Irma moves steadily toward Florida

It's pretty much a worst case scenario for emergency preparedness officials.

A major (Category 4) hurricane is moving toward Florida.

Incredibly strong hurricane winds and a significant storm surge are expected to hit much of south Florida, including Miami and Miami Beach, this weekend.

Damage could be catastrophic.

Hurricane Irma update 

The Friday morning update from the National Hurricane Center shows that Hurricane Irma has maximum sustained winds of 150 mph and is moving to the west-northwest at 16 mph.

Irma is expected to move just north of the coast of Cuba Friday and Friday night, then curve northward toward south Florida on Saturday:

Landfall of the eye of Irma in south-central Florida could take place late Saturday night or very early on Sunday.

Since hurricane force winds extend about 70 miles from Irma's center, parts of south Florida will have hurricane force winds hours before landfall.

Here's the Friday morning Irma update from the NHC:

BULLETIN

Hurricane Irma Intermediate Advisory Number 37A

NWS National Hurricane Center Miami FL AL112017

800 AM EDT Fri Sep 08 2017

...CORE OF HURRICANE IRMA FORECAST TO MOVE BETWEEN THE CENTRAL

BAHAMAS AND THE NORTH COAST OF CUBA TODAY...

 

SUMMARY OF 800 AM EDT...1200 UTC...INFORMATION

----------------------------------------------

LOCATION...21.8N 74.7W

ABOUT 80 MI...125 KM NE OF CABO LUCRECIA CUBA

ABOUT 450 MI...720 KM SE OF MIAMI FLORIDA

MAXIMUM SUSTAINED WINDS...150 MPH...240 KM/H

PRESENT MOVEMENT...WNW OR 285 DEGREES AT 16 MPH...26 KM/H

MINIMUM CENTRAL PRESSURE...927 MB...27.37 INCHES

 

WATCHES AND WARNINGS

--------------------

CHANGES WITH THIS ADVISORY:

The Hurricane and Tropical Storm Warnings for Haiti have been

discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for...

* Jupiter Inlet southward around the Florida peninsula to Bonita

Beach

* Florida Keys

A Storm Surge Watch is in effect for...

* North of Jupiter Inlet to Sebastian Inlet

* North of Bonita Beach to Venice

A Hurricane Warning is in effect for...

* Jupiter Inlet southward around the Florida peninsula to Bonita

Beach

* Florida Keys

* Lake Okeechobee

* Florida Bay

* Southeastern Bahamas and the Turks and Caicos Islands

* Cuban provinces of Camaguey, Ciego de Avila, Sancti Spiritus, and

Villa Clara

* Central Bahamas

* Northwestern Bahamas

A Hurricane Watch is in effect for...

* North of Jupiter Inlet to Sebastian Inlet

* North of Bonita Beach to Anna Maria Island

* Cuban provinces of Guantanamo, Holguin, Las Tunas and Matanzas

A Tropical Storm Warning is in effect for...

* Cuban provinces of Guantanamo, Holguin, and Las Tunas

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.

A Storm Surge Watch means there is a possibility of life-

threatening inundation, from rising water moving inland from the

coastline, in the indicated locations during the next 48 hours.

For a depiction of areas at risk, please see the National Weather

Service Storm Surge Watch/Warning Graphic, available at

hurricanes.gov.

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 Hurricane Watch means that hurricane conditions are possible

within the watch area. A watch is typically issued 48 hours

before the anticipated first occurrence of tropical-storm-force

winds, conditions that make outside preparations difficult or

dangerous.

A Tropical Storm Warning means that tropical storm conditions are

expected somewhere within the warning area.

Interests elsewhere in Cuba, Florida, and 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. For storm information specific to your area outside

the United States, please monitor products issued by your national

meteorological service.

 

DISCUSSION AND 48-HOUR OUTLOOK

------------------------------

At 800 AM EDT (1200 UTC), the eye of Hurricane Irma was located near

latitude 21.8 North, longitude 74.7 West. Irma is moving toward the

west-northwest near 16 mph (26 km/h), and this motion is expected to

continue for the next day or so with a decrease in forward speed. A

turn toward the northwest is expected by late Saturday. On the

forecast track, the eye of Irma should move near the north coast

of Cuba and the central Bahamas today and Saturday, and be near the

Florida Keys and the southern Florida Peninsula Sunday morning.

