Pacific NW August 2014 Discussion

[BLI snowman]

Why the cap? Doesn't offshore flow usually help overcome that?

 

Capping inversion

 

http://www.theweatherprediction.com/habyhints2/405/

[Deweydog]

102 at Kelso (!!). 93 at PDX. Slackers.

12-1-07.

[Deweydog]

It would be nice if every GFS solution wasn't wildly different than the one before.

Why?

[Jesse]

Capping inversion

 

http://www.theweatherprediction.com/habyhints2/405/

 

For some reason I was under the impression that onshore flow (in our region) was more troublesome for thunderstorm development that offshore. But in this case I now understand how offshore flow is likely an inhibitor, downsloping being the main issue.

[Jesse]

Why?

 

Because I want to know what's going to happen next!!!

[Deweydog]

Because I want to know what's going to happen next!!!

The second half of August will be cooler than the first. There ya go.

[Jesse]

The second half of August will be cooler than the first. There ya go.

 

Wouldn't take much.

[Deweydog]

Wouldn't take much.

Maybe it'll be a lot! (Probably not)

[Jesse]

Maybe it'll be a lot! (Probably not)

 

[Jesse]

Looks like 99 so far at PDX.

[BLI snowman]

12-1-07.

 

99. Oh noz! Wrongness all around!

[Deweydog]

99. Oh noz! Wrongness all around!

 

They could pop to 102... next July.  

[Deweydog]

Gonna be a warm night.  

[BLI snowman]

For some reason I was under the impression that onshore flow (in our region) was more troublesome for thunderstorm development that offshore. But in this case I now understand how offshore flow is likely an inhibitor, downsloping being the main issue.

 

To my understanding, on a day like today the capping inversion is mostly just present during the peak daytime heating hours, when there's a slightly warmer elevated layer that reduces the lapse rates and produces what's known as CINH (convective inhibition). On really hot days like today with the extreme warmth aloft, there's a larger inversion. That naturally will reduce at a point in the evening hours as the boundary layer begins to decouple, before things stabilize again late in the night.

 

Offshore flow is still optimal for our region's thunderstorm outbreaks, btw. SSE flow aloft is always ideal.

[BLI snowman]

They could pop to 102... next July.  

 

Nah, July is like January. Ain't what it used to be.

[Jesse]

Gonna be a warm night.

Will we finally break the long-standing record of 69 set on 8/11/14?

[Jesse]

Nah, July is like January. Ain't what it used to be.

Give me our 4th coldest January in history this year and I won't complain too much.

[Deweydog]

To my understanding, on a day like today the capping inversion is mostly just present during the peak daytime heating hours, when there's a slightly warmer elevated layer that reduces the lapse rates and produces what's known as CINH (convective inhibition). On really hot days like today with the extreme warmth aloft, there's a larger inversion. That naturally will reduce at a point in the evening hours as the boundary layer begins to decouple, before things stabilize again late in the night.

 

Offshore flow is still optimal for our region's thunderstorm outbreaks, btw. SSE flow aloft is always ideal.

 

That's kind of misleading, though.  Typically people associate offshore flow with offshore surface gradients.  It's incredibly rare to unheard of for the westside to see storms when an actual inverted thermal trough is positioned on the westside/coast.  

[Deweydog]

Will we finally break the long-standing record of 69 set on 8/11/14?

 

No.

[BLI snowman]

That's kind of misleading, though.  Typically people associate offshore flow with offshore surface gradients.  It's incredibly rare to unheard of for the westside to see storms when an actual inverted thermal trough is positioned on the westside/coast.  

 

Well there are varying degrees of what quantifies as "offshore flow", but the pressure gradients aloft are most telling. The 500mb details are obviously more important than anything else. The ideal convective setup is pretty consistent around here and often follows a period of strong offshore surface gradients, but you're right that they're rarely simultaneous. 

[Deweydog]

It's 95 degrees and raining. Weird.

[Jesse]

To my understanding, on a day like today the capping inversion is mostly just present during the peak daytime heating hours, when there's a slightly warmer elevated layer that reduces the lapse rates and produces what's known as CINH (convective inhibition). On really hot days like today with the extreme warmth aloft, there's a larger inversion. That naturally will reduce at a point in the evening hours as the boundary layer begins to decouple, before things stabilize again late in the night.

 

Offshore flow is still optimal for our region's thunderstorm outbreaks, btw. SSE flow aloft is always ideal.

Thanks, that makes sense. Seems like SSE flow aloft with offshore gradients switching to onshore at the surface is our best combination for convection. The switch to onshore is generally a trigger but convective events are often directly preceded by offshore flow at the surface.

[Tyler Mode]

93 and it's raining...just about as insane as I've seen here lol

[Jesse]

Wind has switched to light westerly out here.

 

Hit 100 earlier, down to 94 now.

[Jesse]

It would be awesome if some of that action over northern Deschutes and south-central Jefferson County would move up this way.

[Deweydog]

Well there are varying degrees of what quantifies as "offshore flow", but the pressure gradients aloft are most telling. The 500mb details are obviously more important than anything else. The ideal convective setup is pretty consistent around here and often follows a period of strong offshore surface gradients, but you're right that they're rarely simultaneous. 

 

Absolutely.  Diffluent, SE'erly 500mb flow is optimal.  It just happens that thermal troughs, not coincidentally, don't survive on the westside during that kind of pattern.  You need a shitload of subsidence or a relatively cool continental air mass to make it happen and neither situation is good for convection.  This is why the situation back in July didn't pan out as a heat/storms/heat scenario.  It just doesn't happen.  

[brody]

Rapid develp. of a cell just N of Mt Rainier right now.

 

Meso data is looking good

 

Li's esp. around the Willamette valley are -7C right now and CAPE in that same area is over 2000J/Kg

 

BK shear is on the order of 40 kts over SW Wa and extreme NW Ore.

 

I would expect further develp. as the night progresses

[TT-SEA]

Hearing distant thunder now. Skies very dark.

[brody]

Hearing distant thunder now. Skies very dark.

See my post above Tim

[TT-SEA]

Lots of lightning here now. Very warm still. Reminds me of the Midwest.

[brody]

Lots of lightning here now. Very warm still. Reminds me of the Midwest.

CC, CG?

[Deweydog]

0z is quite impressive for tomorrow afternoon/evening.  

[TT-SEA]

Crazy storm passing to my south. Tons of lightning and now a hot wind blowing.

[TT-SEA]

Never felt such a hot wind with a thunderstorm here. Temp must have jumped 10 degrees or more.

[BLI snowman]

Never felt such a hot wind with a thunderstorm here. Temp must have jumped 10 degrees or more.

 

Heat burst? 

[TT-SEA]

Heat burst? 

 

 

Maybe.

[BLI snowman]

Nice lightning at the Mariners game.

[Jesse]

Slim pickins down here tonight.

[Tyler Mode]

Just a few bolts off to the east so far...

[Deweydog]

Slim pickins down here tonight.

 

WRF really took the balls out of anything over the next 24 hours, although tomorrow evening looks extremely wet.  Hard to know if that should be taken seriously though...