More of the Same

July 25, 2007

SnapshotThe image to the left tells the story.  We are locked into a Rockies Ridge-Offshore Trough pattern   Long range (7-10 day) maps show no significant change.  Upper level heights lower slightly over the weekend, then rebound early next week.  The scorching hot July continues to our east.  I mentioned in the 11pm show that Missoula has recorded their hottest temp (107) and warmest low temperature (71) of all time this month.  On the other hand…Juneau has had over 6" of rain this month due to constant southwesterly flow around the trough.  That’s double the normal total and they’ve had rain just about every day this month.  I couldn’t handle a rainy/snowy winter and then a rainy summer on top of that.  I won’t be moving there anytime soon!  Another reason to enjoy the warm/dry weather here…Mark


Much Improved Weather

July 24, 2007

SnapshotAn editorial comment in the title of course.  I try to avoid that on-air.  Comments such as "a nice sunny day" during a drought aren’t very well received by viewers generally.  But I think most of us went outside this morning and noticed the cool/dry air.  It felt quite refreshing after a sweaty week around here.
I find it quite ironic tonight that after all the excitement (forecast) and hubbub about the "wet July weather", we’ll probably end up below average for the month!  In fact it’ll be our 7th consecutive dry month too.
This is assuming that our current and forecast pattern remains the same.  Long range models are in sharp agreement on the offshore trough-inland ridge pattern continuing.  It’s not all that much different from last week’s pattern, except that the low is a bit farther offshore this week.
A slightly closer trough over the weekend gives us stronger onshore flow.  But no threat for rain.  Enjoy the "boring" weather, and discuss it amongst yourselves…Mark


Back to Normal

July 23, 2007

SnapshotBusy fire season across the USA this year…running only slightly behind last year’s biggest ever! 
Big changes occuring this evening that threaten to bring "normal" Northwest summer weather back by midday tomorrow at the latest.  I’ll be right back…it’s 11:04pm and I have a weathercast…Now I’m back and it’s 11:12pm.
What’s left of the front sitting offshore all through the weekend finally moved through the area this afternoon.  It was followed by a good push of cooler marine air.  Of course that marine air has much lower dewpoints than the tropical airmass that was sitting over us for the last 3 days.  Twice this weekend I turned on the air conditioner (once in car and once in house), just because it felt too sweaty…not too warm.  So we’re all finised with that.  By the way the models nailed the drop in the dewpoint quite well.  They all showed a quick drop after 00z today (5pm).  Other than some leftover moisture in the morning, it appears that the developing Pacific High offshore will give us nice north and northwest wind all across the region the next few days.  That’s a great pattern for sunny/warmer weather inland with a minimum of low clouds.  The warmest days should be Wednesday and Thursday.
Interesting to note that the general pattern we’ve seen the last week or two will continue for the next week or so.  That would be a strong ridge just to our east and a trough offshore.  Models say the trough will edge closer again this weekend.  At this point it’s only deep enough and close enough for an increase in marine air.  I see no reason to put rain in the forecast.  But there’s no chance of a heatwave anytime in the next 7-10 days either.
A few interesting facts about this weekend that I noted.

1.  We only had .01" rainfall at PDX all weekend…oops.
2.  The baroclinic zone (frontal clouds/rain) were so close to Portland yesterday that it was a mostly cloudy day in Hillsboro but mostly sunny and much warmer out towards Troutdale.  Quite a variance for being so close to a front.
3.  Dewpoint topped out at 65 at PDX late this afternoon.
4.  Overnight low of 68 Sunday AM was NOT a record because we had that 74 last year on the 22nd! (same date).  What’s the chance?  But a very warm night eh?

That’s it…more tomorrow…Mark


Sloppy Weekend

July 20, 2007

SnapshotNot all that much rain today, but a dreary day for July.
Weather pattern is actually pretty straightforward tomorrow and Sunday.  One more system swings north off the coastline tomorrow night and Sunday.  Looks like almost all the precip will stay to the north and west of Salem tomorrow, and then drift a bit farther south Sunday.  The change in tonight’s forecast is that the ridge to the east shifts just far enough west to shove the weak front offshore Monday.  So I took the rain out of the forecast Monday.  With the ridge gradually moving a bit closer to us over the next 3 days, the airmass continues to warm.  By Sunday the freezing level is around 14,000!  Once the clouds break Monday, we should easily hit 80 or so due to that fact.
The forecast maps for next week still show weak troughing well offshore, but all models are quite a bit weaker with the trough than they were 24 hours ago.  Enjoy the drippiness this weekend…Mark


