Warm Summer Nights & Improving Weekend Outlook

August 28, 2013

I’ve heard a few complaints this summer.  Not about the hot days (there haven’t been many), but the warm and humid nights.  A good reason for this…3 times we’ve seen a humid air mass overhead and/or light showers in the area for several days at a time.  It happened just before the 4th of July, a couple of weeks ago, and now it’s happening again this evening.  Dewpoints are way up in the 60s again.   Tonight and two weeks ago we have been in a pattern with moist flow coming up from the south on the back side of an offshore trough of low pressure.  It’s sitting just close enough to give us moisture, but not close enough to give us a big marine push with the cooler air.

Take a look at the 60 degree or warmer nights over the past 8 years:


We will end up quite close to June-August of 2009.  Of course that summer saw tons of hot days, but not much of the humid weather.  Brian Schmit put together this chart showing that this August will end up #2 for 60 degree nights here in Portland since 1981.


The urban heat island effect is more dramatic the last few decades due to the growth of the Portland Metro Area, but it seems to me we’ve had more of these “humid nights” the 2nd decade of my career compared to the first.  I can’t believe that this fall I will have been doing television here in Portland for 20 years!  Add on 2 years of non-television forecasting before that and I’m becoming an old man…22 years in meteorology.

Thursday could be a real interesting day.  Lots of tropical moisture, good lifting as the upper-low offshore kicks out, and some afternoon sunbreaks.  I think we’ll see thunderstorms around that could be real juicy.  00z WRF-GFS and our RPM are both showing that.  They are also showing some “training” of shower bands later tonight and early in the morning over our area.  That’s when a line of showers moves parallel to the upper-flow, allowing one shower after another to move over the same area.  With such a juicy atmosphere overhead, SOMEONE IS GOING TO GET SOAKED.  Not sure exactly where that will be.  We’ll know within 12 hours.

Beyond tomorrow, the big story is the 2nd upper-level low’s movement this weekend.  Once again models have slowed things down.  Plus now they are showing some offshore flow for Saturday = hot for the last day of August.  Labor Day Weekend is looking better and better!

Chief Meteorologist Mark Nelsen

Old Farmer’s Almanac Winter Forecast

August 27, 2013

(UPDATE: I was confused…this is the FARMERS ALMANAC, not the OLD FARMERS ALMANAC)  I like to post this once a year…for entertainment value only…


The forecast itself is utterly worthless; several studies have shown that.  I did my own on 3 winter forecasts from the late 1990s to 2000.  Temperature forecast for our area was about 50% correct and precipitation was 33%.  You’d be better off guessing.  Of course every once in awhile one of the forecasts will be correct, and someone will remember that for the rest of their life, telling me “it nailed the winter of 2009!!!”.

Here’s an interesting look at its accuracy from Jan Null of Golden Gate Weather Services:  http://ggweather.com/farmers/2007/index.htm

I really like how they claim to have some centuries old secret forecasting method…don’t you think they’d be rich by now and doing something other than publishing a paper almanac if that was the case?

Chief Meteorologist Mark Nelsen

ECMWF Monthly Maps

August 27, 2013

A day late, but here are the 4 weekly averaged 500mb height anomaly maps from the ECMWF ensembles:










The general theme of ridging beyond Labor Day continues, but this was the Sunday night run.  ECMWF runs since that time have backed off on the timing.  Take at look at the 12z ECMWF ensemble chart…in fact the coolest temps are just beyond Labor Day now:


There is some good news for Labor Day, the cold upper level trough appears to be arriving a bit later, so Saturday looks summery and Sunday could end up real warm/nice as well.  All is not lost yet!

Chief Meteorologist Mark Nelsen


Looks Like September (Weatherwise)

August 25, 2013

A busy day today at FOX12 since we not only put a fresh news studio on-air, but also switched the entire news operation to HD.  Hopefully I don’t look too old with the HD cameras.  As one professional told me “HD is great for video, sports, and wide shots, but is no friend to your face!”.

Anyway, we had some rain today!  .08″ at PDX brings the August total to….almost two tenths of an inch.  Don’t worry, there will be more.  We are clearly in a general weather pattern for the next 7-8 days that will produce below average temps and above normal rainfall.  The reason is an upper-level trough that lingers offshore through the week, then totally kicks inland over the Pacific Northwest during the Labor Day Weekend.  Here is the 500mb height anomaly from the 12z ECMWF for midweek.  Quite a deep low offshore for this time of  year:


Then see what happens next week, models all imply some sort of ridging over the Pacific Northwest…the 00z GFS anomaly map for next Tuesday (AFTER Labor Day!)


Now the 00z GEM (Canadian) shows the cool upper low over us all week, but, it IS the GEM, so I’ve ignored it.  For now…

The length and intensity of a  possible warm and dry spell after the 2nd of September is definitely up in the air.  Take a look at the 12z ECMWF ensemble chart:


a HUGE variety of solutions…from about average temps to a scorching early September heat wave.  Here’s the 00z GFS ensemble chart…


Same thing, although not quite a disparity between solutions.  The main message is cool for most of the next 7 days, then a bit warmer AFTER the Labor Day Weekend.

Chief Meteorologist Mark Nelsen


How do YOU rate Summer 2013?

