Possible Hail or Thunder Later

March 15, 2011

We could see an active afternoon (assuming we get some sunbreaks later).  By “active” I mean a few spots of thunder or hail…some downpours too.  Check out the Storm Predictition Center’s discussion for the Pacific Northwest this morning:

WHILE MOISTURE WILL REMAIN MODEST /PW OF .50-.75 INCH/… SUFFICIENT INSTABILITY SHOULD DEVELOP TO SUPPORT A FEW EPISODES OF DEEP CONVECTION/STORMS.  DEEP…LARGELY UNIDIRECTIONAL WSW FLOW WITH 700-500 MB SPEEDS OF 50-65 KTS WILL SUPPORT ORGANIZATION OF THE ACTIVITY INTO BANDS…WITH EMBEDDED BOWING STRUCTURES/WEAK SUPERCELLS/LEWPS POSING A THREAT FOR LOCALLY DMGG WIND AND MARGINALLY SVR HAIL.  IN ADDITION…TOPOGRAPHICALLY-BACKED LOW-LVL FLOW IN CSTL VLYS MAY SUFFICIENTLY ENHANCE LOW-LVL DIRECTIONAL SHEAR TO YIELD A THREAT FOR A TORNADO OR TWO..ESPECIALLY IN WRN ORE/SW WA.  WHILE COLD ADVECTION WILL CONTINUE ALOFT…MOST STORMS SHOULD WEAKEN AFTER SUNSET.

Yuck…I hate reading all caps, but I’m sure not going to retype that!  I’d like to see a lot more clearing offshore; nothing is going to happen under this solid cloud cover through the early afternoon at least.

Chief Meteorologist Mark Nelsen


NOAA’S Tsunami Predictions

March 14, 2011

Has anyone noticed how good the Tsunami forecast times and heights were?  Especially the arrival timesI think I made an error.  NOAA changed the “forecast arrival times” in the verification so they could compare the model’s peak height with the actual peak height.  So I just deleted the first set of numbers.  It did seem a bit weird that the Tsunami arrived within one minute of forecast in all areas didn’t it? They say models were 3-15 minutes too fast.  Anyway, check these out:

LOCATION, Arrival Time,  Fcst Height/Actual Height (time is A.M., height is meters, some had no forecast or arrival times)

Neah Bay, WA: 7:10  .40/.43

Westport, WA: 7:25  .54/.46

Astoria:  7:44   .27/.18

Garibaldi:  7:18   

Newport: 7:26   .43 (actual)

Charleston: 7:15    .58/.71

Port Orford: (no arrival time)  1.82/2.02

Crescent City, CA: 2.50/2.47

Not detected:  Upstream on Columbia at Wauna or Skamokawa.

Now check out the gauge data from Garibaldi.  The wave arrives around 7:18am, but the largest fluctuations are more like three hours later.  I noticed down on the southern Oregon coast, where the wave was much higher, the highest amplitude was also in the 2-3 hour range (post-arrival).  Another good reason to keep in mind that often the succeding waves/surges are higher than the first.  You can also see that the northeast Pacific didn’t really calm down for about 24 hours.  Basically water was sloshing around all over the place on our side of the planet.

NOAA’s Pacific Marine Environmental Laboratory has an excellent animation of the surge spreading across the Pacific right here.

Chief Meteorologist Mark Nelsen


55 MPH Today!

March 13, 2011

It may have only lasted 10 minutes, but this afternoon’s cold front-squall line gave us the strongest wind gust in several years at PDX.
This is the first ever blog post “via phone” since I don’t gave power here at home…I think it’ll be quite awhile to get it back too since 50,000 PGE customers are suddenly out.  Oops…maybe should have picked up gas for the generator???
As you would expect…a very short-lived, but surprisingly strong event.

Mark Nelsen…


2:45 PM: Squalls Approaching

March 13, 2011

Looks wild the next 2 hours in the Willamette Valley!  By chance I was just checking in on the radar because I wanted to work outside, and see a full-blown cold frontal squall line moving into the Valley.   Note the obvious line in the middle of the radar imagery.  It runs from near Astoria all the way out of radar range to down around Eugene.

Three big effects coming with this: 

1. Strong southwest wind gusts 40-50 mph, and they’ll probably hit suddenly, like a spring storm.

2. Sudden temperature jump…we’ve had a chilly east wind all day but temps are in the 60s right around the cold front where the warmer air aloft has mixed down.  So today may end up being the warmest so far this year…if only for an hour or two.

