A Hot September Day

September 29, 2008

Snapshot  A scorcher today, by late September standards at least.  Vancouver, McMinnville, and Scappoose all made it to 92 degrees.  Areas exposed to the strongest of the east wind only made it into the mid 80s, so you can get too much of that warm easterly wind this time of year.  Too much mixing isn't always a good thing when you want to break a record.  We only tied the record of 89 degrees at PDX instead of hitting 90 for one last time this season.  BUT, it does feel good that the majority of us hit 90, there were a few doubters the middle of last week! 

One other thing was the warm overnight temps last night.  The easterly PDX-DLS gradient peaked out at 7 millibars this morning, keeping the wind blowing all last night in areas near the Gorge.  Troutdale had a low of 67 degrees overnight, and at 10pm the wind is still going strong, so I doubt it'll drop off before midnight.  If so, that's a record warm low for the day.  It'll also be the latest in Fall that TTD has stayed above 65 degrees.

I really screwed up the Coastal forecast today (that gives me 1-1 Chucky D!).  Easterly flow was still going at Newport at daybreak…temps had stayed around or above 70 most of the night, but a switch to SW wind around 7am meant the temp never climbed above 60 the rest of the day…too cool isn't it?  That cool southerly surge reached Astoria by midday, keeping temps there from getting much above 80 degrees.

This evening we've had some instability moving overhead, causing a freak out in the control room when the person driving the convertible suddenly had to go outside and raise it.  There were never any cloud to ground strikes and no precipitation was recorded at any official sites.  Looks like that was it for the next few hours, although another surge is in south-central Oregon right now.

Models are definitely converging on a rainy and windy period (real Fall weather) beginning Thursday and continuing through the early part of next week.  Of course each model run and each model itself has a different solution for surface low movement and cold front passage timing, so details are up in the air.  It's going to get quite wet for sure, hopefully enough to allow open burning again…I've got a big pile of brush, and last winter's Christmas tree, under a tarp ready to go.  Is that a bit trashy?  Not sure, but the needles are all gone…Mark Nelsen

A Warm Wind

September 28, 2008

Snapshot Things worked out about as expected today.  A nice strong easterly gradient through the Gorge peaked out around 5 millibars PDX-DLS this morning, but didn't drop much below 4 millibars even this afternoon.  That's a sure sign of Fall…an east wind that doesn't die down much in the afternoon.  In summer there's a very diurnal variation with it peaking out in the morning and dying down by evening due to the east side of the state baking in mid-summer sunshine.  

We just had our peak gust of the day (25 mph) here at the TV station on Highway 26 & Cornell at 9:03pm.  We are in the "West Hills Downslope Wind Exit Region"…or at least that's what I like to call it, or actually I just came up with that…pretty clever eh?  An increasing or at least steady wind at 9pm way over on this side of town makes me think that there are going to be a few spots that stay quite warm overnight.  Near the Gorge I think the wind keeps going…but PDX will probably go calm or just get some minor mixing off/on during the night.  With such a warm atmosphere developing overhead (+21degC 850mb by daybreak), temps holding in the mid 60s is possible even this late in the season.

The wind did make it to the beaches today, pushing just about all locations above 80 degrees.  I expect the same tomorrow, but then there is a shallow southerly surge that works up the Coastline tomorrow evening.  That puts them back in the 60's and lower 70s for Tuesday while we stay pretty warm inland.  I think Newport and a few other locations along the Coast will stay above 60 tonight too.

Models keep hinting at something moving up the Cascades tomorrow evening and Tuesday morning in the upper-atmosphere.  Normally one might think "What?  thunderstorms the last day of September?", but it's a very warm atmosphere and there were hundreds of lightning strikes over Nevada and Utah today.  We'll see what the next model run shows, but flow will be south or southeasterly, always good for thunderstorms.

We lose the offshore flow, but don't get any significant onshore flow, Tuesday and Wednesday.  There does appear to be a good push Thursday as a short wave swings through.  Then the "rain" door is opened up for the weekend.  Friday-Saturday look real wet…the GFS says we are going to get soaked.  Not sure about my dry forecast for Sunday…might adjust that after looking at 00z data.  The main point is to get your dry weather chores done by Wednesday, or Thursday at the latest.

