Arctic Air Next Week?

Wednesday, November 30, 2011
1:01 P.M.

Yeah, I know No-Shave November is completely unrelated to weather. However, the model runs this morning made me hesitant about shaving my patchy, warming layer of facial hair. Remember how I was talking about how areas east of us would see very cold air next week due to the huge high pressure over our area creating a trough in the jet stream east of us where arctic air can invade? The big dome of high pressure is now forecast to move a little bit to the west next week or so.

If this holds true, we will see frigid temperatures, and if we have moisture, we will certainly see snowfall in the lowlands.

Take a look at the model from last night. I showed this picture in my previous blog post. The high is too far east for the Pacific Northwest to get cold air, but Montana would get frigid temperatures if this were to happen.

Valid 04:00 am PST Wed, 07 Dec 2011 - 180hr Fcst - UW 00z 36km WRF-GFS 1000-500mb thickness, SLP (last night's run)

This morning's run, just 12 hours later, is completely different. The high is further west, and Washington would be colder than a toilet seat in Siberia. Ok, maybe it won't be that cold, but high temperatures would be well below freezing, and low temperatures would be in the teens in Seattle with single digits in the suburbs.

 Valid 04:00 pm PST Wed, 07 Dec 2011 - 180hr Fcst - UW 12z 36km WRF-GFS 1000-500mb thickness, SLP

Look at that! Much colder air over our region, and the high is only slightly further west. This just shows the thickness of the atmosphere, where lower thicknesses generally equal colder temperatures since cold air is denser. Let's take a look at the surface temperature predicted at this time.

Valid 04:00 pm PST Wed, 07 Dec 2011 - 180hr Fcst - UW 12z 36km WRF-GFS 10m winds, 2m temp. SLP

In this picture, it is very cold over our region. There would also be strong winds through the Fraser River Valley as the cold arctic air spills into our region.

Valid 04:00 pm PST Wed, 07 Dec 2011 - 180hr Fcst - UW 12z 12km WRF-GFS 10m winds, SLP

Will this change? Absolutely. The models are not very accurate this far out. In fact, it could all change in tonight's run. However, it is interesting to see. Hopefully, it won't change. Models don't give us any moisture while we are this cold, but if moisture ever comes in, it will be in the form of snow for everyone.

Bottom line: don't get too excited yet, but there is hope for some interesting weather. 

Thanks for reading, and do some cold dances for me! Hopefully, you'll be doing snow dances next week. :)

Charlie

High Pressure, Inversions, and Fog

Tuesday, November 29, 2011
10:59 P.M.

Photo Credit: Kevin Ebi @ Living Wilderness

The next week or beyond will be very boring and uneventful for meteorologists. The culprit? A HUGE ridge of high pressure off the Eastern Pacific.

Take a look at the current atmospheric configuration from tonight's 00z UW WRF-GFS run.

Valid 10:00 pm PST Tue, 29 Nov 2011 - 6hr Fcst - UW 00z 36km WRF-GFS 1000-500mb thickness, SLP

There is a very, very strong ridge of high pressure over the Eastern Pacific. We have a weak system pushing through right now, but after that system passes through, we will be very dry, as this ridge will push the jet stream up north into Alaska, preventing any storms from reaching our area. Additionally, with light gradients over our area, cool, dense air will sink down to the surface and create an inversion, which is where the air at the surface is colder than the air aloft.

Inversions are very stable, and do not mix up the atmosphere much. Due to this lack of mixing, we often get fog and smog, as pollution gets trapped in the inversion over our area. People with asthma should be careful in the coming week, as they may encounter respiratory problems. People may also need to limit exercise or strenuous activity outside, as the air may irritate the lungs and make it hard to breathe.

This ridge ain't going anywhere. The extended WRF-GFS model at the UW goes out to 180 hours, and the ridge is still there and is stronger than ever.

Valid 10:00 pm PST Tue, 29 Nov 2011 - 6hr Fcst - UW 00z 36km WRF-GFS 1000-500mb thickness, SLP

While we are relatively warm aloft and cool at the surface, areas east of us will see numerous arctic outbreaks due to a huge trough in the jet stream. If this high was further west, we could be talking about some arctic air for our region. Alas, it is too far east. The plains should be very cold at times this coming week.

