August 2017: Looking Back at Harvey 5 Year Later

[Rip76]

0z's are what time?

10:30 PM= GFS
1:00 AM = ECMWF

Ok, thank you.

[mcheer23]

18z GFS...Here comes Harvey moving back toward the gulf Hour 168

[Scott747]

Something to keep in mind.

I don't think the 12z or 18z runs had any of the new upper level data ingested. Mission is still in progress and should be in the 0z runs. It was highlighted in the 4pm disco. Runs tonight will confirm if today's trend is real.

Yes, indeed. The 0z runs tonight will be pretty important.

It's a ridiculously complicated forecast and there is no question the trend has been further down the coast today. Still could easily change and with the potential heading and orientation of the coast it wouldn't take much to slide it back further up the coast.

Let's just say that even with the change in the models today, we have barely adjusted our chase target. No intent on adjusting till the 0z runs.

[jasons2k]

Yeah, so in one run I went from 20" of rain to about 3" of rain. Wait and see for now.

Also monitoring for a possible center relocation to the NE. Could be due to a band of some shear.

[Cromagnum]

[DoctorMu]

Naval and CMC headed from flood to semi-bust in CLL. GEFS ensemble still sticking with nearly a foot of rain...so tonight's runs will be interesting indeed. We won't be far from nowcasting soon!

[Texaspirate11]

Naval and CMC headed from flood to semi-bust in CLL. GEFS ensemble still sticking with nearly a foot of rain...so tonight's runs will be interesting indeed. We won't be far from nowcasting soon!

I for one would not mind it being a semi-bust or just a really bad joke Mother Nature played on us.

[Rip76]

I think I see a NW movement resuming.

[brooksgarner]

Remember, the models are going to be drunk for the next few days... Just expect bad rain and potential wind. Anything else is pure guessing... even with the flights feeding computer models with data, beyond thinking it'll move into the Coastal Bend, there's no way to forecast a loop-the-loop scenario accurately.

Best case scenario is that .... oh wait ... there is no best case scenario. If it misses Houston, it'll inevitably hit someone else and bring a world of rain (and maybe wind.)

This is going to be a trying week, answering the same questions with the same answer ("watch/wait") every day.

[ajurcat]

Thank you and best of luck these next few days. Hope you can live off cat-naps!

[Andrew]

Heavy raining and flooding WILL occur, the key is will it happen over SE Texas, Southern Texas, South Central Texas, or even Louisiana. Models are at a little bit of a split right now on how far west it pushes after making landfall. Unfortunately this will always be the case when steering breaks down.

[stormlover]

Andrew, what is ur gut telling you, does the Ukmet and EURO win this battle?

[TexasBreeze]

If it really ramps up, I could see it going up the coast more. The weaker, the more sw.

[srainhoutx]

Wednesday evening briefing from Jeff:


Weak Hurricane or strong tropical storm heading for the TX coast

Preparations to protect life and property should be underway in the hurricane and tropical storm watch areas

Potentially dangerous and life threatening flood and flash flood event for a large portion of coastal, SC, and SE TX

Discussion:

Harvey has moved little today based on USAF mission fixes and has shown very little increase in organization. While the surface circulation appears to be becoming better defined, the convective pattern has been sporadic and disorganized and there are few banding features. Some of the “slowness” on the organization is likely the NNE extending trough axis that is elongating the circulation some and spreading out the deeper convection reducing the organization near the center. Additionally, dry air is lurking just west of the center and some of this may be intruding into the circulation helping to cut down on organization.

Track:

Forecast track models continue to move Harvey toward the NW and NNW with a landfall along the lower to middle TX coast between Corpus and Matagorda Bay Friday evening. There is a general decent consensus on this track reasoning although there has been some development of model spread today compared to yesterday. Near and after landfall the steering flow collapses and Harvey is left to meander near/just inland of the coast around the coastal bend region. Harvey will find itself in a region trapped by building high pressure to the NW of TX and over the central Gulf of Mexico and a weak trough extending into E TX from the NE US. Models have shown more of a gradual loop today with the system moving W on Saturday and then S and then E by Sunday/Monday and nearly back to where it makes landfall on Friday night. For now will not go with as of dramatic of westward loop and instead slow the system and meander it slowly E to ESE near/around the Matagorda Bay/coastal bend Saturday, Sunday and Monday before a slightly faster E/ENE motion may develop by next Tuesday.

