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BULLETIN
Hurricane Laura Advisory Number  28
NWS National Hurricane Center Miami FL       AL132020
400 PM CDT Wed Aug 26 2020
 
...WIND AND WATER LEVELS INCREASING AS EXTREMELY DANGEROUS 
HURRICANE LAURA TAKES AIM AT THE NORTHWEST GULF COAST...
...CATASTROPHIC STORM SURGE, EXTREME WINDS, AND FLASH FLOODING
EXPECTED ALONG THE NORTHWEST GULF COAST TONIGHT...
 
 
SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...27.9N 92.8W
ABOUT 155 MI...250 KM S OF LAKE CHARLES LOUISIANA
ABOUT 155 MI...250 KM SSE OF PORT ARTHUR TEXAS
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...947 MB...27.97 INCHES
 
 
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
 
The Storm Surge Watch has been discontinued east of the Mouth of
the Mississippi River, including Lake Pontchartrain, Lake
Maurepas, and Lake Borgne.
 
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 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 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 400 PM CDT (2100 UTC), the eye of Hurricane Laura was located 
near latitude 27.9 North, longitude 92.8 West. Laura is moving 
toward the northwest near 15 mph (24 km/h).  A turn toward the 
north-northwest and north is expected tonight, and a northward 
motion should continue on Thursday.  A northeastward to east- 
northeastward motion is expected Thursday night and Friday.  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 the maximum sustained winds have increased to near 145 mph (230 
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 evening before Laura 
reaches the northwest Gulf coast overnight.  Rapid weakening is 
expected after Laura moves inland.
 
Hurricane-force winds extend outward up to 60 miles (95 km) from the
center and tropical-storm-force winds extend outward up to 205 miles
(335 km).  
 
The latest minimum central pressure reported by an Air Force 
Reserve reconnaissance aircraft is 947 mb (27.97 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...1-3 ft
Lake Pontchartrain and Lake Maurepas...1-3 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 surge 
could penetrate up to 40 miles inland from the immediate coastline, 
and flood waters will not fully recede for several days after the 
storm. 
 
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 moves onshore tonight. Tropical storm 
conditions are moving onshore along the coast of Louisiana within 
the tropical storm warning area and are expected to spread 
northwestward within the warning areas this 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 the following rainfall totals:
 
Across the northwestern Gulf Coast from far southwest Louisiana and
the Golden Triangle of Southeast Texas: 8 to 12 inches with isolated
totals of 18 inches.
 
Across central and the rest of western Louisiana into far eastern
Texas: 5 to 10 inches with isolated totals of 15 inches.
 
Across much of Arkansas: 3 to 7 inches with isolated totals of 10
inches.
 
This rainfall will cause widespread flash and urban flooding, small
streams and creeks to overflow their banks, and minor to moderate
freshwater river flooding.
 
By Friday into Saturday, Laura is expected to produce the following
rainfall totals:
 
Across the mid-Mississippi and portions of the Tennessee Valley,
Lower Ohio Valley, and central Appalachians: 2 to 4 inches with
isolated maximum amounts of 6 inches.
 
This rainfall may lead to flash and urban flooding and rapid rises
on small streams.
 
Across the Mid-Atlantic Region: 1 to 3 inches.
 
TORNADOES:  Several tornadoes are expected late this afternoon
through tonight over Louisiana, far southeast Texas, and
southwestern Mississippi. The risk for a few tornadoes will continue
into Thursday across Louisiana, Arkansas, and western Mississippi.
 
SURF:  Swells produced by Laura are affecting the 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 intermediate advisory at 700 PM CDT.
Next complete advisory at 1000 PM CDT.

Hourly Tropical Cyclone Updates will be issued between Public 
advisories.  These can be found under WMO header WTNT63 KNHC and 
under AWIPS header MIATCUAT3.

 
$$
Forecaster Brown
 
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