Another Busy Evening

March 31, 2006

Morning sunshine really helped to destabilize things this afternoon as the conveyor belt of moisture from the south continued.  So showers and thunderstorms popped up.  Most intense was a complex of showers that developed east of Silverton, move up through Estacada, Sandy, and NE towards Cascade Locks & Hood River.  A 2nd "blob" of showers consolidated nicely this evening and really soaked the Columbia River corridor from Portland to Longview.

We should avoid heavy downpours and thunder tomorrow since this most recent upper-level low will be moving off to the east.  But it’s Spring and another one is nipping at it’s heels.  Models say the cold front should actually hold together and arrive with solid rain Sunday morning.  Either way a wet weekend.  Not good for yard work or rain-free outdoor activities.

By the way, I showed a graphic of Hawaii rainfall this evening and perpetuated one Hawaiian Urban "Rainfall" Legend.  Mt. Waialeale is not actually the wettest place on earth.  It’s in India, but they are quite close…about 460" per year.  Go to this great article from the Honolulu Star-Bulletin for the details…interesting article.

And if you’re interested in more about Hawaii’s incredible 6 weeks of rain, check this out:

Stay dry this weekend!  Mark

More Cold Showers

March 30, 2006

Radar scope (actually there is no scope, but it sounds like I’m on a submarine if I say that) really lit up around 5:00pm today.  Nice line of thunderstorms moved through McMinnville-Newberg corridor, producing 5-8 cloud-ground lightning strikes and heavy rain.  But the strongest cell I’ve seen since last summer developed soon after just west of Forest Grove then moved north across Highways 6 & 26 near Timber.  Lots of strikes and probably hail with that one.  But then it was all over by 6:30pm.

Unstable southerly flow continues tomorrow, and our model here (a WRF model) shows more breaks in the cloud cover for better heating.  That may give us more widespread thunderstorm activity.  Lifted Index is still a nice zero or slightly under.  CAPE on the 00z MM5 from UW is not too impressive, so I doubt it’ll get too wild, but it’s a nice pattern for afternoon spring storms.

By the way, when we do have good storms in the region and a weathercaster is "in the house" (in the weathercenter), keep watching this link:

we call it the KPTV FLOATER image, it’s just a snapshot of our radar screen.  Of course other times it’ll show absolutely nothing, but always check it out if you know we are here watching storms develop.

An Old Friend Returns

March 29, 2006

All is well with the world this evening.  A solar eclipse and then…the Portland WSR-88D radar is back in operation.  I don’t like having spring showers & thunderstorms with my 11 year old friend not working.  Good job National Weather Service getting that back up and working ahead of schedule today!

Looks like next upper-trough approaching quickly tonight, taking the "dive-south" route towards California.  Showers likely tomorrow, then Friday should be quite a bit more convective as Lifted Index goes to zero or slightly below.

Then a 2nd trough dives in for Monday-Wednesday.  Bottom line is active weather some days, slow and gray others, and no stretch of warm 65 degree or warmer weather.  We have been spoiled the last 3 years with 2-6 days of 70 degree temps in March.  We had none this year.

I have Sunday dry in the 7 Day forecast, but GFS does NOT agree.  May need to put showers back in on Thursday night’s broadcast.

First Thunder Day

March 28, 2006

As I mentioned on the 10 & 11pm broadcasts tonight, March 28th will definitely go down as the first widespread "thunderstorm" day in the spring here in the Northwest.  We recorded over 200 strikes across Oregon.  They were spread all across the state from the Coast to the Idaho border.  Scattered storms developed and moved north, away from a California system supplying the moisture.

Tomorrow the flow overhead turns onshore, which should give us lighter afternoon showers.  Onshore flow also means a bit more cloud cover and cooler temperatures.

Long range maps show this active pattern will continue with deep troughs dropping in towards California, which gives us southerly flow and moisture, then cooler air as they move on through.  Those of you looking for 70 degree weather will have to wait into the first week of April at least….Mark

Thunderstorms Developing…2pm

March 28, 2006

Looks like temps warmed plenty for convection to pop up in the "perfect pattern" for thunderstorms (see last night’s blog).  Several lightning strikes already at 2pm near Mill City and Sweet Home.  Unfortunately, the PDX-RTX radar is out of comission for at least 2 more days!  These showers will move either due north or slightly north-northwest, which puts them over the metro area by commute time.  Could get interesting for a few hours…Here is a link to "another" radar in this time of weather geek desperation.  Of course it’s not nearly as powerful as the other WSR-88D radars, but it’s better than nothing right?  Mark

The Almost Perfect Setup

March 27, 2006

Funny how just after I blogged about thunderstorms last Friday, tonight we have the perfect weather pattern for thunderstorms westside.  The only problem is that we probably aren’t warm enough.   Take a look at the map below.   It is the MM5 model from the University of Washington.  It shows the height contours at the 300 mb level (about 34,000′).  Notice the big upper-low off the N. California coast, and the flow around it coming not from the south, but slightly from the southeast.  That’s VERY good for thunderstorms west of the Cascades in the warm season.  As a wave rotates around the low, it encounters air that is "splitting" or diverging "apart" over Western Oregon.  Notice how some of the flow heads back towards the low and another part is headed up towards Washington.  That produces upward motion and can sometimes set off thunderstorms even in the middle of the night.  And with offshore flow at the surface due to the low offshore, we get warm weather down here at sea level too.  I have noticed that just about every single "thunderstorm night" we’ve had here in Portland in my career (since 1991), has been in this pattern.  Southeasterly flow with waves rotating up from the south or  southeast.  So hope for this pattern as we head towards summer!Snapshot_1  Oh, and I can’t figure out how to wrap the text around this image and it’s 11:20pm, so that’s the way it goes…Mark

Spring Storms

March 24, 2006

There were just a few scattered lightning strikes today, mainly offshore, but we are entering the season now where it’s quite a bit easier to hear a rumble of thunder west of the Cascades. The reason is that the land is beginning to warm up, yet we still have chilly air overhead to give us unstable conditions (depending on the weather pattern at the time of course).  Lightning2_3 Click on the image to see it full-sized.

This brings up a question a viewer emailed me today.  George from Tigard asks where he can find a link to live lightning information.  Here’s the deal.  There is national lightning detection network (the U.S. NLDN®) that  constantly detects lightning discharges to ground. Each lightning event, called a flash, is recorded at the NLDN Network Control Center at Vaisala’s Tucson Operations. Each plus sign on the map represents one recorded flash.  Since one company runs all the sensors, you have to pay for the data.  Because of that we can not redistribute the information (oops, hopefully the lightning police won’t be showing up at my door tomorrow!).

So there isn’t any "live" lightning strike information on the internet.  You have to pay for it, and it isn’t cheap.  Go here if you are interested:

In the future lightning could be detectable from space (NOAA is working on it now).  If so, that means cloud-cloud strikes would be detected too.  Most likely that would be free information if the government is the one collecting the data at that point.

Enjoy the weekend, it’ll be a bit chilly, but some dryness hopefully early Saturday and late Sunday…Mark