Maximum sustained winds are near 150 mph (240 km/h) with higher

gusts. Irma is a category 4 hurricane on the Saffir-Simpson

Hurricane Wind Scale. Some fluctuations in intensity are likely

during the next day or two, but Irma is forecast to remain a

powerful category 4 hurricane as it approaches Florida.

Hurricane-force winds extend outward up to 70 miles (110 km) from

the center and tropical-storm-force winds extend outward up to 185

miles (295 km).

The latest minimum central pressure reported by a reconnaissance

plane was 927 mb (27.37 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...

Jupiter Inlet to Bonita Beach, including Florida Keys...5 to 10 ft

Bonita Beach to Venice...3 to 5 ft

Jupiter Inlet to Sebastian Inlet...3 to 6 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.

The combination of a life-threatening storm surge and large breaking

waves will raise water levels ABOVE NORMAL TIDE LEVELS by the

following amounts within the hurricane warning area near and to the

north of the center of Irma. Near the coast, the surge will be

accompanied by large and destructive waves.

Turks and Caicos Islands...15 to 20 ft

Southeastern and central Bahamas...15 to 20 ft

Northwestern Bahamas...5 to 10 ft

Northern coast of Haiti and the Gulf of Gonave...1 to 3 ft

Northern coast of Cuba in the warning area...5 to 10 ft

WIND: Hurricane conditions are occurring on the Turks and Caicos

Islands, with tropical storm and hurricane conditions ongoing in the

southeastern Bahamas. These conditions will move into the central

Bahamas later today. Hurricane conditions are expected within the

hurricane warning area along the north coast of Cuba late today and

Saturday. Hurricane conditions are expected in the northwestern

Bahamas tonight and Saturday, and in portions of southern Florida

and the Florida Keys Saturday night or early Sunday.

Hurricane conditions are possible within the watch area in Florida

by Sunday, with tropical storm conditions possible by late Saturday.

RAINFALL: Irma is expected to produce the following rain

accumulations through Tuesday night:

Northern Dominican Republic and northern Haiti...additional 2 to 4

inches.

Southern Dominican Republic and southern Haiti...additional 1 to 2

inches.

Turks and Caicos...additional 3 to 6 inches.

Southern Bahamas and northern Cuba...10 to 15 inches, isolated 20

inches.

Southern Cuba...4 to 8 inches, isolated 12 inches.

The upper Florida Keys into southeast Florida...10 to 15 inches,

isolated 20 inches.

Eastern Florida northward into coastal Georgia...8 to 12 inches,

isolated 16 inches.

Lower Florida Keys...3 to 5 inches.

Western Florida Peninsula into much of Georgia...South

Carolina...and Western North Carolina...3 to 6 inches.

In all areas this rainfall may cause life-threatening flash floods

and in some areas mudslides.

SURF: Swells generated by Irma are affecting Puerto Rico, the

Virgin Islands, the southeastern Bahamas, the Turks and Caicos

Islands, the northern coast of the Dominican Republic, and should

start affecting portions of the southeast coast of the United States

later today and tonight. These swells are likely to cause

life-threatening surf and rip current conditions. Please consult

products from your local weather office.

I hope Floridians aren't lowering their guard just because Irma's max winds are down to 150 mph.

Irma is a major hurricane and only 7 mph below Category 5 status.

Irma could strengthen a bit when she moves over the warm waters south of Florida tomorrow.

Hurricane force winds will reach much of Florida at some point:

Miami details

Here's a summary of Irma's threat to south Florida, from the Miami NWS office:

Storm surge

According to the National Hurricane Center:

Along the coast, storm surge is often the greatest threat to life and property from a hurricane.

NHC defines storm surge as:

Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with normal high tide, resulting in storm tides reaching up to 20 feet or more in some cases.

An illustration of storm surge

In their morning Irma update, the NHC indicated that storm surges from Irma could be 5 to 10 feet above ground level in parts of south Florida this weekend.

In addition to a hurricane warning, there is an extensive part of south Florida under a storm surge warning this weekend:

We'll keep you updated on Hurricane Irma through the weekend.

Nice weekend for Minnesota 

Saturday will be the coolest day this weekend, with highs in the lower 70s south and mostly 60s in central and northern Minnesota.

On Sunday, most of Minnesota should see 70s:

Looking ahead, highs should be around 80 Monday through Wednesday in the Twin Cities metro area.

Programming note

You can hear my live weather updates on Minnesota Public Radio at 7:49 a.m. Thursdays and Fridays, and at 7:35 a.m., 9:35 a.m. and 4:35 p.m. each Saturday and Sunday.