I've turned the comments back on, but wasn't that a nice quiet Sunday on the blog?  After checking the stats I realized (and so should everyone else) that the number of folks reading this blog was WAY down over the last 4 days, as it always is during sunny weather.  The point is that very few people saw many of the postings, which is probably good.  About 1,300 page views for Friday and Saturday, as opposed to 8,000 on Monday August 18th…one of the heat wave days.  And by the way, there have been 96,000 comment posted over the last 2.5 years!  You people have been busy…Mark Nelsen

The Heat Is On (Late September Version)

September 27, 2008

Snapshot  We're all set for a dramatic warm up the next two days.  We hit 75 this afternoon at PDX, a nice change from the early morning fog and clouds. 

Strong easterly flow begins in the upper atmosphere (3,000'+) the next few hours, then surface easterly wind through the Gorge kicks in nicely by daybreak as well.  No low clouds here or at the Coast as a result.  Looking closely (with my old laser-treated eyes), it appears that the Gorge wind should spread out across the entire metro area by afternoon.  So I think this will be an event where northeast wind even blows out in Hillsboro and Forest Grove.  Peak gusts in the Gorge with a gradient up to 5 millibars or so should get to 45-50 mph.  Keep a close eye on that Corbett sensor tomorrow.

Easterly flow peaks tomorrow morning and then again Monday morning, then gets really weak and gradients go flat Tuesday afternoon.  This gives us 3 very warm days.  I see the 00z WRF-GFS has put the 92 degree surface temp isotherm over the Willamette Valley in spots again, so I'm sticking with the 90 degree forecast for Monday.  It still appears the easterly flow makes it to the Coastline tomorrow and probably Monday too.  But there is a bit of a southerly surge up the immediate beaches Tuesday afternoon, so much cooler then.

I've decided that with perfectly sunny weather it would be a great time to get outside the next couple of days.  That plus some excitement earlier this afternoon and evening in the comments prompted me to close the comments for at least 24 hours.  There's no reason to sit in front of a computer and get cranky with this beautiful weather.  Some would say that's an attempt at social engineering, but, well, it is.  We all know east wind will blow tomorrow and easterly gradients will pick up, nothing is going to change, you won't miss a thing!  Plus I still work tomorrow and Sunday, so I'll post again tomorrow afternoon…Mark Nelsen

A Dry September

September 26, 2008

Snapshot  It seems extremely unlikely that we'll have any more rainfall this month, so the final total should be less than .50".  It'll go down as another dry month in this dry 2008.  And it'll be the first real warm and dry September we've had for a few years.

Other than low clouds tomorrow morning, I think it should be a cloudless weekend.  One more band of clouds from the dying cold front offshore should move by mainly to our north the next 12 hours.  Surface high pressure develops to our north during the day tomorrow, keeping temperatures similar to today, or up 5 degrees at most…somewhere in that range.

Then a quick change occurs early Sunday.  Surface high pressure develops east of the Cascades.  This should be the strongest easterly flow we've seen so far this season.  00z WRF-GFS gives us a solid 5 millibars from PDX to the Columbia Basin.  Easterly flow is from the surface to around 2,500'.  That continues all the way through Monday evening.  In fact at 5pm Monday it still shows 3-4 millibars with a strong thermal trough in the Valley even then.  On Sunday afternoon the thermal trough makes it to the beaches, so that's why I pumped up the 80-88 degree forecast for the North Coast cities.  This evenings runs also make me feel a bit more confident about the 90 degree forecast for Monday.  I see the 92 degree isotherm shows up in the Willamette Valley on the 00z WRF-GFS for Monday afternoon, that's warmer than previous runs.  In fact both the 00z NAM & 00z GFS now show 850mb temps of +23 to +24 Monday afternoon.  That is VERY warm for the last few days of September…very rare indeed.

00z GFS pushes the rain off AGAIN!  It shows no rain until Friday…didn't it tell us about 3 days ago that it would rain sometime on Tuesday?  I've left the rain in for Thursday, since I hate to waffle around too much.  Plus I work both evenings this weekend, so PLENTY of time to update.

A personnel note:  You've probably noticed some moving around of the "talent" in the weather center.  That's what they call the on-air people in the TV world.  Of course some claim we have no talent at all…Anyway, I digress.  With the addition of the 4pm, 5pm, & 8pm weekday shows over the last 6 months, we are just about to finish adding a few new weather people:

1.  Drew Jackson has moved to weekday evenings with me.  He'll do the 8pm show on PDX-TV and 11pm KPTV show.  You'll see him off/on in the 4, 5, and 10pm shows too.  I will continue to forecast in the 4, 5, & 10pm shows.