If you want to escape the haze, fog, and smog associated with this inversion, head into the mountains! The air will be warmer and cleaner. You'll look down at the Puget Sound lowlands and think "Was I really breathing that?" Inversions are gross... they indicate lame weather for us meteorology nuts while suffocating us all in dirty air. These inversions used to kill... the London smogs are a great example. Since then, people have burned cleaner materials (ex: natural gas as opposed to wood-burning stoves) and inversions now are much "cleaner" than they used to be in most places. Nevertheless, I'm not a fan.

Thanks for reading!

Charlie 

What a Convergence Zone!

Monday, November 28, 2011
4:22 P.M.

05:31 pm PST Sun 27 Nov 2011

Sorry for the lack of posts over the Thanksgiving weekend, I was at home and the internet there is dreadfully slow... so slow that it is impractical to use. And forget about using blogger...

Last night, we saw an incredibly well-defined convergence zone sweep through the region. Cliff Mass talked about this in the weather class I have with him, and he mentioned that one place north of Seattle recorded an inch of rain in an hour. That's an incredible amount of rain. The last time I witnessed something like that was on December 14, 2006, when a very strong squall dumped an inch of rain in an hour over Seattle.

The video below shows the rainfall in Seattle that night. As you can see, rainfall rates of an inch per hour are incredibly heavy, and are rare in the Seattle area.

You don't want to be biking through that!

This convergence zone could have been thought of as a "grand finale" for active weather in the Seattle area. November is coming to a close, and the last week of November, which is climatologically the stormiest time of the year for our area, is nearly past us. The next 10 days will be incredibly boring, as a HUGE ridge of high pressure parks just off our coast and stays there.

The ridge is already building right now, but after a weak system rolls through on Tuesday, this ridge will be in full-force.

Look at the size of this ridge by Wednesday afternoon.

Valid 07:00 pm PST Wed, 30 Nov 2011 - 63hr Fcst - UW 12z 36km WRF-GFS 1000-500mb thickness, SLP

This model shows the "thickness" of the atmosphere between the 1000 and 500 millibar levels in decameters. The thickness can be thought of as the difference in height between the two levels. This big ridge of high pressure warms the air aloft, making it less dense. Since the air is less dense, there is a greater distance between the 1000 and 500mb levels of the atmosphere, and hence, a greater 1000-500mb thickness. At the surface, the ridge is expected to be around 1040 millibars, which is disturbingly high pressure. I say "disturbingly" because pressure that high generally means that this ridge ain't going anywhere for awhile. Unfortunately for weather nuts like me, that looks to be the case.

Valid 01:00 pm PST Sun, 04 Dec 2011 - 153hr Fcst - UW 12z 36km WRF-GFS 1000-500mb thickness, SLP

Later this week, the ridge will grow even larger, pushing the jet stream up to the arctic circle. This spells atrociously boring weather for our region. Get ready for inversions, deteriorating air quality, and pretty bad sailing

Stay dry out there! It shouldn't be too hard...

Charlie

Statistics From The Past Storm and Thanksgiving Travel Woes

Thursday, November 24, 2011

1:16 P.M.

November 23, 2011 - taken from KOMO News

I finally found some stats from the storm that hit us earlier this week. Below are some rainfall totals for areas in Washington from 7 A.M. Monday to 7 A.M. Wednesday. These statistics were taken off Scott Sistek's KOMO blog, "Partly to Mostly Bloggin'." It is a very good article about this storm, check it out here.

• Anacortes: 1.05"
• Auburn: 2.50"
• Bainbridge Isl: 5.11
• Bellevue: 2.32
• Bellingham: 1.79"
• Bothell: 3.00"
• Bremerton: 4.92"
• Burlington: 1.57"
• Carnation: 2.13"
• Concrete: 3.62"
• Edmonds: 3.65"
• Everett: 3.25"
• Federal Way: 2.66"
• Ferndale: 1.88"
• Forks: 3.02"
• Friday Harbor: 2.10"
• Gig Harbor: 3.94"
• Issaquah: 2.37"
• Kent: 2.54"
• Kingston: 4.56"
• Kirkland: 2.85"
• Lake Stevens: 2.88"
• Lynnwood: 2.63"
• Maple Valley: 2.10"
• Marysville: 3.35"
• Mercer Island: 2.89"
• Montesano: 4.03"
• Mount Vernon: 1.79"
• North Bend: 2.88"
• Ocean Shores: 4.04"
• Olympia: 5.07"
• Pakrland: 2.89"
• Port Angeles: 3.89"
• Port Orchard: 3.04"
• Port Townsend: 1.32"
• Poulsbo: 4.95"
• Puyallup: 2.58"
• Redmond: 2.42"
• Renton: 2.09"
• Sammamish: 2.33"
• Seattle: 2.98"
• Sequim: 3.75"
• Shelton: 5.32"
• Stanwood: 2.34"
• Tacoma: 3.08"
• Woodinville: 2.54"

I did some additional research, and found some additional rainfall statistics from the NWS office in Portland. These amounts were taken from 6 A.M. Monday to 8 P.M. Wednesday. It looks like the heaviest rain was concentrated in the Mt. St. Helens area, with June Lake getting 10.50 inches!!!

