Labor Day Weekend Is Here

August 31, 2012

You can’t ask for a better holiday weekend than this…sunny or mostly sunny skies.  High temperatures in the comfortable 75-80 degree range too.

No matter where you are headed in the Pacific Northwest you’ll find nice weather.  Even the ocean beaches will only see spots of morning clouds.

The weather pattern remains very stable over the upcoming week with upper-level ridging building a bit over the West Coast.  It won’t be a big hot ridge for at least the next week, but enough to keep us mainly cloudless through the first week of September.  Of course it is way too early to know if we have a very warm September on the way.  Remember that last September was the 2nd warmest on record here in Portland.

Of course we are also wrapping up a rainless August in most of the Willamette Valley…quite unusual.  We’ve only seen 4 completely dry Augusts (only a trace of rain), the last one in 1998.  Today is our 41st day without measurable rainfall, but Salem can beat that.  The last day it rained in Salem was July 3rd!  Saturday will be day 60 without rain.

Chief Meteorologist Mark Nelsen

Peak Tropical Storm Season

August 28, 2012

We are in the peak of the storm season now for hurricanes and tropical storms.   About 1/3 of all named storms each season occur in September. 

So why no hurricanes on the West Coast?  Too cold…the ocean that is.  You need 80 degree or warmer ocean water to keep a tropical cyclone going.  On our side of the continent you have to get down around Cabo San Lucas in Baja California before you find water that warm.  Lots of storms and hurricanes form each summer off the coast of Mexico, but they quickly die as they head north into the colder ocean water.  If a storm is very strong and shoots north very quickly, it CAN make it to Los Angeles or San Diego.  It happened once during the .20th century, the 1939 Long Beach Hurricane.  At landfall it was just a tropical storm.

It’s a different story on the east side of North America.  The warm Gulf Stream ocean current pushes 80 degree water up around Chesapeake Bay in the late summer, allowing storms to move much farther north.

Our weather here in the Pacific Northwest?  Dullsville…

Our chance for showers tomorrow looks quite small as an upper-level disturbance moves by to the north.  If so, then PDX will probably end up dry for the month of August.  Shooting from the hip now, I think we’ve only had a dry August 4 times in our history here.  Usually SOMETHING slips in near the end of the month.  Plus, looking ahead, models are dry and a bit warmer than normal as we head into early September.  Keep watering!

Chief Meteorologist Mark Nelsen

Watch Out! Chance for Showers Next 3 Days

August 26, 2012

Don’t stain your deck, paint outdoor furniture, or leave hay on the ground in Western Oregon or Western Washington after this evening for a few days.  And if your kids start school tomorrow (mine do), it might be a slightly drippy and definitely gray start to the school year.

This evening through Wednesday morning is one of those periods where we have a slight chance for showers, but very little actual rainfall.  If it was spring and we had been wet for the past two weeks we’d say “MOSTLY DRY”.  But since we haven’t had rain in over a month, any sort of rainfall is somewhat exciting I suppose.

Check out the rain forecast from the UW-WRFGFS model from 5pm tonight to 5pm Monday:

Note that no one east of the Coast Range (where most of us live) is forecast to see more than .10″ (not even a soaking), but as a dying front moves inland tonight we could see sprinkles or light showers.  This is not a thunderstorm pattern, just the usual dribbles…and many of us will just remain dry

Here is our RPM model forecast of rainfall for the next 72 hours:

It is similar with very light amounts, mainly late tonight and early tomorrow morning. 

The next 3 days will definitely feel like September again after a brief return of summer yesterday.  But the main point here is that if you occasionally live a bit of “Whiskey Tango” in your front/back yards with all sorts of stuff lingering outside during the dependable dry weather of mid-summer?  It’s time to clean up the place!  I’ll be doing that later today along with you.

Chief Meteorologist Mark Nelsen

Wake Up…It’s Cold Outside!

August 24, 2012

Whew, I bet it feels like Fall out there this morning once you step outside.  Temperature across the entire Portland/Vancouver Metro are in the 40s!  Even PDX has made it down to at least 50 degrees.  Your tomatoes aren’t going to like it.  We had dry air, clear skies, and now the increasingly long night hours as we head towards September.  The three added up to our coldest night for most areas since mid June.  Fall can’t be far away, and the weather maps continue to look like Fall.

