Back At Work

August 23, 2010

I’ve exhausted the vacation accrual account, so it’s back to work now.  Other than a day or two here and there, I won’t be taking a bunch of days off until Christmas week.  My hunch is that the weather should be much more exciting then (La Nina…La Nina…La Nina…).

For the short term, my internal debate of the night is whether to raise the 90 degree forecast high.  I figure at least 10 degrees warming tomorrow, but less than 15.  That gives us somewhere between 90-95 degrees.  The easterly flow looks to be a bit stronger than what we had during the heat wave a week ago.  WRF-GFS shows 4-5 millibars easterly gradient through the Gorge.  That should give us some gusts 30-40 mph in the usual windy spots at the west end of the Gorge, maybe 25-30 mph eastern suburbs.  The wind is pretty much gone by daybreak Wednesday though; this is going to be a quick offshore flow event.  In fact it’s all westerly at the surface by later Wednesday afternoon.

A strong marine push Wednesday night plus major cooling in the upper atmosphere should combine to give us one of those “double-whammy” summertime cooling days.  Down 15-20 degrees in one day.    I notice the 850mb temps drop from +19 Wednesday afternoon to +6 Wednesday PM.  Then down to +4 or so Friday?  Whew…that’s September for sure.  Our August chart for 850mb temps shows only 5 days out of the last 310 (10 years) with temps at/below +5. 

So basically the Fall-like weather that started late last Wednesday will contine through the foreseeable future, interrupted only by these 3 warm days!  Is it time to kiss goodbye to my little “grape-size” cantaloupes growing on the south side of my house???  I think so…there’s no way they are going to make it with lots of 60-70 degree days in the future.

Chief Meteorologist Mark Nelsen

Feels Like Fall!

August 20, 2010

It sure looks chilly the next few days…and today was the “warm up” to the Fall-Like weather.  Lots of 40’s in the metro area and I see even a few upper 30s.  It appears even Hillsboro may have hit the upper 30s briefly…we’ll know after 11am.   The weather maps look more like early Fall too…cool to very warm to cool again in just a 7 day period.  Something for everyone and the threat of consecutive days of summer heat are over.

Just in case you have a LOT of time and want to know what I’ve spent my days off doing the last few weeks, here’s a link to the Chicken Coop page.  I’m almost ready to go back to work and sit in a chair again.  I’ll be back Monday.

Chief Meteorologist Mark Nelsen

An active afternoon?

August 17, 2010

An attractive picture off the southern Oregon coast this morning. Thunderstorms started popping up around 7 a.m. This is associated with that upper-level low that looks to be pushing eastward. Models have it tracking up over the central Cascades and could impact the central Valley this afternoon. My forecast for today calls for some some thunderstorms late this afternoon and evening in parts of central and eastern Oregon. There are some pretty good CAPE values for this afternoon near Eugene and Salem. I am not anticipating any action there but with that high CAPE, that would be the best spot in the valley where some storms could pop up.

Meanwhile we remain under a heat advisory for the northern and central Willamette valley. One more day of 90+ degree weather before the cool down begins. Who’s ready for it?

Pat Rosborough

Dust From Mt. St. Helens

August 14, 2010

Check out the early morning visible image…either smoke from a fire or blowing dust (more likely) is streaming off of the area around Mt. St. Helens.  Actually the more I look at the loop, it sure looks like a few just a few miles west of the crater.  Dust doesn’t blow 40 miles away…although maybe this morning it is? 

11:45am Update:  Sure enough…driving to Seattle right now and just passed under the dust cloud.  Definitely not smoke.  I see Timberline 7000′ wind has averaged close to 40 mph…plenty windy to stir up the dust.

Heating up much more quickly today…but that strong east wind will keep the max temps from getting too crazy.  I still like the 95 forecast for today.