JUNE LAKE,WA...............10.50  ...THROUGH 8 PM...  
 SHEEP CANYON, WA...........9.70   ...THROUGH 8 PM...      
 CEDAR, OR..................9.00   ...THROUGH 8 PM...
 FRANCES, WA................8.70   ...THROUGH 8 PM...
 FOSS, OR...................8.36   ...THROUGH 8 PM...
 SPENCER MEADOWS, WA........8.00   ...THROUGH 8 PM...
 LONE PINE, WA..............7.90   ...THROUGH 8 PM...
 SOUTH FORK RAWS, OR........7.79   ...THROUGH 8 PM...
 LEES CAMP, OR..............7.60   ...THROUGH 8 PM...
 COUGAR, WA.................7.52   ...THROUGH 8 PM...
 SPIRIT LAKE, WA............7.00   ...THROUGH 8 PM...
 SURPRISE LAKE, WA..........6.40   ...THROUGH 8 PM...

This storm also packed a lot of wind, especially down in Oregon. I also got these statistics from the NWS office in Portland.

PEAK WIND GUSTS FOR TWO TIME PERIODS...
    FIRST ROUND TUESDAY THROUGH 815 PM
    SECOND ROUND BETWEEN 815 PM TUESDAY AND 615 AM WEDNESDAY
 --------------------------------------------------------------------
 
 LOCATION                      FIRST ROUND            SECOND ROUND
                            PEAK GUST TIME PST     PEAK GUST TIME PST 
 ---------------------------------------------------------------------
 SOUTH WASHINGTON COAST...
   CAPE DISAPPOINTMENT.......66 MPH  415 PM 11/22    75   130 AM 11/23
   TOKE POINT NEAR RAYMOND...43      612 PM 11/22    63  1218 AM 11/23
   OCEAN PARK................58      500 AM 11/22    48   915 PM 11/22
   LONG BEACH................40      426 PM 11/22    51   116 AM 11/23
 
 NORTH OREGON COAST...
   ASTORIA...................81 MPH  248 AM 11/22    56   200 AM 11/23
   PACIFIC CITY..............79      739 PM 11/22    74   233 AM 11/23
   CAPE MEARES...............74      623 PM 11/22    92   338 AM 11/23
   GARIBALDI.................69     1236 AM 11/22    81   300 AM 11/23
   CLATSOP SPIT..............64      700 PM 11/22    69  1015 PM 11/22
   ASTORIA AIRPORT...........61      413 PM 11/22    64  1155 PM 11/22
   TILLAMOOK (CITY)..........60      738 AM 11/22    53   244 AM 11/23
   SEASIDE...................60      803 PM 11/22
   CANNON BEACH..............62      507 PM 11/22
   TILLAMOOK AIRPORT.........54      155 AM 11/22    55   355 AM 11/23
   OCEANSIDE.................                        55  1044 PM 11/22
   TIERRA DEL MAR............                        58  1129 PM 11/22
 
 CENTRAL OREGON COAST...
   SEA LION CAVES............81 MPH  258 AM 11/22    
   FLORENCE SIUSLAW JETTY....76      140 AM 11/22
   LINCOLN CITY..............75      630 PM 11/22    76   951 PM 11/22
   CAPE FOULWEATHER..........74      450 PM 11/22
   NEWPORT (YAQUINA BRIDGE)..68      625 AM 11/22    71   439 AM 11/23
   YACHATS...................67     1220 PM 11/22    47   436 AM 11/23
   CAPE FOULWEATHER..........66      732 AM 11/22    66  1037 PM 11/22
   NEWPORT JETTY (C-MAN).....64      800 PM 11/22    51   200 AM 11/23
   NEWPORT AIRPORT...........59      715 AM 11/22    53   155 AM 11/23
   DUNES.....................53      804 AM 11/22
   GLENEDEN BEACH............66      853 AM 11/22
 
