Nice Weekend and LA Fires

This weekend will be better than average. There are some clouds and a few sprinkles over the northern portion of the state, but they will slowly push northward later today (see computer model precip forecast for 1 PM today). The showers and clouds will be even further north tomorrow as high pressure builds--so for most of western Washington we will see partly sunny skies and temps in the 50s.

In LA there are major wildfires associate with Santa Anna conditions...strong offshore flow that is prevalent this time of the year. Why? In the fall, cool, high pressure systems often push down into the intermountain west. This produces an offshore-directed pressure change (lower pressure offshore) that accelerates winds to the east (see surface pressure graphic). The winds are particularly strong in canyons and gaps. Take a look at the visible satellite image from this morning..you can see the plume of smoke from the fires.

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The Weekend

The weekend looks generally dry over the southern portion of the state, with a chance of showers over the north. This is particularly true on Saturday when a very weak frontal zone will be stretched over the northern portion of the State. This band will tend to move northward on Sunday...so I expect that to be the better day. Temps in the mid 50s.

Right now a weak warm front is moving northward up our coast producing clouds over the western portion of the state (see sat pic). Go south for sun!

Monday and Tuesday should remain dry and temperate.

Reminder: I will be talking at the downtown library at 2 PM on Saturday if anyone is interested in attending.

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A Major Improving Trend

The heavy precipitation event is over now...and some of the rainfall totals in the mountains were impressive: over the past 48 hrs this is how much rain fell:

Snoqualmie Pass 8.66 inches
Stampede Pass 8.60
Rainier Paradise 6.74
Hoh Ranger Station 6.40

while at Sea Tac is was only 1.15 and at the UW about .5 inch. A wonderful example of what happens here under strong westerly flow--lots of precipitation on the western slopes of the mountains and a mega rainshadow over the lowlands downstream of the Olympics and the Mts. of Vancouver Island. We did get a Puget Sound convergence zone forming late yesterday and it was evident this morning (see radar and sat picture). As westerly winds move around the Olympics they converge--providing upward motion and a band of clouds and often precipitation.

The CZ will weaken today, with party clouds skies...and yes, even some sun. By the air mass is cooler and we will stay in the lower 50s in general.

Just a note: I will be on KUOW tomorrow at 9 AM for an hour and then will give a talk on local weather (and sign my book) on Saturday at 2 PM at the downtown (central) Seattle Public Library.

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Flooding and Rainshadow

Today I biked to the UW and was perfectly dry. No rain gear needed and the temperature was so warm I had to remove my sweater. In contrast, it is pouring on the coast, over SW Washington, and in the Cascades, with a number of locations getting close to .5 inches per HOUR. The reason: a very evident rainshadow to the lee (east) of the Olympics (see radar image). There is also rainshadowing in the lee of the mountains of Vancouver Island...so the San Juans and Bellingham are doing well. Why is the rainshadow over us and not Sequim?...because the winds are westerly. Usually during wet situations it is southwesterly and rain shadow is centered to the NE of the Olympics. The high resolution computer models had the rainshadow in it yesterday (see the graphic of an 18-h forecast)....we have really come a long way.
The computer models suggest the heavy rain will slowly sink southward during the day and the area should dry out after dinner. Then we are dry until Friday when a weak warm front will bring some light rain to the northern part of the State and clouds over the rest.

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The next two days will be very wet in mountains, but much less so in the lowlands. Winds will also pick up later today...but once we get through this, a very much improving trend is ahead.

The satellite image shows the story, one (weak) disturbance is over us now, and a second, beefier one, is moving rapidly our way. Note how the clouds of the second system stretches thousands of miles to the SW to somewhere around Guam. This moist flow will be heading directly towards us this evening.

Today will really be no big deal...this weak system is moving through with only some light rain and modest winds. Good day to rake those leaves...particularly those that might clog a drain. The serious rain will start tonight after 10 PM and will go into the afternoon tomorrow. The mountains will be hit hard (see the forecast graphic for 24-h rain ending 4 AM tomorrow am), but the central Sound will be rainshadowed by the Olympics. The rainshadow is really amazing in the forecast precip--particularly on the northern portion of the Kitsap...it will be hardly raining there. This is a good example of something that makes weather so much fun around here...the startling contrasts of our region. It will raining 5-10 inches on the SW side of the Olympics but nearly dry on the lee side.
Winds...strong southeasterlies in NW washington right now..gusting to 30-40 mph..that will weaken later today. Breezy tomorrow from the south...but no major windstorm. Then strong westerlies in the Strait and N. Sound on Thursday morning

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Hell, Then Heaven

Today will be pleasant break in the weather with some sun and temps getting into the mid-50s. But things are going to change in a big way.

