[Tropical] Public Tropical Cyclone Advisory

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WTNT33 KNHC 261742
TCPAT3

BULLETIN
Hurricane Laura Intermediate Advisory Number 27A
NWS National Hurricane Center Miami FL       AL132020
100 PM CDT Wed Aug 26 2020

...AIR FORCE HURRICANE HUNTER AIRCRAFT REPORTS LAURA HAS BECOME AN
EXTREMELY DANGEROUS CATEGORY 4 HURRICANE...
...CATASTROPHIC STORM SURGE, EXTREME WINDS, AND FLASH FLOODING
EXPECTED ALONG THE NORTHWEST GULF COAST TONIGHT...
...LITTLE TIME REMAINS TO PROTECT LIFE AND PROPERTY...


SUMMARY OF 100 PM CDT...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...27.3N 92.5W
ABOUT 200 MI...320 KM SSE OF LAKE CHARLES LOUISIANA
ABOUT 200 MI...320 KM SSE OF PORT ARTHUR TEXAS
MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...952 MB...28.11 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for...
* Freeport Texas to the Mouth of the Mississippi River

A Hurricane Warning is in effect for...
* San Luis Pass Texas to Intracoastal City Louisiana

A Tropical Storm Warning is in effect for...
* Sargent Texas to San Luis Pass
* East of Intracoastal City Louisiana to the Mouth of the
Mississippi River

A Storm Surge Watch is in effect for...
* Mouth of the Mississippi River to Ocean Springs Mississippi
* Lake Pontchartrain, Lake Maurepas, and Lake Borgne

A Hurricane Watch is in effect for...
* East of Intracoastal City to west of Morgan City Louisiana

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.  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.

A Hurricane Watch means that hurricane conditions are possible
within the watch area.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area.

For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.


DISCUSSION AND OUTLOOK
----------------------
At 100 PM CDT (1800 UTC), the eye of Hurricane Laura was located
near latitude 27.3 North, longitude 92.5 West. Laura is moving
toward the northwest near 16 mph (26 km/h). A gradual turn toward
the north-northwest and north is expected later today and tonight.
On the forecast track, Laura will approach the Upper Texas and
southwest Louisiana coasts this evening and move inland within
that area tonight. The center of Laura is forecast to move over
northwestern Louisiana tomorrow, across Arkansas Thursday night, and
over the mid-Mississippi Valley on Friday.

Reports from an Air Force Reserve Hurricane Hunter aircraft indicate
that maximum sustained winds have increased to near 140 mph (220
km/h) with higher gusts.  Laura is an extremely dangerous category 4
hurricane on the Saffir-Simpson Hurricane Wind Scale.  Some
additional strengthening is possible this afternoon, and Laura is
forecast to remain a category 4 hurricane through landfall tonight.
Rapid weakening is expected after Laura makes over land.

Hurricane-force winds extend outward up to 70 miles (110 km) from
the center and tropical-storm-force winds extend outward up to 175
miles (280 km). Tropical-storm-force winds have reached the coast
of Louisiana and an observing site at Eugene Island recently
measured sustained winds of 39 mph (63 km/h) and a gust to 64 mph
(104 km/h).

The latest minimum central pressure estimated from reconnaissance
aircraft data is 952 mb (28.11 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Laura can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

Storm surge and tropical-storm-force winds will arrive within the
warning areas well in advance of Laura's center. All preparations
to protect life and property should be rushed to completion in the
next few hours.

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 could
reach the following heights above ground somewhere in the indicated
areas if the peak surge occurs at the time of high tide...

Johnson Bayou LA to Rockefeller Wildlife Refuge including Calcasieu
Lake...15-20 ft
Sea Rim State Park TX to Johnson Bayou LA including Sabine
Lake...10-15 ft
Rockefeller Wildlife Refuge to Intracoastal City LA...10-15 ft
Intracoastal City LA to Morgan City including Vermilion Bay...8-12
ft
Port Bolivar TX to Sea Rim State Park...6-9 ft
Morgan City LA to Mouth of the Mississippi River...4-7 ft
Freeport TX to Port Bolivar including Galveston Bay...2-4 ft
Mouth of the Mississippi River to Ocean Springs MS including Lake
Borgne...2-4 ft
Lake Pontchartrain and Lake Maurepas...2-4 ft

The deepest water will occur along the immediate coast near and to
the right of the landfall location, where the surge will be
accompanied by large and destructive waves.

Unsurvivable storm surge with large and destructive waves will cause
catastrophic damage from Sea Rim State Park, Texas, to Intracoastal
City, Louisiana, including Calcasieu and Sabine Lakes. This storm
surge could penetrate up to 30 miles inland from the immediate
coastline in southwestern Louisiana and far southeastern Texas.

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 expected in the hurricane warning
area tonight and Thursday, with catastrophic wind damage expected
where Laura's eyewall makes landfall tonight. Tropical storm
conditions are moving onshore of the coast of Louisiana within the
tropical storm warning area and are expected to reach the coast in
the hurricane warning area later this afternoon or evening.

Hurricane-force winds and damaging wind gusts are also expected to
spread well inland into portions of eastern Texas and western
Louisiana early Thursday.

RAINFALL:  From this afternoon through Friday, Laura is expected to
produce rainfall totals of 5 to 10 inches, with isolated maximum
amounts of 15 inches across portions of the northwestern Gulf Coast
from western Louisiana to far eastern Texas, and northward into much
of Arkansas.  This rainfall will cause widespread flash and urban
flooding, small streams and creeks to overflow their banks, and
minor to isolated moderate freshwater river flooding.

By Friday into Saturday, Laura will produce rainfall totals of 2 to
4 inches, with isolated maximum amounts of 6 inches across the
mid-Mississippi and portions of the Lower Ohio and Lower Tennessee
Valleys.  This rainfall may lead to localized flash and urban
flooding and rapid rises on small streams.

TORNADOES:  A few tornadoes are expected this afternoon through
tonight over Louisiana, far southeast Texas, and southwestern
Mississippi. The risk for a few tornadoes should continue into
Thursday across Louisiana, Arkansas, and western Mississippi.

SURF:  Swells produced by Laura are affecting the entire U.S. Gulf
coast from the west coast of Florida to Texas and northeastern
Mexico. These swells are likely to cause life-threatening surf and
rip current conditions.  Please consult products from your local
weather office.


NEXT ADVISORY
-------------
Next complete advisory at 400 PM CDT.

Hourly Tropical Cyclone Updates will begin at 200 PM CDT.  These
can be found under WMO header WTNT63 KNHC and under AWIPS header
MIATCUAT3.

$$
Forecaster Brown
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