Warm Rain and Hot Wind On the Way

May 12, 2008

SnapshotBack to work today after a so-so weekend weatherwise.  Forecast was pretty good, but a bit chilly again for early May.  Apparently we’ll make up for that later this week.  Several items of interest:

1.  Rain
Tropical moisture is streaming across the East Pacifc towards the West Coast tonight.  Models bring some of that inland tomorrow for a cloudy and sometimes rainy day in Northwest Oregon and Southwest Washington.  Not much to debate here.  It is strange to have rain forecast at the same time upper level heights near 580dm at 500mb.  The 00z GFS pushes rain north of us soon after daybreak Wednesday, with plenty of afternoon sunshine.  That plus a very warm atmosphere should push us into the low-mid 70s that day.

2. Hot Temps
No argument on the big heat up for Thursday-Saturday either.  Models have been very consistent for the last 24 hours.  Offshore flow begins on Thursday…in fact GFS has the thermal trough out along the beaches already in the morning.  Easterly flow + 850mb temps around +18degC equals a high right around 90 here in Portland.  So we’ll go from low-mid 70’s Wednesday to 90 Thursday…quite  a change.  Then I notice the last few runs of GFS and ECMWF (as of 12z) show no significant onshore push of marine air until Saturday night.  So…another day of even strong offshore flow Friday + 850mb temps of 20-22 degC should give us a high awfully close to 95.  On my chart, I see only 4 days in 9 years during the month of May have seen 850 mb temps above +20.  This will be a very rare hot spell indeed, especially if we do see 2-3 days at/above 90 degrees.  Just think, overnight temps in the city will be quite close to today’s high!  I almost planted some more summer veggies today, but figured it would be better to wait for much warmer soil Sunday or Monday AFTER the extreme and stressful heat has passed. 

3.  Dry May
We’ve seen very little rain this month and apparently very little is going to fall through the 20th based on current maps.  For those of you with freshly planted vegetation, you need to water the next few days…really soak those new shrubs because they’ll be fighting a dry, hot east wind Thursday and Friday.  These plants have gotten used to 55-65 degree days and some drips.

Mark Nelsen

A Short Post

May 9, 2008

SnapshotA short post tonight because I was too worked up preparing to watch the latest BSG episode…priorities once again.

Earlier this evening I was looking at the record highs for the next 7 days.  I notice that May 15, 2006 was 93 degrees.  Of course my short-term memory couldn’t quite remember that (even though it was only 2 years ago)…the May heatwaves are jumbled together in my head.  So luckily, this weather blog is archived!  Check out the right side of the screen and you’ll see every month since December 2005 is lined up.  Go to around May 11th 2006, and you’ll see that models had been forecasting 850mb temps around +16 or so, then ended up forecasting right around +20deg C.  We had 5 millibars easterly flow through the Gorge on that one day as well.  The maps for this next Thursday are almost exactly the same, so I figure there’s no reason not to put temps in the 90-95 degree range.

Okay, out of time…so have a good weekend…Mark Nelsen

Chilly, Then Hot

May 8, 2008

SnapshotI admit I’ve been a bit negligent lately.  I try to post something to this blog every day.  Lately the weather has been pretty slow too.

The constant onshore flow of marine air the last 2 days has really taken a toll on our high temps.  We’ve stayed in the mid-upper 50’s both days…only 56 today.  A slight upper-level ridge gives us warming throughout the atmosphere tomorrow and Saturday, which should help break up the marine layer.  As a result temps warm up to normal.  That’ll be nice.

Next weather maker is a cold front for late Saturday.  Quite a drop in the freezing level from around 10,000′ midday Saturday to under 4,000′ Sunday A.M.  Not a whole lot of moisture either with the front or behind it for Sunday.  Interesting how April and May have been chilly, but defiinitely on the dry side.  Looking at the 7-10 day maps, it sure looks to be mainly dry as well.