 COAST RANGE...
   MT. HEBO OREGON...........97 MPH  427 AM 11/22    85  1234 AM 11/23
   ROCKHOUSE RAWS............74      912 AM 11/22    57   612 AM 11/23
   JEWELL OREGON.............67      414 AM 11/22
   ROCKHOUSE RAWS............64      712 AM 11/22
   CEDAR CREEK RAWS..........55      710 AM 11/22    50  1110 PM 11/22
 
 INTERIOR LOWLANDS...
   MCMINNVILLE AIRPORT.......45 MPH  718 PM 11/22 
   SALEM AIRPORT.............40      900 AM 11/22
   MCMINNVILLE AIRPORT.......40      619 PM 11/22
   FOREST GROVE..............40      730 PM 11/22
   AURORA AIRPORT............39      900 AM 11/22
   EUGENE AIRPORT............36      327 PM 11/22
   PORTLAND AIRPORT..........35      845 AM 11/22
   VANCOUVER AIRPORT.........32      557 PM 11/22
   KELSO AIRPORT.............30      635 PM 11/22
 
  *WIND SPEEDS REPORTED IN MPH
 

Washington was very windy as well, but I couldn't find any statistics posted on the NWS Seattle page. Nevertheless, Bellingham had a gust to 70 miles per hour Tuesday morning, which is pretty incredible. Sea-Tac's all time highest gust was 69 miles per hour back in the Hanukkah Eve Storm of December 14-15, 2006.

Now, let's talk about the current weather situation.

The National Weather Service for Seattle has issued a ton of warnings for our incoming storm! Winter storm warnings for the Cascades, high wind warnings for the coast and north interior, and storm warnings for the offshore waterways into the Strait of Juan de Fuca, around the San Juan Islands, and heading up into the Strait of Georgia. Take a look at the satellite image below, and you'll see the storm that is currently causing all of this weather mayhem.

01:30 pm PST Thu 24 Nov 2011 - West Coast 8km resolution water vapor satellite

The storm, a mature 972 millibar low heading up into Northern Vancouver island, is much faster than the previous storm, so the rain should pass through in the next couple hours, and the winds will calm down rapidly everywhere by 10 P.M., with many locations improving sooner than that. For current Thanksgiving travelers, the biggest problem will be snow over the Cascades, which will not let up until Friday morning. The latest model from the UW indicates anywhere from 10-18 inches above 2,500 feet or so. 

Valid 04:00 am PST Fri, 25 Nov 2011 - 24hr Fcst - UW 12z 4/3km 24-hour snowfall

Snow has started falling in the Cascades, even at Snoqualmie Pass.

Snoqualmie Pass always seems to get hammered on Thanksgiving... I can remember writing blog posts in the past about this. If you must drive over the pass, drive slow, bring chains, and be prepared for delays.

Have a nice Thanksgiving!

Charlie Phillips

One Storm Down, Another To Go

Wednesday, November 23, 2011
9:23 A.M.

The Pacific Northwest has seen incredible amounts of rain over the last 48 hours. A stationary front stalled over our region and directed relatively warm, moist air over our region, giving us heavy rain and strong winds, especially further south along the Oregon coast. In the lowlands, anywhere from 2-6 inches of rain fell. The Hood Canal area saw the heaviest rain, receiving up to 6 inches in spots from this storm. Even the UW campus has see around 2.5 inches of rain in the last 48 hours.

One of the most fascinating aspects of this storm was how we could see it on the coastal radar. Remember how I talked about that "thin band of heavy rain"? Check this image out.

11:25 pm PST Tue 22 Nov 2011 - Langley Hill Radar

If you look off the coast, you can see a very heavy band of precipitation off the Washington coast stretching into the Olympic Peninsula. This band actually stalled over this area for around 2 hours last night. If this happened in Seattle, catastrophic flooding would have resulted. The last time something like this happened in Seattle was between 4 and 5 P.M. on December 14, 2006, where Seattle received around an inch of rain in one hour. 

Seattle has seen some urban flooding, but the rivers have seen more. Although this wasn't a major flooding event for the rivers, as snow levels didn't rise super high, some rivers did see some flooding. Most of these rivers are still rising, and the graphic below shows their expected crests. The Skokomish River is expected to experience major flooding, and the Stillaguamish will experience moderate flooding. The Chehalis, at this point, looks to only experience minor flooding, as less rain fell than forecast over the Olympics. If snow levels were higher with this storm, I'm sure that most rivers in Western Washington would experience flooding, with several getting to major flood stage.

