Updraft® - Minnesota Weather News

Hurricane Harvey update; weekend rain chances

Hurricane Harvey is on the verge of becoming a major (Category 3) hurricane this Friday morning.

The National Oceanic and Atmospheric Administration’s mix of infrared and visible satellite pictures shows Harvey's slow movement toward the Texas coast since midnight:

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NOAA satellire early Friday

Maximum sustained winds are at 110 mph, so any strengthening will push Harvey into Category 3 (major) hurricane status.

The Saffir-Simpson scale is used by the National Hurricane Center to rate hurricane strength:

The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based on a hurricane's sustained wind speed. This scale estimates potential property damage. Hurricanes reaching Category 3 and higher are considered major hurricanes because of their potential for significant loss of life and damage. Category 1 and 2 storms are still dangerous, however, and require preventative measures. In the western North Pacific, the term "super typhoon" is used for tropical cyclones with sustained winds exceeding 150 mph.

Here are the criteria for the various hurricane categories used by the NHC:

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National Hurricane Center

Now, the latest Hurricane Harvey update from the National Hurricane Center:

BULLETIN

Hurricane Harvey Intermediate Advisory Number 20A

NWS National Hurricane Center Miami FL AL092017

700 AM CDT Fri Aug 25 2017

...PREPARATIONS ALONG THE MIDDLE TEXAS COAST SHOULD BE RUSHED TO

COMPLETION THIS MORNING...

...CONDITIONS EXPECTED TO DETERIORATE THROUGH THE DAY...

 

SUMMARY OF 700 AM CDT...1200 UTC...INFORMATION

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

LOCATION...26.3N 95.8W

ABOUT 140 MI...225 KM SE OF CORPUS CHRISTI TEXAS

ABOUT 145 MI...235 KM SSE OF PORT OCONNOR TEXAS

MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H

PRESENT MOVEMENT...NW OR 315 DEGREES AT 10 MPH...17 KM/H

MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES

 

WATCHES AND WARNINGS

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

CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for...

* Port Mansfield to High Island Texas

A Storm Surge Watch is in effect for...

* South of Port Mansfield Texas to the Mouth of the Rio Grande

A Hurricane Warning is in effect for...

* Port Mansfield to Sargent Texas

A Tropical Storm Warning is in effect for...

* North of Sargent to High Island Texas

* South of Port Mansfield Texas to the Mouth of the Rio Grande

A Hurricane Watch is in effect for...

* South of Port Mansfield Texas to the Mouth of the Rio Grande

A Tropical Storm Watch is in effect for...

* South of the Mouth of the Rio Grande to Boca de Catan Mexico

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

inundation from rising water moving inland from the coastline 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 Hurricane Warning means that hurricane conditions are expected

somewhere within the warning area, in this case within the next 12

to 24 hours. Preparations to protect life and property should be

rushed to completion.

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.

A Hurricane Watch means that hurricane conditions are possible

within the watch area.

In addition, interests in southwestern Louisiana should continue to

monitor the progress of this system.

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 700 AM CDT (1200 UTC), the eye of Hurricane Harvey was located

by Air Force Reserve reconnaissance aircraft and NOAA Doppler radar

near latitude 26.3 North, longitude 95.8 West. Harvey is moving

toward the northwest near 10 mph (17 km/h), but its forward speed

is expected to decrease significantly during the next couple of

days. On the forecast track, Harvey will make landfall on the

middle Texas coast tonight or early Saturday. Harvey is then likely

to meander near or just inland of the middle Texas coast through the

weekend.

Maximum sustained winds are near 110 mph (175 km/h) with higher

gusts. Some strengthening is possible, and Harvey is expected to

become a major hurricane before it reaches the middle Texas coast.

Hurricane-force winds extend outward up to 35 miles (55 km) from

the center, and tropical-storm-force winds extend outward up to 140

miles (220 km).

The minimum central pressure reported by the Air Force plane was 950

mb (28.05 inches).

 

HAZARDS AFFECTING LAND

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

RAINFALL: Harvey is expected to produce total rain accumulations

of 15 to 25 inches and isolated maximum amounts of 35 inches over

the middle and upper Texas coast through next Wednesday. During

the same time period Harvey is expected to produce total rain

accumulations of 7 to 15 inches in far south Texas and the Texas

Hill Country eastward through central and southwest Louisiana, with

accumulations of up to 7 inches extending into other parts of Texas

and the lower Mississippi Valley. Rainfall from Harvey will cause

devastating and life-threatening flooding.

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...

N Entrance Padre Island Natl Seashore to Sargent...6 to 12 ft

Sargent to Jamaica Beach...5 to 8 ft

Port Mansfield to N Entrance Padre Island Natl Seashore...5 to 7 ft

Jamaica Beach to High Island...2 to 4 ft

Mouth of the Rio Grande to Port Mansfield...2 to 4 ft

High Island to Morgan City...1 to 3 ft

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

the northeast of the landfall location, 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: Hurricane conditions are likely within the hurricane warning

area later today and tonight, with tropical storm conditions

expected to first reach the coast in the hurricane warning area

later this morning. These conditions are likely to persist

into Saturday in portions of the hurricane and tropical storm

warning area.

SURF: Swells generated by Harvey will begin to affect the Texas,

Louisiana, and northeast Mexico coasts later this morning. These

swells are likely to cause life-threatening surf and rip current

conditions. Please consult products from your local weather

office.

TORNADOES: Isolated tornadoes are possible across portions of the

middle and upper Texas coast today.

Of special note in the latest NHC advisory is this sentence:

Harvey will make landfall on the middle Texas coast tonight or early Saturday. Harvey is then likely

to meander near or just inland of the middle Texas coast through the weekend.

That is a change from most hurricanes, which typically move well inland and weaken.

As a result of Harvey's expected path, rainfall amounts of over 20 inches are possible over the next several days in a large part of south Texas, including Houston:

rt082rain2
NWS/WPC/National Hurricane Center

Here's the latest version of Harvey's possible path:

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National Hurricane Center

The area along the Texas coast that is shaded red is in a hurricane warning.

The National Hurricane Center will issue frequent updates on Hurricane Harvey.

Rain and thunderstorm chances for Minnesota

Minnesota will see some scattered showers and possibly an isolated thunderstorm this Friday and Friday evening.

Periods of rain with a few embedded thunderstorms are expected overnight Friday night and on Saturday.

Our chance of rain on Sunday is lower, but a shower or isolated thunderstorm is still possible.

The National Oceanic and Atmospheric Administration's North American Mesoscale forecast model shows the potential rain pattern Friday through Saturday evening:

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NOAA NAM simulated radar from Friday morning through Saturday evening, via tropicaltidbits

Severe weather outlook

The Storm Prediction Center of the National Weather Service shows a slight risk of severe weather Friday and Friday night for a portion of southwestern Minnesota:

rt0825svr
NWS Storm Prediction Center

Slight risk means that scattered severe weather is possible.

Isolated severe weather is possible in the marginal risk area that covers parts of west-central into south-central Minnesota.

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.