Earthquakes & Rainy Weather

July 19, 2007

JunkSnapshotSnapshot2

In the 10pm show tonight I’m talking about what might we see in the city of Portland with a great Cascadia Subduction Zone earthquake.  But did you realize that we know when the last huge earthquake occurred?  In the evening, January 26th, 1700.  Probably around a 9.0 magnitude quake just offshore.  How do geologists know?  If you have some time take a look at this info on the Orphan Tsunami of 1700 .  I think it’s fascinating reading, but of course I find almost anything scientific to be fascinating.  It’s a paper written by Brian Atwater  and others about the clues to a massive West Coast Earthquake.  And since I produced WAY too much content for a 2 minute story, here are two more graphics.  I could have spent a minute just on the Bonneville Landslide , pictured above.
Now, on to the weather…WET Need more info than that?  It was a nice break this afternoon and evening as showers quickly died down and the sun came out.  Most noticeable was the humidity, or more specifically the lack of high humidity this afternoon.  Dewpoints were way down in the lower 50′s this afternoon…all is back to normal in the Northwest.  That doesn’t include the bizarre late July rainy pattern of course.  A big slug of tropical moisture is approaching from the west this evening.  It’ll be here by daybreak and give us a very gray day tomorrow.  We actually have 2 of these systems on the way that include a significant low pressure center swinging northward along the coastline.  The first is tomorrow morning and the 2nd is Saturday night and Sunday morning.  Generally in the summer we have a large surface high pressure area offshore, so this IS unusual.  It messes up the windsurfers in the Gorge (no west wind), campers on the coast (too wet), and marine areas (no cold coastal upwelling without the northwest wind).
Because of these 2 systems, the weekend forecast does look off/on wet, but what about next week?  As I mentioned last night, I’m tired of pushing rain forward one day at a time.  So now that I see the 12z/18z GFS and to a lesser extent the 12z ECMWF show another upper-level trough nudging us the middle of next week, it looks safe to put a few showers in the forecast then.  Basically I don’t see anything in the next 7 days that shows the warm ridge to our east taking over again…Mark


Wet July?

July 18, 2007

SnapshotApparently that may be the case…maps are still looking wet.  Hopefully I laid out the  forecast problem pretty well  at the beginning of the 10pm newscast.  We appear to be trapped between the hot ridge to the east and a persistent trough offshore.  The trough does not come directly over the Northwest on any model’s map the next week or so.  But each model run and each model itself shows shortwaves brushing the Northwest.  Notice that the ridge is "always" pushing back towards us in the 5-8 day period.  At one point a few days ago we were going to have very warm ridging  for this weekend as the trough would back off to the west.  That’s not going to happen.  So I’m very suspicious about next week’s forecast too.  Except for the "green tomato" summers of 1983 & 1993, I can’t really find an instance of a week or more rainy weather in the latter half of July.  Get to work guys and do some research to find out if this has happened in the past.  I’m sure it has to do with the mothership hiding behind the moon though…Mark


Wednesday Soaking?

July 17, 2007

SnapshotNice little picture isn’t it?  It’s called a Haboob  and it’s a wall of dusty air sweeping across the Arizona Desert this afternoon.
That’s obviously not a problem for us the next 24 hours.  We’ve got a nice shortwave coming up from the south tonight, swinging around a large upper-level low offshore.  1.30" precipitable water combined with a 11,000′ freezing level sure seems to give us the possibility of significant rainfall.  I notice the rapid cooling of cloud tops to our south this evening coincides with significant radar echoes rapidly approaching from the south too.
Our model here (RPM), which is almost always too wet, shows a large chunk of Northwest Oregon receiving a solid inch of rain or more.  IF steady rain does develop as expected, with this warm of an airmass and good lifting that is not unreasonable.  As for thunderstorms…it’s going to be tough to get anything other than a flash or rumble with such solid cloud cover through the afternoon.
Thursday is definitely an "in-between" day with more sunbreaks.  Then another system offshore takes a swipe at us Friday, but this one is headed mainly for Washington.
Weekend models are in disagreement.  This is part of the big picture models are having trouble with.  Will the upper level low stay just offshore the next 7-10 days?  And how far offshore?  A slight movement farther to the west gives us 80 degree weather.  If it moves closer (like right now), we get rainy and cool weather.  Sure looks interesting, annoying to forecast for, and unusual for the latter half of July…Mark


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