MIAMI -- Hurricane Helene...

The 11 a.m. EDT update from the National Hurricane Center says Helene now has top winds of 105 mph. It's centered about 255 miles SW of Tampa and 290 miles S of Apalachicola, moving NNE at 14 mph.

..HELENE STRENGTHENING AND EXPECTED TO MAKE LANDFALL IN THE

FLORIDA BIG BEND THIS EVENING AS A MAJOR HURRICANE...

...PREPARATIONS TO PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO

COMPLETION...

SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION

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LOCATION...25.5N 85.5W

ABOUT 255 MI...405 KM SW OF TAMPA FLORIDA

ABOUT 290 MI...470 KM S OF APALACHICOLA FLORIDA

MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H

PRESENT MOVEMENT...NNE OR 25 DEGREES AT 14 MPH...22 KM/H

MINIMUM CENTRAL PRESSURE...960 MB...28.35 INCHES

WATCHES AND WARNINGS

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CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for...

* Mexico Beach eastward and southward to Flamingo

* Tampa Bay

* Charlotte Harbor

A Hurricane Warning is in effect for...

* Anclote River to Mexico Beach

A Hurricane Watch is in effect for...

* Englewood to Anclote River, including Tampa Bay

A Tropical Storm Warning is in effect for...

* Florida Keys, including the Dry Tortugas

* Flamingo to Anclote River, including Tampa Bay

* West of Mexico Beach to the Okaloosa/Walton County Line

* Flamingo northward to Little River Inlet

* Lake Okeechobee

* Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth

A Storm Surge Warning means there is a danger of life-threatening

inundation, from rising water moving inland from the coastline. 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.

A Hurricane Warning means that hurricane conditions are expected

somewhere within the warning area. Preparations to protect life

and property should be rushed to completion.

A Tropical Storm Warning means that tropical storm conditions are

expected somewhere within the warning area.

A Hurricane Watch means that hurricane conditions are possible

within the watch area.

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. For storm information specific to your area

outside of the United States, please monitor products issued by

your national meteorological service.

DISCUSSION AND OUTLOOK

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At 1000 AM CDT (1500 UTC), the center of Hurricane Helene was

located near latitude 25.5 North, longitude 85.5 West. Helene is

moving toward the north-northeast near 14 mph (22 km/h). A

significant increase in forward speed is expected during the next 24

hours. On the forecast track, Helene will make landfall in the

Florida Big Bend region this evening. After landfall, Helene is

expected to turn northwestward and slow down over the Tennessee

Valley on Friday and Saturday.

Maximum sustained winds have increased to near 105 mph (165 km/h)

with higher gusts. Additional strengthening is forecast, and Helene

is expected to be a major hurricane when it reaches the Florida Big

Bend coast this evening. Weakening is expected after landfall, but

Helene's fast forward speed will allow strong, damaging winds,

especially in gusts, to penetrate well inland across the

southeastern United States, including over the higher terrain of the

southern Appalachians.

Helene is a very large hurricane. Hurricane-force winds extend

outward up to 60 miles (95 km) from the center and

tropical-storm-force winds extend outward up to 345 miles

(555 km).

The minimum central pressure based on data from the Air Force

Hurricane Hunters is 960 mb (28.35 inches).

HAZARDS AFFECTING LAND

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Key Messages for Helene can be found in the Tropical Cyclone

Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC

and on the web at hurricanes.gov/text/MIATCDAT4.shtml

STORM SURGE: The combination of a life-threatening 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 could

reach the following heights above ground somewhere in the indicated

areas if the peak surge occurs at the time of high tide...

Carrabelle, FL to Suwannee River, FL...15-20 ft

Apalachicola, FL to Carrabelle, FL...10-15 ft

Suwannee River, FL to Chassahowitzka, FL...10-15 ft

Chassahowitzka, FL to Anclote River, FL...8-12 ft

Indian Pass, FL to Apalachicola, FL...6-10 ft

Anclote River, FL to Middle of Longboat Key, FL...5-8 ft

Tampa Bay...5-8 ft

Middle of Longboat Key, FL to Englewood, FL...4-7 ft

East of Mexico Beach, FL to Indian Pass, FL...3-5 ft

Englewood, FL to Flamingo, FL...3-5 ft

Charlotte Harbor...3-5 ft

The deepest water will occur along the immediate coast near and to

the east of the landfall location, where the surge will be

accompanied by large and dangerous 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.

For a complete depiction of areas at risk of storm surge inundation,

please see the National Weather Service Peak Storm Surge Graphic,

available at hurricanes.gov/graphics_at4.shtml?peakSurge.

WIND: Hurricane conditions are expected within the U.S. hurricane

warning area late today. Tropical storm conditions have

already begun in the Florida Keys and portions of south

Florida, and these conditions are expected to spread northward

across the tropical storm warning areas in the southeastern U.S.

through early Friday. Strong, damaging winds, especially in gusts,

will likely penetrate as far inland as the higher terrain of the

southern Appalachians.

Tropical storm conditions are expected over portions of the warning

area in western Cuba during the next couple of hours.

RAINFALL: Hurricane Helene is expected to produce total rain

accumulations of 4 to 8 inches over western Cuba. This rainfall

brings a risk of considerable flooding.

Over portions of the Southeastern U.S. into the Southern

Appalachians, Helene is expected to produce total rain accumulations

of 6 to 12 inches, with isolated totals around 20 inches. This

rainfall will likely result in catastrophic and potentially

life-threatening flash and urban flooding, along with significant

river flooding. Numerous significant landslides are expected in

steep terrain across the southern Appalachians.

For a complete depiction of forecast rainfall associated with

Hurricane Helene, please see the National Weather Service Storm

Total Rainfall Graphic, available at

hurricanes.gov/graphics_at4.shtml?rainqpf and the Flash Flood Risk

graphic at hurricanes.gov/graphics_at4.shtml?ero.

For a list of rainfall observations (and wind reports) associated

this storm, see the companion storm summary at WBCSCCNS4 with the

WMO header ACUS44 KWBC or at the following link:

www.wpc.ncep.noaa.gov/discussions/nfdscc4.html.

TORNADOES: The risk for several tornadoes will gradually increase

today through tonight. The greatest threat is expected from parts of

northern Florida into southeast Georgia, the Midlands and Low

Country of South Carolina, and southern North Carolina.

SURF: Swells generated by Helene will affect much of Florida and

the coasts of Georgia and the Carolinas during the next couple of

days. Swells will also continue across portions of Cuba and the

Yucatan Peninsula through tonight. These swells are likely to cause

life-threatening surf and rip current conditions. Please consult

products from your local weather office.

Photo: NHC

Operativo Storm Watch