Another big aspect of this storm was the wind it brought to the Oregon Coast. It was breezy here, but the Oregon Coast experienced some scarily strong winds. The model below is from last night and shows the expected winds at 1 A.M. this past morning. The winds have since died down, but they are still strong from the central Oregon coast southward.

Valid 01:00 am PST Wed, 23 Nov 2011 - 9hr Fcst - UW 00z 12km WRF-GFS 10m wind speed, SLP

50 knots sustained! That is approaching hurricane force, and there were certainly hurricane-force gusts. I'll get the highest gusts from this storm later when I can find them online. 

On Thursday, we'll have to deal with another batch of heavy rain, wind, and mountain snow. This system will be weaker than the last one and will move by much more quickly, but it will still be a big November storm and will give us some pretty gnarly weather. 

The latest model run shows some very strong winds for the coast, with sustained winds reaching 45 knots. The north interior will also get blasted as well. A storm warning is in effect for the coast, and the north interior has a storm watch. We'll have to watch the next model runs closely.

Valid 01:00 pm PST Thu, 24 Nov 2011 - 33hr Fcst - UW 12z 4km WRF-GFS 10m wind speed, SLP

For travelers, the  biggest problem this storm will pose is a threat of significant mountain snow.

Valid 04:00 am PST Fri, 25 Nov 2011 - 48hr Fcst - UW 12z 4km WRF-GFS 24-hour snowfall

The snow level will be around 2,000 feet, and models are showing up to a foot of snow in places. I would not be surprised if these amounts turned out to be higher though.

Class in 3 minutes, gotta go!

Charlie

Snow in the Mountains

Tuesday, November 22, 2011
10:18 A.M.

This has got to be another quick post... I have class in 12 minutes, and I need to walk over there as well.

This isn't quite the "classic" setup for flooding in Western Washington. The reason? The snow levels are too low.

Many of our major flooding events have snow levels over 10,000 feet. Right now, it is absolutely dumping in the mountains, with snow levels around 6,000 feet in the south and 3,000 feet in the north. The Cascade passes, however, are seeing snow due to an easterly pass flow, keeping temperatures cooler there.

 Take a look at Snoqualmie Pass! I wouldn't be surprised if it opened by Thanksgiving.

Eventually, this snow will shift to rain later today into Wednesday, and that presents a lot of problems for avalanches. The rain will put a lot of additional stress on the snow layers and act to lubricate it, making it more conductive for sliding.

This is for Tuesday and Tuesday night at Snoqualmie Pass, with the red denoting high avalanche danger and the black denoting extreme avalanche danger. The Northwest Weather and Avalanche Center had this to say:

"Tuesday and Tuesday Night: Avalanche danger becoming extreme above 5000 feet and high below. Natural avalanches are certain with large to very large avalanches in many areas. Avoid all avalanche terrain."

The passes will likely be closed for avalanche control.

One more thing... Seattle is not seeing heavy rain right now, as the band has shifted south. However, we will see heavy rain by noon as the band shifts northward again, and it will stick around until Wednesday morning. Overall, southwest Washington looks like it will receive the heaviest blow from this storm.

Gotta go!
Charlie

Thin Band of Heavy Rain

Monday, November 21, 2011
12:03 P.M.

Valid 01:00 pm PST Tue, 22 Nov 2011 - 33hr Fcst - UW 12z 4km 1-hour precip, 10m winds

I just got out of my atmospheric sciences class, and I want to talk about a specific feature associated with this front that will make a huge difference in determining which areas get the greatest rainfall. If you look very closely at the model above, you can see a very thin line of extremely heavy rain. This image shows the rain pointed right at us midday Tuesday. This band is expected to move around a bit, but not a whole lot.

The bottom line is that the heaviest rain totals will be found where this specific band hits. If you look closely, you can even see some greens, which denotes rainfall amounts from .64 to 1.28 inches in ONE hour. That's incredible. Much of the band is blue, which means around a half inch an hour. The rainfall rates weaken over the Puget Sound area, but they are still very high. The Seattle area will probably experience some urban flooding from this storm, but the results could be much worse if this band stalls over our area.

At this point, it looks like the rain will start to impact our area in force by 3 A.M. Tuesday morning. You can see that heavy band of precipitation over the Olympic Peninsula.

Valid 03:00 am PST Tue, 22 Nov 2011 - 23hr Fcst - UW 12z 4km 1-hour precip, 10m winds

That band will sweep over us a couple hours later.

