLORIDA ABOUT 105 MI...170 KM NNW OF TAMPA FLORIDA MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H PRESENT MOVEMENT...NNW OR 340 DEGREES AT 18 MPH...30 KM/H MINIMUM CENTRAL PRESSURE...970 MB...28.64 INCHES
WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY:
The Storm Surge Warning is discontinued from south of the Flagler/Volusia County line to Jupiter Inlet.
The Hurricane Warning from Sebastian Inlet to Fernandina Beach is changed to a Tropical Storm Warning.
The Hurricane Warning from Anclote River to Indian Pass is changed to a Tropical Storm Warning.
The Hurricane Watch from north of Fernandina Beach to Edisto Beach is discontinued.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Storm Surge Warning is in effect for... * South Santee River southward to the Flagler/Volusia County line * Cape Sable northward to the Ochlockonee River * Tampa Bay
A Tropical Storm Warning is in effect for... * Bonita Beach to the Okaloosa/Walton County Line * Jupiter Inlet to the South Santee River * Lake Okeechobee
A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.
Interests elsewhere in the southeastern United States should monitor the progress of Irma.
For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.
DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 800 AM EDT (1200 UTC), the center of Tropical Storm Irma was located near latitude 29.5 North, longitude 82.9 West. Irma is moving toward the north-northwest near 18 mph (30 km/h) and this motion is expected to continue through Tuesday. On the forecast track, the center of Irma will move near the northwestern coast of the Florida Peninsula this morning, cross the eastern Florida Panhandle into southern Georgia this afternoon, and move through southwestern Georgia and eastern Alabama tonight and Tuesday.
Maximum sustained winds have decreased to near 70 mph (110 km/h) with higher gusts. Additional slow weakening is forecast, and Irma is expected to weaken to a tropical depression by Tuesday afternoon.
Irma has a very large wind field. Hurricane-force winds extend outward up to 60 miles (95 km) mainly to the west of the center, and tropical-storm-force winds extend outward up to 415 miles (665 km).
The estimated minimum central pressure is 970 mb (28.64 inches).
HAZARDS AFFECTING LAND ---------------------- STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water is expected to reach the following HEIGHTS ABOVE GROUND if the peak surge occurs at the time of high tide...
Cape Sable to Captiva...2 to 4 ft Captiva to Anna Maria Island...3 to 5 ft North Miami Beach to Cape Sable, including the Florida Keys...1 to 2 ft Anna Maria Island to Clearwater, including Tampa Bay...2 to 4 ft South Santee River to Fernandina Beach...4 to 6 ft Clearwater Beach to Ochlockonee River...4 t 6 ft Fernandina Beach to Jupiter Inlet...3 to 5 ft
The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.
WIND: Tropical storm conditions will continue across portions of the central and northern Florida peninsula, and are spreading into southern Georgia. Tropical storm conditions should spread into the eastern Florida Panhandle today. Tropical storm conditions are also expected to spread northward across the remainder of the warning areas through today.
Rainfall: Irma is expected to produce the following rain accumulations through Wednesday:
The Florida Keys and southern Florida peninsula: additional 1 inch.
Central Florida peninsula: additional 1 to 3 inches.
Northern Florida peninsula and southern Georgia: additional 3 to 6 inches with storm total amounts of 8 to 15 inches.
Central Georgia, eastern Alabama and southern South Carolina: 3 to inches, isolated 10 inches.
Central Florida Panhandle, western Alabama, northern Mississippi, southern Tennessee, northern Georgia, northern South Carolina and western North Carolina: 2 to 4 inches.
TORNADOES: A few tornadoes are possible across northeast Florida and southeast portions of Georgia and South Carolina through tonight.
SURF: Swells generated by Irma are affecting the southeast coast of the United States. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office.
Irma is continuing to weaken as it moves across the western Florida peninsula, with the eye dissipating and weakening banding near the center. There are no recent observations of hurricane-force winds near the center, but based on the premise that such winds still exist over the Gulf of Mexico west of the center the initial intensity is reduced to 65 kt. It should be noted that near- hurricane force winds are occurring in a band well northeast of the center with sustained winds of 60 kt reported in the Jacksonville area. The cyclone should continue to weaken as it moves through the southeastern United States, becoming a tropical storm later today, a tropical depression by 36 h, and a remnant low by 48 h. The large-scale models forecast Irma to dissipate completely by 72 h, so the 72 h point has been removed from the forecast.
The initial motion is 340/16. The cyclone is expected to move around the eastern side of a mid-level disturbance currently located along the U.S. Gulf Coast, which should cause a north-northwestward to northwestward motion until dissipation. The forecast track takes the center across the eastern Florida Panhandle, southwestern Georgia, eastern and northern Alabama, and eventually into western Tennessee.
KEY MESSAGES:
1. There is the danger of life-threatening storm surge flooding along portions of the coasts of Florida, Georgia and South Carolina, where a Storm Surge Warning remains in effect.
2. Irma will continue to bring life-threatening wind impacts to much of central and north Florida, with hurricane-force winds near the center. Also, Irma is a large hurricane, and hurricane-force wind gusts and sustained tropical-storm force winds extend far from the center. Wind hazards from Irma will continue to spread northward through Georgia and into portions of Alabama, Tennessee, South Carolina, and North Carolina.
3. Irma continues to produce very heavy rain and inland flooding across much of the northern peninsula and eastern panhandle of Florida and southern Georgia, which is quickly spreading to the rest of the southeast United States. Intense rainfall rates of 2 inches or more per hour is leading to flash flooding and rapid rises on creeks, streams, and rivers. Significant river flooding is likely over the next five days in the Florida peninsula and southern Georgia, where average rainfall totals of 8 to 15 inches are expected. Significant river flooding is possible beginning Monday and Tuesday in much of central Georgia and southern South Carolina where average rainfall of 3 to 6 inches and isolated 10 inch amounts are expected. Portions of these states within the southern Appalachians will be especially vulnerable to flash flooding. Farther north and west, Irma is expected to produce average amounts of 2 to 4 inches in parts of Mississippi, Alabama, and Tennessee, northern South Carolina and western North Carolina, where isolated higher amounts and local flooding may occur.