Speaking of 7-10 days:  Models are in some pretty good agreement on a strong ridge developing in the perfect location to give us unusually hot weather for mid May next Wednesday-Friday.  As you might expect, model solutions are varying day by day and run to run.  Some are way up in record territory for temps.  I see the 00z GFS again has 850mb temps up to beyond 20deg C and 592dm heights at 500mb.  The 00z GEM (Canadian) has gone nuts with a 596dm contour over southern Oregon next Friday.  If it was June, July, or August, that would give us 100 degree weather with offshore flow.  We’ve never been above 93 before May 22nd in Portland.  Twice in the last 7 years we’ve hit 95 in the 2nd half of May, both times 850mb temps at SLE were either 21 and 22 degrees at the peak of the heat.  This forecast ridge could produce those same temps.  One fly in the ointment is the 12z ECMWF.  It was significantly flatter with lower heights…we’ll see if it gets back on board at 00z or is a harbinger of flatter flow that the other models will follow.  Either way, get ready for a warmup!  Mark Nelsen

Birthday Special

May 6, 2008

SnapshotWell, I turned 39 today, which is only 1 year away from the big 40.  After I woke up this morning I looked in the mirror and thought "well, maybe I don’t look so bad for 40!, nothing special, but I’ve seen worse at this age".  That was before the shower and morning mocha.  The mocha, email, and weather maps always begin the day in my simple little life.   

Speaking of life, as I was driving to work I thought back over the last "almost 4 decades".  I don’t have anything to complain about.  Pretty good parents, great wife, good kids etc…  I never did anything really stupid, except for hitting 3 cars and skidding across an intersection in Seattle ON my 21st birthday.  Hard to believe, but that didn’t include alcohol…only moronic driving skills.

But enough reflecting on my life, how about that marine air!  A cooler day today…we dropped from 74 to 62 in one day.  Now cooler air moves in tonight and tomorrow in the upper atmosphere.  Our RPM model, including the one that shows the "sky" for tomorrow in our forecast grapic, insists there will be very little cloud cover tomorrow.  That models has done very well, so I put quite a bit more sun in the forecast.  I HAVE seen this happen when colder/drier air moving in up above disrupts and mixes out the moist marine layer, so I’m guessing this may be what happens on Wednesday.

Not much to talk about Thursday, Friday, or most of Saturday.  A cold upper trough arrives late Saturday and sticks around through Monday.  Unfortunately the rain threat seems to be centered on Mother’s Day.

Some of you have probably noticed, but the GFS and ECMWF has been insisting on some sort of strong ridging developing on the West Coast mid-late next week.  It’s still 7 days away, but they have quite high 500mb heights.  I see the 00z GFS says surface temps would be over 90 degrees with offshore flow!  Mark Nelsen

April Ends Chilly

May 1, 2008

SnapshotThis one surprised me…I added up the 60+ degree days during the February-April period the last 5 years.  Whew…it really has been chilly, but we’ve also had some mild springs lately.   Apparently this year is makeup time.  Makes me wonder if May will be cool again…that does seem to happen in La Nina springs.  However, April was a bit drier than normal, and most La Nina May months have been drier than normal as well.

Based on the forecast maps, I did start working in the garden again today, anticipating planting some "cool weather" plants/seeds next week.  It’s going to be warm enough for those now.  But even if you live in the city, I still would wait on the warm weather plants (tomatoes, corn, peppers etc…).  The ground is going to take awhile to warm up.  But it IS nice to see a sense of normalcy on the weather maps for next week.  In general the upper level heights and 850mb temps are warmer.  Not any significant, rain producing weather systems move through the Northwest either.  In fact the 00z GFS that just came out shows little to no rain in the next 7 days.  The 12z ECMWF was similar with high heights too.

The general trend may be warmer, but unfortunately a dying cold front will torment weather forecasters tomorrow and Saturday.  Some sort of light showers sit over us both days…Mark Nelsen