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