The cooler than average weather is going to continue, with one summery day on Saturday thrown into the mix.

Today we’ll see plenty of sunshine since the low clouds appear to be a bit scattered and they are moving more north to south versus onshore from west to east.  But with the chilly start we’ll only be in the 70s this afternoon.

Tomorrow we get nice offshore flow, which shows up well on the WRF-GFS 12km cross-section:

See the wind barbs at 12z on 25th (5am Saturday) are easterly from about 1,000′ up to 4,000′ or so.  It’s still summer, so that allows our temperature to jump well into the 80s.  Sunday should be okay too, although it’s been a question mark since the ECMWF has been shoving an upper-level trough closer to us a bit more quickly.  No other model has been doing so.  If we get lucky then, one more nice day Sunday, just significantly cooler with no offshore flow.

Alright, then we’re going to continue with cooler than normal temps again because upper-level troughing will linger through the foreseeable future.  Heres the ensemble forecast of 500mb heights from the GFS from last night’s 00z run:

then next Wednesday, the 29th with the ECMFW ensembles:

then 10 days out, Sunday of Labor Day weekend, the trough is still there!

The main message?  We have returned to the weather pattern we saw the first half of the summer; cooler and cloudier than normal.  So what about rain?  An upper level trough or a series of them nearby should give us rain at some point in late August.  Models have been slow to push any rain into here.  The GFS has been hinting at some light shower either Monday or Wednesday.  The ECMWF points to later Tuesday or Wednesday.  We’ll see.

By the way, I’m headed home today after a good 3 day weather conference in Boston.  Last night was fun at Fenway Park…perfect weather.  Learned lots about the weather and broadcasting world…I’ll do a posting on that next week.  Enjoy the weekend!

Chief Meteorologist Mark Nelsen

A Cool End To August

August 21, 2012

Today was a cool day, with high temps only in the mid 70s in the metro area.  We haven’t been this cool in about two weeks.

Get used to it, all models tell us that we are set for a pretty long period of cooler than average temperatures.  Here are two examples showing the temperature around 5,000′ elevation (celsius) from the ECWMF and GFS models.  They both show the numerous runs of each model (ensembles) with each run out to the next 14-16 days shown as a black line.  The thick green line is the average for this time of year.  The red is the average of all the ensembles (the black lines).

First, the ECMWF:

Then the GFS:

Several things stick out; most obvious is the nearly unanimous agreement by the GFS ensembles that we are entering at least a 10 day period of cooler than average temps.   But the ECMWF isn’t quite as sure, showing huge variation (from hot to chilly) beginning this weekend. 

What does look  extremely unlikely over the next week is real hot weather or a bunch of rain.  So the boring summer weather will continue, but the lightning over the weekend was interesting at least.

I’m at the yearly American Meteorological Society Broadcasters Conference this week.  This year it’s in downtown Boston, a real historic place. 

Today was a training day by our weather graphics vendor, WSI.  They are located up in Andover, Massachusetts.  A very green place, but they drive like crazy people.

This evening included a walk over to that great piece of American history…Cheers, the bar of 1980s sitcom fame.  The outside looks the same, but definitelydifferent on the inside.  The TV show only used the outside shots, none inside.

Tomorrow the conference begins and it goes through Friday.

Chief Meteorologist Mark Nelsen


Lots of Lightning East Metro & Western Gorge

August 19, 2012

If you were up from 1am-3am, you likely saw lots of flashing on the east side of the metro area.  You probably slept through it if you live west of I-205.  But it was the best nighttime lightning show of the summer in the far east metro area. There were dozens (if not hundreds) of lightning strikes from the Boring area up into the Southwest Washington foothills.  You can see a concentration of action from Cape Horn up to Yacolt and other points into the forest.  Luckily this whole area is covered by a cool marine layer right now, so hopefully no fires of signficance show up.

It was interesting to see the lightning flashing ABOVE the low clouds, at least that was the case when I looked out around 1:30am.

The storms have moved on, but we’re left with a thick marine layer; back to the morning cloud and afternoon sun routine.

Chief Meteorologist Mark Nelsen

10:30pm: Sudden Thunderstorm Development

August 18, 2012

Ugh…moments after I said “all clear for tonight” at 10:09, a solitary thunderstorm with about 8 strikes developed around Silver Falls State Park and has moved quickly north towards Colton.