It is possible that Harvey could also stall very near the coast which would limit the amount of weakening to a degree.

Intensity:

Not expecting much organization of the system over the next 12 hours as conditions aloft gradually become better and Harvey attempt to form a more defined inner core area. On Thursday Harvey should begin to gradually intensify as it moves across 85-88 degree water temperatures and a “deep” warm eddy over the WC Gulf that broke off the Gulf stream. As Harvey nears the coast (within 18-24 hours of landfall or Friday) conditions look to become extremely favorable for intensification. In fact the latest SHIPS intensity guidance shows a 62% chance of rapid intensification, which is why it is vitally important that Harvey moves inland before slowing and stalling.

Current NHC forecast brings Harvey to a minimal hurricane just before landfall, and the intensity trend on Friday will need to be monitored extremely closely as the system nears the coast.

Impacts:

Rainfall:

Rainfall amounts of 10-15 inches over a very large area will be possible with isolated totals of 20 inches or more. Where these significant heavy rains fall potentially extends from SW LA to SC TX and S TX.

Flooding is a very real and great concern with Harvey and preparations should factor this potential

Flash flood watches will be required over the next 24-36 hours.

Storm Surge:

Coastal water level rises of 4-5 feet will be possible in the storm surge watch area. Latest NHC inundation graphic shows little above ground flooding from tides/storm surge except in the tidal marshes around Matagorda and Galveston Bays and in the tidal zones and bay around Corpus north to Seadrift.

See link for interact storm surge inundation mapping

http://www.nhc.noaa.gov/refresh/graphic ... n#contents

Coastal water levels will begin rising Thursday afternoon as larger swells begin to arrive on the TX coast. Expect tides to reach some dune lines late Thursday and then more widespread coastal flooding conditions Friday into Saturday…but still mainly in the marsh areas and the lowest most vulnerable areas.

One aspect to consider is that as Harvey stalls it will keep a strong onshore wind flow in place through the weekend and tides will be very slow to recede

Winds:

Tropical Storm force winds will spread into the coastal bend region early Friday and into the Matagorda Bay area Friday afternoon and then possibly as far NE as Galveston Bay Friday night. Hurricane conditions will move into the coastal bend region from Port Aransas to Matagorda Bay Friday night and continue into Saturday morning and spread inland across the current Hurricane Watch area counties. Think Matagorda County may see gusts to hurricane force and this is less likely in Brazoria County even though they are in the hurricane watch area. With very favorable conditions aloft, Harvey will only slowly spin down once inland and hurricane conditions will be possible 1-2 counties inland over SC TX on Saturday which is why the hurricane watch included those inland areas. Tropical storm conditions will be possible along much of the upper TX coast Saturday and inland across portions of Harris, Austin, Fort Bend, Wharton, and Colorado Counties.

Winds across Calhoun, Aransas, Refugio, and San Patricio counties will be the strongest Friday night (sustained 70-80 with gust to 85)

Actions:

Enact your flood and hurricane plans.

Be prepared for a prolonged multi-day event especially with heavy rainfall and flooding that could last well into next week

Power outages will be possible especially in the Matagorda Bay and coastal bend region where hurricane conditions are most likely

Some damage to roofs, windows, vegetation, and mobile homes will be possible in the coastal bend and Matagorda Bay region where hurricane conditions will be felt.

Be prepared for travel disruption across the entire region from late Friday into early next

[Rip76]

Now..... we wait.

[Andrew]

Andrew, what is ur gut telling you, does the Ukmet and EURO win this battle?

Think landfall 50 miles north or south of Corpus is most likely. I think progression westward will be overdone though and a northeast movement will eventually take place. Don't see how many people avoid at least 5-7 inches of rain but we could see a rather dramatic gradient locally. For those further south and along the coastline though it is hard to not see them getting 10+ inches. Plus I expect a hurricane to impact the coastline so the Corpus area could see the worst of both worlds.

[stormlover]

gotcha!!!! so ur line of thinking is euro/UKmet mixed together?

[Andrew]

gotcha!!!! so ur line of thinking is euro/UKmet mixed together?

Yes to a certain degree but we will what the models do tonight.

[DoctorMu]

Harvey may not be moving or revving up much yet, but the frontal boundary is. Rain and storms formed over a Seguin/Somerville/College Station/Madisonville line and moving south towards a meet and greet with Harvey..

[DoctorMu]

https://earth.nullschool.net/#current/w ... 690,29.970