2.  Rob Martin, an intern here 2 years ago, is now our morning meteorologist along with Andy Carson, mostly off-air for now.  He just got his Meteorology degree from the University of Utah.  He's a sharp guy who likes hanging around on the blog with you folks.

3.  Stephanie Ortmann joins us next week.  She has a degree in meteorology as well, from Florida State University.  Those of you in Eugene may recognize her or at least her name.  She is coming to us from Colorado Springs, but worked a couple years forecasting weather in Eugene recently.  Stephanie O. will do the weekday morning shows, and fill in other times as well.

The addition of these folks gives us the largest weather team (6) in Portland now, with lots of Northwest experience as well!

Mark Nelsen

Back to the Sunshine

September 25, 2008

Snapshot  I'm trying to stay ahead of the ball tonight (not really a reference to the OSU game, although I suppose it's timely).  The weather forecast is somewhat simple.  Last night's cold front has moved well off to the east, leaving us in weakening onshore flow.  When I showed up at work around 1pm, you could clearly see the surface low off of Vancouver Island.  That has now dissipated and moved inland.  Surface high pressure builds inland tonight, giving us weak offshore flow tomorrow.  That plus warmer air in the atmosphere overhead should give us about 10 degrees warming.

An upper-level trough passing by to the north Saturday keeps us from warming more than a degree or two.

All models are now in agreement with a strong upper-level ridge rapidly building directly overhead on Sunday.  This is partly due to deepening storms in the Eastern Pacific.  500mb heights go up to 586-588dm by Sunday evening.  That's a very warm atmosphere, especially for the last few days of September.  And it'll be centered directly overhead on Sunday and early Monday.  This time of the year it'll be easy to get easterly wind with this setup.  In fact Sunday and/or Monday we may see 80 degree temps at the Coast assuming the easterly flow makes it that far.  12z models had shown the thermal trough making it out to the beaches, and now I see the 00z NAM has easterly flow stronger near the surface than up at 850mb…that looks more like Fall than Summer.  It goes without saying that we're going to have one (last?) "heat wave" to wrap up this month.  That's why I put Monday's high up to 90 degrees.  850mb temps of +22 and easterly wind to PDX should do it.

The other piece of agreement in the models is in the long range.  They keep pushing the arrival of some wetter westerly flow farther into the future.  12z and 18z models all showed rain holding off until after midweek.  The combination of southerly upper level flow and/or easterly surface flow is going to keep us warm through the first day or so of October…Mark Nelsen

A Wet Evening For Some

September 24, 2008

Snapshot Quite a soaker for the east side of the metro area in the Cascade Foothills.  A band of rainfall has been lingering over the area for several hours.

Weak surface cold front appears to still be offshore, although it's awfully hard to find.

Post frontal day tomorrow looks really boring, then nicer weather Friday-Saturday.

Strong offshore flow and much warmer atmosphere prompted me to push forecast temps back up Sunday-Tuesday.  Models keep pushing back the westerly flow that punches into the Pacific Northwest next week.  The 00z GFS doesn't even have it until late Wednesday now.  The combination of a very warm atmosphere, southerly flow in the upper atmosphere, and offshore flow at the surface could get us surprisingly warm…September is going to end quite warm!  Mark Nelsen

Sunny Tuesday

September 23, 2008

Junk I ran across this while I was going through my afternoon forecast routine.  The 6-10 Day 500mb height outlook.  This should get a good discussion going.  I'll post later.  Okay, it's 10:24pm and I'm back.   What a nice day today…after the really chilly start.  I see Timber ODOT station hit 31 degrees early today, and HIO was 35.

Warmer temps tonight with the increasing cloud cover from the offshore cold front.  Some rain later tomorrow and then post-frontal showers are the story for Thursday.  Looks like dry Friday-Monday, but a front drags by just to the north Saturday.  That's why I put more cloud cover in and lowered temps over the weekend.  850mb temps peak out around +15 Sunday and Monday, although now I see the 00z GFS has a +19 deg Monday.  I trust the +15 ECMWF a bit more, it's been more consistent. 

Models have been hinting at a much stronger jet stream developing the middle of next week in the eastern Pacific.  The map above shows the 6-10 day deviation from normal 500mb. heights.  You can clearly see the big negative anomaly in the map.

The 00z GFS is a bit slower on development of westerly flow.  It has no rain Tuesday…so much for my wet Tuesday forecast…but there's always tomorrow…Mark Nelsen