Valid 06:00 am PST Tue, 22 Nov 2011 - 26hr Fcst - UW 12z 4km 1-hour precip, 10m winds

After this, the heaviest precipitation will dip south for a bit (although we will still be getting rain), but that band looks to head back up into the general Puget Sound vicinity by noon and hang around until Wednesday morning.

Last, let's look at the 48-hour precipitation totals expected over the area.

Valid 04:00 pm PST Wed, 23 Nov 2011 - 60hr Fcst - UW 12z 4km 48-hour precip, 10m winds 

Right now, it looks like the North Cascades and Olympics will be the hardest hit. Mt. Rainier looks pretty rainy as well. In this model run, the Central Cascades look ok as far as flooding goes. This is not the "classic" pattern for flooding in the Central Cascades, which get more precipitation from a more westerly flow. Nevertheless, it will be close for some spots, and I encourage people who live there to prepare for the possibility of minor flooding.

I'm particularly worried about the Chehalis River. The models point towards some especially heavy rain in the Chehalis River drainage. In the December 2007 flood event, a 20-mile stretch of I-5 from exit 68 to exit 88 was closed because floodwaters from the Chehalis inundated it with up to 10 feet of water in spots. While we won't see 10 feet of water on the road this time around, we could easily get a couple feet, causing I-5 to be closed for Thanksgiving travel. This  would surely put a wrench in many people's holiday plans.

I've done all my homework for the next several days, so I'll be updating this blog as more information about this coming storm surfaces.

Thanks for reading!

Charlie

Storm Looking Even Bigger

Monday, November 21, 2011
10:07 A.M.

I have to be brief, as I will have classes in 20 minutes, but I thought I'd give you an update on the major storm that will impact us tonight into Wednesday. I looked over the model runs this morning, and it looks as if the storm is now forecast to bring even more rain into the lowlands. Additionally, it will still be very windy on the coast, particularly the Oregon coast, where sustained winds of 40 knots with gusts up to 70 knots in isolated places will pound the area for up to 24 hours.

Today, I was browsing the UW atmospheric sciences website, and I found some early model runs from the beginning of December 2007 showing that massive storm that impacted us at the beginning of the month. For the sake of comparison to today's storm, I'll show them below.

Valid 04:00 am PST Mon, 03 Dec 2007 - 12hr Fcst - UW 00z 12km WRF-GFS 10m wind speed

This event was extraordinary. Note the sustained winds over 50 knots on the Oregon coast. Washington was also extremely hard hit by the storm.

The precipitation was also incredible... Seattle saw over 3.5 inches of rain in 24 hours. Bremerton, right across the sound, saw 10.78 inches in 24 hours! And some regions in the Willapa Hills saw over 15 inches of rain in 24 hours.

Now, let's look at the runs for today's storm.

Valid 01:00 pm PST Tue, 22 Nov 2011 - 33hr Fcst - UW 12z 4km WRF-GFS 10m wind speed

The winds, while extremely strong, are not as strong as the 2007 event, and will mainly occur on the Oregon Coast.

Just a few minutes left... let's look at precipitation.

This model is showing up to 5 inches of precipitation for the Seattle area in 24 hours. If this verifies, this could set numerous records for 24-hour rainfall totals across the lowlands. I will be monitoring this situation very, very closely. As far as flooding goes, the Skokomish River off the Olympics is certain to flood. Many other rivers will flood as well... I'll give you more details as the event unfolds.

Gotta run!

Charlie

Major Storm On Tuesday

Sunday, November 20, 2011
8:43 P.M.

Carol Snider - Urban Flooding in Seattle - December 3, 2007

Approximately four years ago, one of the strongest storms to ever hit our area, the "Great Coastal Gale," brought hurricane-force winds to the coast and major flooding throughout the area. While the inland areas didn't get hit quite as hard, the storm was still one to remember. For old time's sake, I'll show you the satellite picture of the storm approaching the area.

07:00 pm PST Sun 02 Dec 2007

While we probably won't see a storm of this magnitude for many more years, we will see a major storm bringing high winds and flooding rain approach us. A fast-moving front will come through the area Monday morning, bringing a brief dose of heavy precipitation and brisk winds to the coast, but this will not be the main event. On Monday night, the biggest storm we have seen for all winter will slam into the Pacific Northwest. This storm will generate very strong winds, particularly for the coast, and will dump heavy rain over much of the area. To make matters worse, this storm is expected to be a slow-mover, and it is possible that it might not clear the area until Wednesday morning. 

For most of us, heavy rain will be the primary concern with this storm.