August 16, 2013


We haven’t done a poll in a long time.  So here you go.  Let’s rate the summer so far.

Obviously we all have different criteria, including weather geeks who would like to see more thunderstorm action in the summer, so not exactly a scientific poll.

Warm & Humid

August 15, 2013

As promised, the humidity bumped up somewhat dramatically the past 24 hours.  Dewpoints went from the 40s yesterday to 60s today.  Dewpoint is the measure of the amount of moisture in the air.  Technically it’s the temperature at which fog would form if an airmass is cooled at a constant pressure.  As air cools it can hold less moisture, so at some point some has to condense out into fog droplets (or condensation on your cold drink).  Anyway, more moisture means your body can’t cool itself as well, thus the “sticky or sweaty” feel.


Last night we tied for the warmest temp of the summer at PDX (66), I see Vancouver was only 67 for a record and that tied the warmest of the summer too.  Our 66 was not since 3 record lows were 66-68 during a heat wave in mid August 2008.  Of course these numbers are dependent on the temperature not dropping lower before midnight since records are kept by calendar day.

We sure haven’t see the rain earlier anticipated though.  Starting with last night’s 00z models they turned much drier.  At least they caught the drier forecast 12 hours ahead of time, but I wish we could have seen that 1″ of rain in the Coast Range today.

Tomorrow should be warmer with less cloud cover and showers only developing over and east of the Cascades.  Weak and flat upper-level ridging develops over us Sunday through the middle of next week, then maybe troughing again beyond that.  Here are the two ensemble charts from the ECMWF and GFS.  First the 12z ECMWF, note the above average temps the first half of next week and then cooler towards the following weekend:


then the 12z GFS chart, closer to average through the whole run.  Note the operational is cooler than the ensembles for next weekend:


Here are the ECMWF weekly maps from last night’s run.  Interesting to note the strong ridging offshore in early September.  Otherwise no real negative or positive anomalies.





Last night I showed this graphic…


A sort of checkup on our summer weather so far.  For the record, Wayne Garcia gave it an A+ and Amy Troy an A-.  Or maybe the other way around.  Either way they are quite pleased with our summer so far.  The stats above are for PDX only.  Notice we had no chilly late spring/early summer weather.  Remember the run of 70s and even a few 80s in early May?  Then a big soaking of course.  So far we are above average on 80+ days, but do to the lack of extreme heat, we are only slightly above average with respect to temperatures.  As mentioned on an earlier post, we haven’t seen much heat, just 6 days at/above 90.  That’s normal for May-July.  And so far August appears that it COULD go down for below average 90 degree days.  We’ll see.  This doesn’t apply to all of Oregon.  I see that extreme SE Oregon saw its hottest July ever!


Chief Meteorologist Mark Nelsen

A Taste of Fall In the Weather Maps

August 13, 2013

After a week on vacation, I came back to weather maps that look a little more “Fall-ish”.  It’s hard to describe, but the upper-level maps (mainly 500mb) have a little more action moving around the northern hemisphere compared to a week or so ago.  We also have a wet weather system sitting just offshore that promises to give us some humid and cooler weather the 2nd half of this week.


This plus no sign of real hot weather means that we’re going to make it through a good chunk (or all) of August with no heat wave!  This has been a summer of very little hot weather  west of the Cascades.  We’ve seen only one day 95+ here in Portland so far this summer.  Last year we had 6 by mid-August.  Salem has seen 3 and Eugene 6 so far this year…clearly a nice marine influence on the high temps here in the metro area.  Yet even with the lack of extreme heat we have seen a lot of sunshine and very warm temps interspersed with brief cooldowns.  I think most would say this summer has been great.  We haven’t had a below normal month temp-wise since January.  So a decent spring followed by a nice summer, what else can you ask for?  Okay, maybe a chance to actually see a thunderstorm in the city of Portland?  We haven’t officially seen a thunderstorm at PDX since last September.  But at least the chilly summers of 2008, 2010, & 2011 are a memory (for now).

What’s on tap?  The juicy system offshore drags its sorry tail end through the Pacific Northwest Thursday and Friday.  Lots of clouds, humid weather, and showers may be popping up both days.  Possibly convection (thunder) either day.

Beyond that we should see some sort of ridging, although once again it appears it won’t be a setup for hot weather.  Still, quite a bit of disagreement on strength of ridging next week…notice the 850mb ensemble chart from the 12z ECMWF today:


notice the average is higher than the operational run, a clue that the ridge may be a little stronger than what we see on the maps.  The 12z GFS:


Similar look with the operational a little cooler than the average.

So…summer continues with no real extremes over the next 7 days or so.  Enjoy.

My bike ride last week went better than expected.  I survived and had no major issues.  For ME, it was a good accomplishment.  That road from Enterprise to Asotin, WA is amazing!  Check it out on Google Maps.  A 10 mile drop with curves down 3,000′ to the Grande Ronde River and then a rise 3,000′ in 10 miles via switchbacks up the other side is incredible…from sagebrush to forest in just an hour and a half or so.  That was my favorite day.  The next day was the hardest though, from Asotin, WA to Dayton, WA.  A long hot climb at the end of the day.  My hind end is just now recovering and I won’t be touching that bike for awhile!

Chief Meteorologist Mark Nelsen