3.  Brief, but very intense, rainfall.

This is a classic spring cold front…enjoy the dramatic weather and we’ll hope it doesn’t get TOO wild.

Chief Meteorologist Mark Nelsen


ONE Dry Day Ahead

March 10, 2011

A real windy afternoon today, peak gust at PDX was 41 mph at 12:16pm.  You have to admit models did really well showing the peak within a couple hours of 1pm too.  I know there was some serious “wishcasting” and “wishsatlooping” going on too the last 24 hours (like the new term?).  That then leads to disappointment by those hoping for a big surprise.  The PDX-OLM gradient ended up peaking at 11.5 millibars, which is quite close to what models had shown as well.

Real quiet tonight and Friday as we get a break between systems…then it’s on to a new round of frontal systems Sunday and on through the rest of the next week.  There is no sign of a nice break in the weather that we often see this time of year (at SOME point in March).  The Pacific Jet seems to want to end the season with a bang.  So enjoy the one dry day tomorrow…just maybe a morning sprinkle.  Brightest skies with sunbreaks should be after the noon hour.

Chief Meteorologist Mark Nelsen


A Classic Windy March Day Ahead

March 10, 2011

Gusty windy, sunshine, downpours, and temperatures not TOO chilly should really make it feel like March today.  Not one of those gloomy and rainy days, but an invigorating, refreshingly wet day. 

Did I “sell” that well?  I’m up early for my last school visit “field trip”.  I’m headed down the Valley to Trinity Lutheran Preschool in Mt. Angel and Aumsville Elementary (Toto!).  All that and back to Portland by 3pm.

Check out the nice curl of low pressure west of Astoria.  Looking at the IR loop you can see it has reached it’s maximum depth and is beginning to fill; good news since it’s a little farther south than expected.  The low is going to stretch a bit as it moves onshore.  In fact we are going to see the southern part of it drag across NW Oregon midday-early afternoon.  It’s called the “bent-back occlusion”.  THAT gives us a renewed surge of SW wind on the Coast and our strongest wind in the Valleys…sometime between Noon-2pm.  I like the term “poisonous tail of the bent-back occlusion”…sounds dangerous.  It’s an old saying in the Pacific Northwest referring to these situations.  We had one of those give us damaging wind back in November 2006 I think.  As that passes through, models show 13-15 mb. gradient from Olympia to Eugene, which gives a general guide of 40 mph gusts.  The icing on the cake this time of year is lots of mixing due to the warm sun inbetween showers.  The mixing allows stronger winds a few thousand feet overhead to show up at the surface, especially with heavy showers between the sunbreaks.  We will see some gusts in the 40-50 mph range.  Not a huge windstorm, but “Wind Advisory Worthy”, and enough for a tree or powerline to go down here or there.  Especially since we haven’t even seen a gust over 50 mph at PDX this winter!  It hasn’t been a big year for south wind at all (again).   By 5pm it’s all over and we finally get a dry day Friday!

Chief Meteorologist Mark Nelsen


East Wind Season Is Over

March 9, 2011

I’ve been putting together graphics for a winter recap AMS meeting and noticed this.   It probably confirms what a lot of you “east county” folks noticed:

We didn’t get nearly as much east wind this winter compared to the last two.  Most likely no complaining about that!  Last winter we had 77 days (November-February) with peak easterly gusts over 25 mph; this year only 40.  That’s a significant decrease.  Also, for a second winter we avoided any unusually high/damaging wind like we saw in January 2009.  The numbers here represent November through February.

The easterly Gorge wind disappears rapidly in March, and actually reverses to a dominate westerly wind by the time April rolls around.  The main reason is that “inversion season” ends; cold air doesn’t sit around long east of the Cascades in the lower elevations because of the increasing sun angle.  The Dalles, Pasco, Hermiston; all those folks see average high temperature rise above Portland’s by late month.  So far fewer periods of high pressure locked in eastside like we see in Winter.  The east wind is driven by that pressure differential across the Cascades.  In fact west wind becomes more common in the 2nd half of the month.  The 2nd (minor) cause of the wind reversal  is that we don’t get as many strong low pressure systems moving up against the West Coast, helping to pull that air through the Gorge.

Of course we will still get gusty east wind at times through the Spring, but for no longer than 12-24 hours at a time; either when a strong low approaches the coast, or more likely high pressure eastside along with it’s sunny/warm weather.  

 Chief Meteorologist Mark Nelsen