Valid 04:00 am PST Wed, 23 Nov 2011 - 60hr Fcst - UW 00z 12km WRF-GFS 24-hour precip

Look at all of that rain! The models indicate that much of Western Washington could get inundated with 2-5 inches of rain from Tuesday morning to Wednesday morning. 

With all this rain comes flooding concerns, and it will be a close call for many of the area rivers. Although the mountains will get even more rain than the lowlands, the amounts in the models are actually relatively low for an event like this. This seems to be due to the lack of orographic enhancement over the mountains, particularly the central Cascades, which generally get more rain from a westerly flow rather than a southwesterly one. The Skokomish is likely to see major flooding, as it is the most flood-prone river in the state. Many other rivers may see minor to moderate flooding. Thankfully, at this point, it doesn't look like a historic flood event. 

But it will be very, very wet.

Now, let's look at the winds. 

Valid 01:00 am PST Tue, 22 Nov 2011 - 33hr Fcst - UW 00z 12km WRF-GFS 10m wind, SLP

The model above shows the winds expected over our area at 1 A.M. Tuesday morning. You can see two general areas receiving high winds... the area immediately south of the low, and the larger area in ahead of the stationary front off our coast. Since this front will not move much, the area of high winds will not move much either. The result will be a prolonged high-wind event for the coastal strip of the Pacific Northwest. Inland areas will also get windy, particularly the north interior, but the coast will receive the brunt of this storm with respect to wind.

The rest of the week looks rather exciting as well. On Thursday, the model shows a small but intense area of low pressure making landfall at the mouth of the Columbia. This could spell high wind for the Portland area, and will need to be watched carefully.

Valid 10:00 pm PST Fri, 25 Nov 2011 - 126hr Fcst - UW 00z 12km WRF-GFS 10m wind, SLP

The bigger story, however, is that the model I have been using for this post indicates that another major storm similar to the one we will see Tuesday will impact our area over the weekend, giving high winds to the coast and heavy rain throughout Western Washington

04:00 am PST Sun, 27 Nov 2011 - 156hr Fcst - UW 00z 12km WRF-GFS 24-hour precip

We'll have to keep an eye out for this one as well, but not all of the models show it at this point. In the meantime, button down the hatches and get ready for Tuesday. It looks as though the storm season has finally arrived.

Charlie

A Snow Non-Event

Friday, November 18, 2011

10:25 P.M.

Various places around the area have seen some snow tonight, even places in Seattle. However, our snow looks over for now. The models were showing a low pressure system coming in around Grays Harbor overnight and giving us additional snow showers, but this low pressure system is much weaker than the models showed it. Apart from being much less precipitation, the weaker low has also failed to bring in a cool northerly flow. In fact, the snow level is around 1,000 feet or so right now, clearly not conductive for snow.

The models this morning were actually pointing to some snow over our area, with some quite heavy amounts further to our south. These were some of the first model runs that were actually pointing to snow over the lowlands. Take a look at the UW high-resolution GFS run from this morning. Look at all the snow, particularly to our south!!!

 Valid 04:00 pm PST Sat, 19 Nov 2011 - 36hr Fcst - UW 12z 4/3km WRF-GFS 24-hour snowfall

Some places in the south Sound and away from water were expected to get up to 8 inches! I was super excited, and the National Weather Service issued snow advisories for the South Sound. Even then, they were playing it safe, with their snow advisories predicting 1-3 inches of snow for the south sound. Seattle proper was not included in the snow advisory, but this model still showed 1-2 inches of snow for Seattle, with the higher amounts towards the south. 

Then, the model runs came out tonight, and showed absolutely no snow for Seattle, with much lighter amounts to the south.

 Valid 04:00 pm PST Sat, 19 Nov 2011 - 24hr Fcst - UW 00z 4km WRF-GFS 24-hour snowfall

Most of you reading should have a frowny face on by now. When I saw these models, I know I sure did.

Places near the sound are now predicted to get no snow. Seattle will not see accumulating snow tonight, and I am doubtful that the places with snow advisories will see the 1-3 inches predicted. I'd predict trace-1 inch amounts in the places that do see snow. 

This snow "event" may have not panned out for most people, but we will see some interesting weather next week. Models show flooding off the Olympics and high winds on the coast next week. I'll update this blog tomorrow with more information on the wild weather we can expect next week. Thanksgiving week is statistically the stormiest time of the entire year, and I think we'll get more than our share this time around.

Thanks for reading!

