hurricane laura briefingflooding well before laura makes landfall. look for a rapid spike in water...

HURRICANE LAURABRIEFING

www.weather.gov/Houston

Wednesday August 26th

@NWSHouston

10:30 AM CT

Prepared by: Dan Reilly, WFO Houston/Galveston

Changes: Laura now forecast to be a category 4 at landfall (is a Cat 3 now). More confidence in a

track from Sabine Pass up near the LA/TX border. Still impacts across SE Texas but not as severe as

near and right of center track. Deadly winds, surge forecast for those areas.

8/26/2020 11:22 AM www.weather.gov/Houston

Houston/GalvestonWEATHER FORECAST OFFICE

Current Satellite ViewHurricane Laura

▪ Laura a Category 3 major hurricane. Forecast to

intensify further before landfall (to Cat 4).

▪ Landfall near Sabine Pass or far SW Louisiana coast

is likely.

▪ Extremely dangerous, deadly storm surge flooding

is expected near and right of landfall location. Very

dangerous, damaging winds also expected near the

center path and extending well inland.

▪ SE Texas will be on the western fringe of the storm.

Main impacts will be tropical storm force winds,

possibly gusts to hurricane force eastern zones.



NOTE: Do not focus on the exact track. Impacts can occur well outside the area

enclosed by the cone.

▪ Max sustained winds currently 125 mph.

▪ Forecast to intensify to 145 mph gusting to 170 mph

(category 4) before landfall.

▪ Note forecast track cone centered around TX/LA

border as it tracks north tonight.

▪ Impacts felt well outside the cone, especially on the

right hand side.

▪ Center will track within the cone on average 2/3 of

the time.

Situation OverviewHurricane Laura



Hurricane Warning shown in red.

Tropical Storm Warning shown in darker

red.

Wind Related Watches and WarningsHurricane Laura

Hurricane force sustained winds expected

in the hurricane warning area (sustained

74+ mph with higher gusts). Peak 170 mph

gusts near landfall..

Tropical storm force winds expected in

the TS warning area (39 to 73 mph)

Note wind threat extends well inland!



▪ Storm surge warning shown.

Extends from Sargent TX up the

coast.

▪ Danger of life-threatening inundation

from storm surge somewhere in the

warned area.

▪ Forecast values have been shaded

down for Galveston Bay, Island and

points SW.

▪ Coastal Flood Advisory for

Matagorda and around Matagorda

Bay.

Storm Surge Watch/WarningHurricane Laura



▪ Flash Flood Watch to

the east of the forecast

area.

Flash Flood WatchHurricane Laura



Threat Levels (Assuming Direct Hit)Hurricane Laura

Wind Surge Rainfall/

Flash FloodingTornadoes

Incre

asi

ng T

hre

at For information on

specific hazards in

this area, please go

to https://www.weather.

gov/srh/tropical?office

=hgx

River

FloodingMarine

https://www.weather.gov/srh/tropical?office=hgx



50kt Wind Speed ProbabilitiesHurricane Laura

▪ Point probabilities of 58 mph

sustained winds over the next 5

days are shown for Laura.

▪ Axis of highest values Upper TX

coast, East TX and SW LA and

points well inland.

▪ Still some uncertainty in track and

intensity, but confidence

increasing.



Hurricane Wind Speed Probabilities

▪ Point probabilities of hurricane

force sustained winds over the

next 5 days are shown for Laura.

▪ Still uncertainty in track and

intensity but highest values

focussed on Upper TX coast and

SW LA.

▪ This pattern would shift if Laura

were to take a more westerly

track.

Hurricane Laura



▪ Most likely arrival time of TS winds

from Laura would be Wednesday

evening.

▪ Recommend Hurrevac tool (HVX) for

emergency managers to show wind

timing for your area

Most Likely Time of ArrivalHurricane Laura



▪ General view of storm surge

expected from Laura for different

stretches of coastline.

▪ Very dangerous life threatening surge

expected near and right of hurricane

track.

▪ Water level rises begin on

Wednesday. More rapid rise

Wednesday night as storm

approaches the coast.

Storm Surge Flooding ForecastHurricane Laura



▪ Reasonable worst case depth of water

above ground for storm surge flooding,

inundation from Laura.

▪ New versions of these released about

one hour after advisory time. View at

hurricanes.gov or in hurrevac (HVX).

▪ Water level rises begin on Wednesday.

More rapid rise Wednesday night.

