A Pattern Change?

January 11, 2010

I found this on the HPC website today, it’s the extended forecast discussion (Thursday through next Monday).

“THE SPLIT-FLOW REGIME SEEN SINCE AT LEAST NOVEMBER WILL CONTINUE…THOUGH WITH AN INCREASINGLY ZONAL PACIFIC JET CUTTING THROUGH THE EASTERN PACIFIC AND AIMING TOWARDS CALIFORNIA…SYSTEMS MOVING THROUGH THE SOUTHERN STREAM SHOULD BE MORE POTENT. IN KEEPING WITH THE SPIRIT OF WHAT IS EVOLVING INTO A MORE TYPICAL FLOW PATTERN DURING EL NINO CLIMATE REGIMES…”

I was about to post about what I see on the maps for the next 7-10 days, but that sums it up well.  I would mildly disagree with the statement  that we’ve been in a split-flow regime since at least November.  It has come and gone, and really didn’t appear until after Thanksgiving anyway.  BUT, it has been a persistent feature of the maps for the last 5-6 weeks.  As for the big change next week, it seems to occur right after the weekend. 

Several thoughts on the long range maps.   1.  California is going to turn very stormy next week!  Lots of deep lows approach the northern California coast and tons of rain, mountain snow.

2.  A very strong Pacific jet will be aimed well south of us.  Check out the upper-level height anomaly for the 6-10 day period.  That’s unusually far south.  Once again…California is going to get nailed.  But this is not a great pattern for good Cascade snowfall here in Northern Oregon, or heavy rain here for that matter.  We get the leftovers and lows don’t move far enough north to give us decent south wind.

3.  Any shift farther north than what we see in the maps could put us in great windstorm territory, but I don’t see it for now.

4.  Cooler, but only up above…we’ve been in constant inversions here in the Portland Metro area, so daytime highs may not show it, but in general it looks like a cooler regime begins early next week.  Much better for the mountains regardless how much snowfall they actually get.

5.  I like it!   Other than the east wind excitement at Crown Point, we’ve gone two weeks without anything very fun weatherwise.  I could go for a change.

Today’s Crown Point Report:  Day #6 of the weather geeks enjoying the wind out there.  The Friday night freezing rain/shortwave dropped the PDX-DLS gradient down to around 7 mb Saturday morning, but then it ramped up again, reaching another peak last night around midnight, with Corbett reporting it’s second highest gust of the event, 61 mph, and an average wind speed above 40 mph for several reports…that’s rare.  Then the gradient backed off again this morning, dropping the wind way down.  I don’t think Tyler Mode recorded gusts above 80 mph today.  He’s recorded 90-100 mph gusts in previous years out there.  I stopped by around 1pm.  Saw Tyler, Runrain, Antipex, Kyle (from Clackamas), Yevgeniy and his friend.  The highlight was a couple that pulled up with a Christmas Tree.  She took a video of him screaming into the wind while he held onto the tree (pretty funny), then they tossed it over the edge as it flew towards Troutdale.  Some sort of ancient Druid custom apparently resurrected in east Multnomah County?  Not sure.  Of course I don’t approve of littering, but it’s a bare tree being thrown back into the government-owned woods.  Lots of trees fall in that area every year, so it’s a form of recycling I suppose.

Chief Meteorologist Mark Nelsen