Charlie

Snow Looking a Bit More Likely

Thursday, November 17, 2011

12:51 P.M.

I've got some great news for all you snow lovers! The new 12z model runs came out this morning, and both of our high-resolution models at the UW are pointing to a bit of snow in the Western Washington lowlands! This is the first run that has really shown some snow, so I am not completely sold on the idea yet, and the snow  predicted is pretty light and spotty, with Seattle not getting much at all. However, it is an encouraging sign. The models late this evening will give us a better idea on whether we can expect to see snow or not.

Yesterday was a pretty interesting day for weather. We saw some pretty gusty winds and heavy rains over the area. I live on the 8th floor of a south-facing dormitory, and the winds were really blowing last night! I decided to open all the windows for a couple minutes, and all of my papers were flying all over the place. It was pretty cool.

Here is some data from the UW atmospheric sciences for the last 24 hours as of 1 P.M. PST today. Click on the image to enlarge it.

You can see some pretty strong winds, with gusts approaching 30 knots! Also, look the beautiful pressure trace. You can see a clear minimum from 10 P.M. last night.

Now, let's look at some of the snow forecasts for our area. Right now, it seems our best shot for snow is Friday night into Saturday morning.

Valid 10:00 pm PST Fri, 18 Nov 2011 - 42hr Fcst - UW 12z 4km WRF-GFS 3-hour snowfall

As a low pressure system passes to our south, northeasterly winds will start to flow out of the Fraser River Valley. As these winds hit the northeast side of the Olympics, they will rise, creating clouds and snowfall near Sequim. Sequim is usually the driest place in Western Washington, but it looks like they'll be one of the snowiest places in the next couple days!

Valid 04:00 am PST Sat, 19 Nov 2011 - 48hr Fcst - UW 12z 4km WRF-GFS 3-hour snowfall

As we get into Monday morning, things become more interesting. We have snowfall north and south of Seattle. Things could change though, so this situation bears watching.

Heavy rain is still on tap for next week, though, and if the models are correct, many rivers off of the Olympics will flood.

Valid 04:00 pm PST Tue, 22 Nov 2011 - 132hr Fcst - UW 12 12km WRF-GFS 24-hour precip

Look at that! 5-10 inches of precipitation on the Olympics! Right now, Seattle doesn't look too bad, but that could change if this band of moisture moves a little bit south. This is a classic "Pineapple Express" event, as a large stream of subtropical moisture looks to be aimed right at the Pacific Northwest. The snow levels with this system will be high, which is not good for flooding concerns or ski resorts.

I got to go now, thanks for reading!

Charlie

Moderate Rain Now, Lumpy Rain Friday, and Heavy Rain Tuesday

Wednesday, November 16, 2011

2:59 P.M.

Currently, we are seeing some moderate rain as a pretty strong system comes through. In addition, we will see some gusty winds tonight, as we will have a strong pressure gradient over us from this system. Take a look at the winds forecast at 1 A.M. PST tonight. You can see strong winds in most places, but there is an area of winds that are nearly calm over the Puget Sound region. If you can guess what this is, you are a true weather nut.

Valid 10:00 pm PST Wed, 16 Nov 2011 - 18hr Fcst - UW 12z 4/3km WRF-GFS SLP, 10m winds

It's a convergence zone! To give you proof, look at the 3-hour precip at that time, and see the convergence zone over central Whidbey Island.

Valid 10:00 pm PST Wed, 16 Nov 2011 - 18hr Fcst - UW 12z 4/3km WRF-GFS 3-hour precip

This storm is passing through though, and the story for Friday is the threat of "lumpy rain." I call it "lumpy" because it is basically all rain except for a little bit of snow that hasn't quite melted, so it isn't completely  liquid.

See that penguin above? He is a sad, sad penguin. Even though the models weren't quite showing it, he was hoping for some snow. Now, however, those snow chances are dwindling, and it looks as though he's going to have to deal with a lumpy rain.

The bigger story is the heavy rain event that will occur on Tuesday. It is too early to tell if there will be flooding on some of the area rivers, but it will be very wet regardless. Take a look at the 24-hour precip ending at 4 P.M. PST Tuesday.

Valid 04:00 pm PST Tue, 22 Nov 2011 - 156hr Fcst - UW 12z 12km WRF-GFS 3-hour precip

Pretty wet for us, with the Olympics getting particularly hard hit. This situation bears watching.

I wrote this post super super quick, because I have to attend a meeting on majoring in atmospheric science in 11 minutes! Seeya!

Charlie