Chief Meteorologist Mark Nelsen

3-4 More Hot Days

August 13, 2010

Here is a cross-section from the WRF-GFS model (UW).  You have to read it backwards (after you click on it for a better view).  That means time goes from right to left.  5pm today to 5pm Monday.  Those are wind barbs in knots.  Notice the deep layer of easterly flow all the way through Monday afternoon.  It’s not insanely strong, in fact it’s a bit weaker after tomorrow, but it’s there nonetheless through the next 3 days.  This spells at least 3 more very hot days (95-100).  Those spots on hills near the Gorge have very warm nights ahead…in the 70s.  It’s unlikely that lower elevations (most of the populated areas) will stay warm…this time of year the longer nights allow temps to fall off more in the valleys.  Will we hit 100?  Maybe, or maybe not…it’ll be close.

Models are in agreement on a major change Wednesday and beyond…much cooler, back to our usual normal to cooler than normal temps with lots of lingering morning clouds.  This hot spell is just be a short detour around a slow moving Winnebago while winding down the mild summer road called 2010.  Nice poetry eh?

Now the transition between the heat and the big onshore push could be interesting.  Models have been waffling around with an upper-level low that may drift through the Pacific Northwest on Tuesday.  The 00z GFS is especially encouraging and appears to forecast a thunderstorm outbreak across our area during the evening and overnight Tuesday night.  I doubt the next model run will look exactly the same, but hopefully we get SOMETHING before the end of summer.  This has been one dead summer for thunder west of the Cascades…not too unusual but we can hope at least.

I’ll be off on one LAST week of vacation next week, back on Monday the 23rd.  If we get some exciting weather Tuesday evening I’m sure I will be on here though.

Chief Meteorologist Mark Nelsen

July Heat

August 13, 2010

Yes, I know we’ve started a heat wave and it’s mid-August, but I see NCDC just released their global wrap-up for temps.  For land-ocean combined it was the 2nd warmest July (globally) on record.  I really like the image that goes with it.  See the mega-heat in Eastern Europe and hot conditions in Africa plus Eastern North America.  Can you tell where the persistent troughs were in the northern hemisphere?  Right over us and just east of all that heat in Europe; maybe right over Siberia.  In the southern hemisphere (winter of course), notice the cold conditions in South America, but very warm in most of Australia and Africa.  As always, you can click on the image for a FAR better view.

Forecast Ensembles For Discussion

August 12, 2010

It’s time for some meteorological fun…let’s talk ensembles…good times.  You DEFINITELY need to click on the image to see what it is, and even then it’s a bit hard to read, but good stuff for the weather techie.  The top three images are the 12z GFS, ECMWF, and CANADIAN (GEM) models for 12z Tuesday…or 5am Tuesday morning.  These models ran this morning.  Those are 500mb heights (around 18,000′).  Notice the dramatic difference between models.  The ECMWF rams an upper-level low right into our region Monday night and Tuesday, putting a quick end to the heat wave.  The GEM is similar to the GFS, keeping it hot through at least Tuesday.  But there’s a bit more to the story.  Look at the “ENSEMBLES” from each model.  As mentioned in a previous post here, ensembles are multiple versions of the same model run…they often give us an idea if the “real operational” run of a model is an outlier. 

Looking at those ensembles something interesting shows up.  The operational runs of both the GFS and ECMWF (especially this one) both move the upper-low much closer and have it deeper than the “mean” of the ensembles.  It really sticks out for the ECMWF.  That casts some doubt on whether there will be a big cool-down Tuesday and Wednesday as it shows.  Due to this we’ve stuck with the 100 degree temp on Monday and put in a slower cool down Tuesday-Thursday of next week than what the ECMWF or some other runs of the GFS show.  We’re really trying to avoid model-riding, but that pony just keeps beckoning…can’t have much more fun than this with a mostly sunny 7 Day forecast!

Obviously the details of the 2nd half of our heat wave have very low confidence right now.  Those upper-level lows are a real pain! 

We DO know that hot weather is still on the way, and we probably won’t break any records.  The record highs at PDX for Saturday through Tuesday are 102, 100, 102, 105.  Those are from a heat wave in 2008 and another hot spell in 1977.  I think Monday (102) could be close.

Chief Meteorologist Mark Nelsen