6pm…Windstorm Tonight?

January 16, 2006

Wow…I didn’t think this could happen twice in one winter.  One or two forecasters in town (including me) don’t think a storm is coming, but apparently everybody else does.  This time it’s wind, not snow.

The NWS has issued a High Wind Warning for the interior of SW Washington and NW Oregon.  That includes the Portland Metro Area.

The NWS criteria for a High Wind Warning for the metro area says winds must be sustained at 40mph or have frequent gusts to 58 mph.  They are forecasting gusts to 50 mph tonight.  They also figure they can lower the criteria since soils are so saturated from the rain lately and it’s easier for trees to fall (that part we HAVE seen the last few weeks).

KOIN & KGW are following suit and calling for a windstorm too.  Keep in mind the wind hasn’t gusted above 50 mph at PDX for 6 years!

I have no idea why they think winds will be this strong tonight.

Low pressure is moving onshore way too far north for high winds here (north of Vancouver Island).  No models show strong winds with the actual cold front passage tonight.  My reliable MM5 says gusts to 35 or so at best.

So I think southerly gusts 35 mph or so is the best we’ll do across most of the area…MAYBE 40 mph.

We’ll find out within the next 6 hours or so right?  The warning went into effect at 6pm.


Orographics & Rainfall

January 13, 2006

A nice and slow Friday evening weatherwise.   Last week at this time the weather was just beginning to get crazy.  But now we just have a lackluster cold front moving through.  Much cooler air comes in this weekend.  The moisture supply is pretty limited for Sunday even though the snow level will fall below 1500′.  So don’t get too excited.  But the skiing/snowboarding will be excellent with the fresh and dry powder.  Next week will be seasonally mild.  No sign of any major windstorms or cold weather.  The threat for a significant freeze (arctic air) ends in about 4 weeks in Portland.

I just received an e-mail today…someone wanted to know what OROGRAPHIC refers to in weather discussions.  TV weatherpeople usually to avoid words like that on the air.  Mainly because it tends to make our bosses a bit queasy and uptight…for good reason!   Apparently most viewers would be absolutely clueless as to the meaning of the word.  I agree.

Orographics refers to "orography" or the science of mountains.  As air moves into mountains it has to rise right?  It can’t go anywhere else.  And rising air cools, moisture condenses, and you get rain or snow.  At the very least you often get cloud cover.  So when air flows perpendicular to a mountain range, that’s the best set up for squeezing the maximum amount of moisture out of an airmass.

Apply that to the Northwest landscape and it’s pretty obvious what direction you want the winds in the atmosphere to flow from to get maximum mountain snow…Westerly.  The Cascade and Coast Ranges are oriented north/south, so the westerly flow at 2000′-6000′ runs right into them.  Southerly flow will often give the same rainfall totals for the valleys AND Cascades because the winds are running parallel to the mountains which isn’t very helpful for extra mountain rain.  By the way, easterly winds are great for certain spots too.  Hood River, The Dalles, Bend, Madras can all get soaking rains (heavy snow in winter) in the rare case where the airflow is coming in from the east.


Still Wet

January 12, 2006

A shorter post tonight…I’ve been getting a bit wordy lately.

Two main features tonight.  A nice little break coming up after Friday’s system.  We get 2, yes 2, days of showers & sunbreaks over the weekend.  850 mb temps fall down to -5 or even -6 Saturday night and Sunday AM.  That will easily bring snow down below 2000′.  Possibly as low as 1000′, but moisture supply will be going downhill by Sunday AM.  Then it’s back to a wetter westerly flow next week.

Notice the last 2 days of GFS have steadily gone away from any sort of cold air setup.  What a surprise!  It’s so unreliable in the long range, but I think the GFS has done a stellar job this winter in the 1-5 day timeframe.  So for you snow lovers, I don’t see any good pattern for arctic air or even real cold maritime airmasses to move into the Northwest.  We’ve got about 4-5 weeks left in which we could get a good cold air outbreak this winter.

Try to stay dry…Mark


A Brief Break & Sweaty Floors

January 11, 2006

All is well with the world again today…the sunshine was blinding between the showers, and temperatures were back down to reasonable for January (45-50).  That freakish warm stuff was gone.

Which brings me to sweaty talk.  No, you know what I mean…dewpoint & condensation talk.

Do you have a garage that isn’t very well insulated (or none at all like mine)?  Does it annoy you when you come out one morning in the wintertime (today!) and the whole floor is wet?  It sure annoys me.  Here’s why/how it happens:

1.  The cement cools down during a chilly spell, let’s say to 45 degrees.

2.  Then warmer air moves in, often right after a cool spell.  Air temp is 50-55, dewpoint is 50 (like yesterday).

3.  As soon as the warm air arrives and your cold cement floor is begins acting just like the tall cold beverage that gets all wet on the outside on a summer day.  Air in contact with the floor is cooling to the dewpoint temperature, which allows water vapor in the air to condense onto the floor.  That’s it, the floor suddenly turns wet.