A very moist pattern will set up for a few days and flooding will probably occur along some of the local rivers. A warm front will approach the region tomorrow am...and we should be cloudy and raining on Tuesday morning. This will bring a warmer air mass in and the winds will strengthen during the day from the south. Particularly strong SE winds over NW Washington from Everett, across Whidbey, into the San Juans. The mountains will get several inches from this first pulse. The rain will lessen a bit in the afternoon, before the second and stronger system hits. This one will be very wet and some windward slope regions will be hit by 5-10 inches. You can bet on river flooding. The saving grace for the central and northern sound is that we will be somewhat rain shadowed because the winds will have a large westerly component.

The graphic you see shows the 24-h rainfall ending Wednesday morning at 4 AM. The reds are 5-10 inches--enough to cause the rivers to really surge. What makes this event even more of a problem is that is the two rain events have very little separation...the soils will be saturated from the first and then they will be hit hard by the second.

Wednesday morning will see drying. The end of the week should be relative dry with normal temps and a huge ridge of high pressure builds in Friday and Saturday (see figure for Friday upper air pattern and huge ridge along the west coast). The weekend may be extraordinarily nice...dry and fairly warm. But it is too early to be sure about this.

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A few showers today

A weak trough is over us today and you can see the associated clouds in the the infrared satellite picture. The radar shows light showers moving through in the radar (pink colors are light rain). As this trough moves through expect improvement today with rain ending most lowland locations by lunch (although there could be a few isolated light showers). Higher probability of showers in the mountains. Yesterday ended up warmer than expected, reaching into the lower 60s..but not today...should only see mid 50s.
There is a front looming offshore (see satellite photo) and although it is not a strong one, it should bring clouds and showers tomorrow. Bu ta stronger system will come in starting Tuesday as the jet stream becomes directed straight towards us (see upper level chart below). This is for roughly 18K ft (actually 500 millibar pressure) and the winds are parallel to lines and the closer the lines are packed the stronger the winds. The jet stream is associated with the band of packed lines, and stretches into the Pacific.

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Sunday Break

Well, the continuous moderate rain is over, so the rivers should start to recede, but one more strong precipitation line is about to hit at 8:30 AM (see radar). There will be moderate rain for roughly an hour as this line passes through and then by lunch we will be in sunbreaks and light showers. Temperatures should also be cooler today as we get into the postfrontal air behind this line.
There is a fairly strong low center offshore right now (look at swirl in the satellite pictures and the sea level pressure analysis), but this low will rapidly weaken as it moves in...no big windstorm in the lowlands. But it is quite windy now in NW washington (strong southeasterlies gusting to 30-40 mph) and strong wind winds along the coast (with Destruction Island reaching 50 mph).
So later this afternoon should be much better everywhere with only some showers..highs in the low 50s. Tomorrow and Monday will continue the pattern of sunbreaks and a few showers...not bad for November. Tuesday the torrent returns....but more on that tomorrow.

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The Worst Will Soon Be Over in Seattle

We are now in a very warm, wet pattern, with rain falling at all elevations. At Sand Point in Seattle we have a device called the profiler that continuously measures wind and temp above (see figure). Time increases from right to left, the heights are in meters (1500 m is roughly 5000 ft), temps are in red and roughly 15C in the lower atmosphere right now . The winds switched from southeasterly to southwesterly and are now moderately strong.
During the last 24 hr, the lowlands have received 1-2.5 inches, with Sea-Tac getting a little over 2 inches. Shelton and coast roughly double that and exposed windward mountain slopes between 5 and 8 inches. Look at the radar (see below)--the rain now is mainly north of Olympia and there is a wonderful rain shadow. The satellite shows moisture streaming in from off the Pacific, but the tail of this pineapple express appears to have weakened (see photo). The National Weather Service has flood watches out for a number of rivers of the Olympic Peninsula and north-central Cascades.

You can think of this pattern like a hose, one that shifts north and south in time. Computer models indicate that the hose will shift a bit north today and the rainfall should back off this afternoon...so I suspect the worst will be over here by midday. Then we will enjoy intermittent showers with some breaks. A cold front comes through late tomorrow...rain will pick up with it, but after its passage we will definitely be in the shower regime. Temps will cool and the higher mountains will be back to snow. Sunday and most of Monday will be a break...but we will be in an active pattern next week after that. This IS November.

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Pineapple Express

We are now about to enter a period of very wet weather, and I can't help remember two years ago when we had extraordinarily rain and Mt. Rainier park sustained terrible damage.

A warm front is now approaching our area and rain has spread over the region (see radar image). It is raining off the coast and in that triangular area over the Olympics, but the Olympics are blocking it (why we need a coastal radar!). Also, you can see the rain show to the NE of the Olympics. A stream of moisture is entering our region, with roots in the subtropics (see satellite photo)..the pineapple express.

The warm front will move through this morning and temps will increase, winds will increase, and the rain in the mountains will rev up as moist, strong, southwesterly flow ascends the terrain. Two images of forecast three hour rain (in hundredths of an inch) are shown here for two different times. Note that the Olympics and north-central Cascades get the worst of it.
The 24h precip amounts forecast ending tomorrow morning and saturday morning are shown here. Huge amounts over the mountains--the red areas are between 5 and 10 inches! Some areas in the mountains might get 10-20 inches and flooding is a real threat on several river drainages (the National Weather Service has flood statements out already).