Note: This graphic shows where storm surge inundation could occur in any one location.

It depicts a reasonable worst case scenario.

Potential Storm Surge FloodingHurricane Laura



Note: This graphic shows where storm surge inundation could occur in any one location.

It depicts a reasonable worst case scenario.

Potential Storm Surge FloodingHurricane Laura

8/26/2020 11:22 AM www.weather.gov/houston


SeasHurricane Laura

Friday High Temperatures

❑ Large swell will rapidly fill in across the Upper Texas Coast through the day and tonight. ❑ Onset of seas =/> 6 feet within 60 NM: This morning. ❑ Peak seas 15-25 feet in the waters south of Galveston tonight…25-35+ feet east of the center.

7 am CDT Today 7 pm this evening Thursday evening

https://www.nhc.noaa.gov/marine/forecast/enhanced_gom.php



Forecast tide levels from

Extratropical Surge Model

Top chart relative to mean

higher high water (NWS

standard)

Bottom chart relative to Mean

Lower Low Water; different

datum, still used by many EMCs.

Note higher tide levels due to

swell, wave effects with high

tide tonight for Gulf side.

Forecast tide levels from

Extratropical Surge Model

Top chart relative to mean

higher high water (NWS

standard)

Bottom chart relative to Mean

Lower Low Water; different

datum, still used by many EMCs.

Note higher tide levels due to

swell, wave effects with high

tide tonight for Bay side, south

and east facing coastal areas.

8/26/2020 11:22 AM www.weather.gov/houston


Elevated surf & wave run-up

❑ A large swell will build in through the day and tonight. Expect large breaking waves and run-up along area beaches today.

❑ Combination of the run-up and initial increase of surge could cause coastal flooding well before Laura makes landfall.

❑ Look for a rapid spike in water levels and potentially life threatening coastal flooding headed in the evening and overnight hours. This is when Laura will be making approaching the coast, when high tide will occur, when the largest surf will occur and the time of greatest storm surge.

❑ Dangerous rip currents are expected along area beaches. Recommend staying out of the water.

❑ Waves may break over rock groins and jetties. People should not even venture onto them. Conditions may appear safe from a distance, but “surprise” much higher waves can emerge in these circumstances.

Hurricane Laura

http://www.srh.noaa.gov/hgx/?n=beach_webpage

http://www.srh.noaa.gov/hgx/?n=beach_webpage



▪ Storm Total rainfall forecast

valid Wednesday through

Sunday

▪ Locally, most rain will occur

Wednesday and Thursday

Expected Storm Total RainfallHurricane Laura

Note: There will likely be locally higher amounts



▪ Flash flood risk shown

for Laura.

▪ Greatest risk in yellow

and red areas.

▪ A more westward

track would increase

the Flash Flood Risk in

our area.

Excessive Rainfall OutlookHurricane Laura



▪ Main threat of tornadoes would

be from (day) (timing) to (day)

(timing)

Tornado PotentialHurricane Laura



• Deadly storm surge expected near and east of the track, mainly from Sabine Pass eastward. Extremely

dangerous winds as well near the enter track. For SE Texas main impacts will be TS force winds, some hurricane

force still possible eastern zones.

• There will still be high surf and tides left of the track due to the waves, swell, high surf coming in from Laura.

• Flash flood threat mainly east of the area, closer to the track of the hurricane.

• Hurricane, Tropical Storm and Storm Surge Warnings remain in effect for parts of the area. Far west zones the

least impacted (farthest from track). Some of those warnings may be trimmed back later today.

Key Take-Aways, ChangesHurricane Laura

Confidence is high that a major hurricane will strike far

East TX and Western LA. Deadly storm surge and winds

in those areas. For Southeast Texas, TS-force winds and

high surf, tides. Hurricane force winds (especially gusts)

still possible eastern zones.

www.weather.gov/Houston@NWSHouston

The Next Advisory: Tuesday at 10 PM CDT. Next webinar Tuesday 1030 pm.

For the latest graphics and information go to: www.hurricanes.gov or weather.gov/srh/tropical?office=hgx

Web: http://weather.gov/houston

Phone: (281)337-5074

E-mail: [email protected]

Facebook: NWSHouston

Twitter: @NWSHouston

YouTube: NWSHouston

http://www.hurricanes.gov/

https://weather.gov/srh/tropical?office=hgx

hurricane laura briefingflooding well before laura makes landfall. look for a rapid spike in water...

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