4.  To dry the floor, you either need to warm the floor (heat the garage temporarily), or wait for the dewpoint outside to drop back down below the floor temp.  I’ve noticed just a change back to "normal" cool January weather (like tonight) takes care of the problem.  It’s always the worst right after a cold spell when we go into a warm/wet pattern.

Weatherwise tonight, we are in a break, but another system moves in tomorrow.  It’ll be pretty wet then through Friday, then showery/cool for the weekend.  Sunday morning the snow level may drop down as low as 1500′, but no lower.  Next week we stay with seasonably cool/wet weather.  No big warm ridge in sight OR big ridge offshore to channel dry arctic air towards us.  Notice even the bullish GFS has backed way off any sort of cold spell.  It seems to do that regularly each winter.


11pm…Quick Little Storm

January 10, 2006

Wow, that was fast, and not too wild tonight.  You can see the peak windspeeds below.  I couldn’t find anything above 41 mph.  I’m sure someone had a gust to 50 mph somewhere, but it looks like speeds were a little below what we saw New Year’s and Christmas mornings.  Now the weather slows down for the next 36 hours.   

That will give rivers time to recede a bit.The GFS has been messing around long-term with arctic air or at least cold enough air to bring snow to PDX, but as always it has warmed as we get closer to the "event".  BUT, ECMWF & GEM are falling into line with a series of colder troughs moving through the Northwest next week.  That will bring snow at times below 2000′. 

Snapshot_3


8:00pm…Windstorm Tonight?

January 10, 2006

I can’t believe it, I just composed a post on a busy weather night and it disappeared!  So let’s try again.

Morning model runs clearly didn’t catch a deeper-than-expected low moving inland over Astoria right now headed for Central Washington.  Similar to a January 1989 windstorm.  Within the next 2 hours as it passes by to the north it’ll be in a perfect spot to pull southerly winds straight up the valley.  Gusts at 8pm reached 39 mph here at our station, 38 at PDX and 36 at TTD.   With the warm airmass and good mixing in place, I think 50 mph gusts are likely 9pm-2am or so.  This may be the strongest wind so far this season in the metro area (at least southerly wind).


Stormy Night Ahead

January 9, 2006

Isn’t this great?  One system after another crashing onshore…ahh, the good old days (1970s) that I remember as a kid.  I used to actually go out in the farm fields where I grew up near Mt. Angel and play "flooding rivers" in the adjacent farmer’s field. I’d dam up the little furrows and then let all the water go, chasing it down to the creek.One system after another crashing onshore, some bringing strong winds to the Coast, some inland…Ahh the good old days are back again!  I’m sure the farmer appreciated the well-compacted field the next spring.

Okay, let’s pull it together and out of memory lane…I’m pretty much fully grown now and forecasting our stormy winter weather. 

As of 8pm:  Frontal system is hung up right over the top of us this evening, with tons of subtropical moisture streaming inland with it.  Snow levels are over 6000′ in the Oregon Cascades right now.  A strong wave, or area of low pressure that has been well progged by the models is riding along the front and should move inland somewhere between Astoria and Hoquiam around newstime (10pm) tonight.  It’s actually deepening as it moves onshore, so we should get quite a rush of south-southwest wind behind it.

Earlier today it looked like the path was Astoria-Yakima.  But now it’s more up towards Seattle.  This saves the metro area from damaging winds, but I still expect strong gusty wind between 11pm-2am.  Probably no stronger than gusts to 40 mph unless the low deepens rapidly the next 3 hours.  From Kelso-Olympia I think 50-55 mph is quite likely.  Either way a rainy and windy night ahead.

Lots of flood warnings coming in the next 24 hours, but with a quickly dropping snow level tomorrow, we should avoid big trouble.  A similar episode to last week’s flooding.

We (meteorologists) are being hampered by several offshore buoys out of service.  This is one area where we are somewhat blinded and have to rely on models and 3 hour pressure fall maps.  The maps tell us which part of the coast has the fastest falling pressure, which generally indicates where a low is heading.  Someone asked about "exploding buoys".  Here is a link to a NWS warning about those buoys.  http://www.ndbc.noaa.gov/hydrogen_hazard.shtml

Cooler weather coming up Wednesday-Thursday, but still no sign in RELIABLE long range models of any really cold weather here in the metro area.  GFS is doing it’s usual now-you-see-it-now-you-don’t, but I’ll discount that for now since ECMWF & CANADIAN are milder next week.

Oh, and for you BSG Fans…sorry, it’s Admiral, not Commander Cain.  I was 27 years behind…Mark