And there is more...we will have some windy periods...and particularly strong southeasterlies over N Whidbey Island and the San Juans (see figure). In my new book I describe why this occurs.
Anyway, November is here and that is when we get the big weather action.

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The Warm Front Cometh

Now that I have recovered from following the elections, back to weather.

Today should be a very pleasant day..cool, dry, with temps getting into the lower 50s. But change is on the way! An usually strong warm front will move through early tomorrow AM. The air mass will become much warmer and wetter, winds will strengthen and turn to the southwest along the coast and aloft...with rain, sometimes of moderate intensity moving in. There will be rain to our south over Oregon today...but it won't reach Puget Sound until after dinner. The heavy stuff won't get here until 4-8 am tomorrow...and both Thursday and Friday will be wet. The mountains (particularly the Olympics and north Cascades) will get very heavy rainfall...with some locations hit by 5-10 inches over the next two days.

So what do you do? Head to Sequim! There will be a nice rainshadow there tomorrow--as is typical under rainshadow conditions. Take a look at the precipitation forecast for the UW high resolution weather predictions attached.

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Election Day Weather

It is raining quite hard over Puget Sound right now, but starting to dry out over the coast (see radar--green is moderate rain-- and satellite picture). The area of rain is associated with a weather trough of low pressure that will move through this morning....so by 9-10 am things should really dry out. As you see from the satellite picture there are some showers over the Pacific (speckled white stuff) and this will be moving in. However, the winds will switch to the NW on the coast after the system moves through, so Puget Sound will experience considerable rain shadowing off the Olympics. So today will not be bad after the rain ends, generally dry with a few isolated showers. The only real rain might be in a Puget Sound convergence zone that could form later in the afternoon north of Seattle.
The air mass is cooling down and the freezing level is dropping,,,the result will be increasing snow in the mts at pass level and above....this is already happening at Stevens pass (see photo). There could be as much as a half foot in the higher passes; NW flow is favorable for snow..so snow showers could extend throughout the day up there.
Tomorrow looks dry..until a warm front comes in during the evening...so rake those leafs then!
Today is the election of course...and one race I am following is for Superintendent of Public Instruction. The group I am a member of ...wheresthemath.com.. is supporting Randy Dorn, who we think will have a major positive influence on the serious math education problem we have in this state. We have had unending problems with the current leadership--Terry Bergeson.

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Weather and Elections

An article in the Journal of Politics analyzed the influence of weather on elections...and the effect is significant. Heavy rain and snow really lessens voting and it appears that such inclement weather influences Democratic voters more than Republicans. The weather map you see shows precipitation, pressure, and temperature at about 5000ft (which meteorologists like to look at). Most of the country will be dry or experience very light rain at most...and most of the eastern 2/3rd of the U.S. will be unusually warm. Key battleground states like Ohio, Pennsylvania and Florida will be nice--so that is good for Obama. Virginia will be wet..good for McCain. Our area..the Pac NW will have rain in the am...but we are firmly in the Democrat column...so that won't make a difference for the Presidential race.
Today will have some mixed showers and sun...with more steady rain tonight...followed a day of sun and showers tomorrow.

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Well, if you were going to go hiking today...forget it (see the picture). It will be raining most of the day in the mountains. A weather disturbance is just moving through (see the radar picture) and precipitation has lessened over central Puget Sound). But a look at the high resolution satellite picture show shows showers ready to rotate into Puget Sound. There should be some rainshadowing north of Seattle...and everywhere will see some breaks. This is the traditional postfrontal on and off showers we love so much. You can protect yourself for a while by looking at the radar imagery available at the UW atmos web site, the NWS web site, or many local tv stations.
Another disturbance comes in Monday. Right now things don't look bad for Tuesday...generally dry during the day in the lowlands.

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Weekend Weather

This is going to be a typical early November weekend...clouds and showers...but nothing serious over western Washington...however, something VERY serious is occurring offshore. Take a look at the satellite image. The swirl offshore is a fairly intense low pressure center that will be moving northward offshore..strong winds and large waves will be associated with it...but it is too far away to greatly influence our weather. Take a look at the computer forecast for 11 PM tonight...the lines are isobars, lines of constant pressure. Intense low center with large changes in pressure...which produce strong winds. The only strong winds around here will be the southeasterlies stretching from Whidbey Is to the San Juans (see forecast of wind speeds for tomorrow morning attached). And along the coast. The red and blues are the really strong stuff.
It is relatively dry right now in Puget Sound, but that will change later this morning as the front rotates in...so expect showers later this morning and afternoon. Another disturbance rotates through tomorrow...so more showers and clouds. And it should be breezy tomorrow as the low moves north of us...so the leaves will be coming down.

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