Want Warm Water--Get a Boat!

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It is not unusual during summer to view a satellite image like the following, with a narrow sliver of low cloud along the  Northwest coast.  Why does this occur?

MODIS satellite image on August 12th

The answer:  cold water along the coast due to ocean upwelling (cold water coming up from below).  It is not usual during the summer to have coastal water temperatures 10F or more cooler e than what we observe 0-15 miles offshore.

Let me give you some recent examples.  Here is the latest National Weather Service sea surface temperature (SST) analysis for today...notice the cold temperatures from San Luis Obispo on the southern CA coast to our area, with the coldest temps along the northern CA coast.

 We can take a closer look off the Oregon coast by viewing the SSTs forecast by the Oregon ROM ocean modeling system (I used the NANOOS web site to plot this).  Lower to mid-50s along the coast while lower 60s are waiting 100 miles offshore.

Or take a look at the last NOAA SST analysis for the NW coast.  A veneer of cold water follows the coast.


Buoy 27 is found right off the Oregon/CA border and temperatures there have been dropping into the lower 50s.
 But head out to Buoy 46006 and temperatures in the in sultry mid to upper 60s.

The offshore water is warm enough for albacore tuna, so a number of Washington and Oregon fishing charter companies head offshore 10-30 miles to give anglers a chance to bring in some tuna.

Image courtesy of Deep Sea Charters, Inc. of Westport

Coastal cold water is typically a warm-season coastal ocean feature around here.  This is because the East Pacific High moves northward during the summer, producing northerly winds along the coast.  These northerly wind push the coastal water southward, but the Coriolis force then acts on the moving water, giving it a torque to the right (offshore).  Move surface water offshore and water comes up from below to take its place (see figure).

 

Sea-Tac Heat

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Roughly a year ago, I provided some evidence that the construction of the third Sea-Tac runway, with the ancillary taxiways and removal of a vegetated slopes, has resulted in an anomalous warming at the airport during warm summer days, particularly when the winds are from the north or northwest.  This is important for a number of reasons.  First, Sea-Tac is the spotlighted station on many local TV weathercasts (see image).  Second, it serves as a example of issues with our observational networks, where urbanization and construction can produce a warming signal distinct from the true warming of the general atmosphere.

Well, we had some warm weather recently...do we see the Sea-Tac warm anomaly?
For example, 4 PM this afternoon?  Here is a plot of nearby stations (KSEA is the airport).  72F at the airport (where the winds were north-northwest) and cooler for the nearby locations.



Or a few weeks ago, when the airport was 87F?  Again, nearby locations were cooler.



In the old days, Boeing Field, closer to the urban core of the city, was generally warmer than Sea-Tac.  But is that true now? Here is a plot of the temperatures at these two locations for the last four weeks.  Note that on the warm days (generally ones with lots of sun and northerly winds), Sea-Tac (SEA) was warmer than Boeing Field (BFI), often by several degrees.
Multiple such urbanization/development issues at locations around the world, and it is clear that it can obscure the true background temperature change signal that we are looking for.  Organizations, such as the National Climatic Data Center, have tried to develop algorithms to spotlight or remove such problems, but there success so far is mixed.  Satellite observations of temperature above the surface are a bit less problematic, although they have their own issues (like calibration of replacement satellites).

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I will talk about some of the above issues during my talk on Orcas Island on Wednesday.

First Frost and Tropical Storm Isaac

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Nights are getting longer now and with clear skies some locations, particularly east of the Cascades in low spots, are dropping into the 30s and even to freezing.


For example, at Turnbull National Wildlife Refuge, southwest of Spokane (see map above) yesterday morning (25 August),  there were 3 hours at or below freezing for the surface air temperature (taken at 2 meters) and a ground (surface) temperature of 29 degrees F:

25 TRNW1 cn 0600 40 0 TSFC=39 SR=0
25 TRNW1 cn 0700 38 0 TSFC=36 SR=0
25 TRNW1 cn 0800 37 0 TSFC=34 SR=0
25 TRNW1 cn 0900 34 0 TSFC=33 SR=0
25 TRNW1 cn 1000 34 0 TSFC=31 SR=0
25 TRNW1 cn 1100 32 0 TSFC=30 SR=0
25 TRNW1 cn 1200 31 0 TSFC=29 SR=0
25 TRNW1 cn 1300 32 0 TSFC=29 SR=0
25 TRNW1 cn 1400 36 0 TSFC=33 SR=49
25 TRNW1 cn 1500 55 0 TSFC=52 SR=200
25 TRNW1 cn 1600 60 0 TSFC=67 SR=378

And this morning, a famous cold spot, Meacham Oregon (KMEH), got down to at least 33F, and probably hit freezing between the hours.  This is air temperature- frost was undoubtedly seen on the ground in places.  Yesterday the high at Meacham was 78F...so you needed a tee shirt and jacket to be comfortable there.



 Meacham is cold because it is location in a high mountain valley (elevation around 3800 ft), allowing cold air sinking off the terrain to settle in the cold protected basin.

Finally, for those interested in Tropical Storm Isaac, it is becoming increasingly clear that Tampa and the western Florida peninsula will not get the brunt of it--some heavy rain squalls and winds gusting to 20-40 kts should be the worse they experience (see graphic).

The latest satellite image does not show an eye yet for this storm:

 The latest radar image from Miami shows bands of intense showers rotating around Isaac's center:

Isaac should intensify into a hurricane over the warm waters of the Gulf and could be packing 80-100 kt winds when it strikes Louisiana and Mississippi.  Remember, my profession's ability to predict track (where the storm will go) has gotten very good, but our ability to predict intensity has hardly improved over the past thirty years.  New Orleans needs to be prepared and the oil-rigs battened down.

Probabilities that the wind speeds will exceed 50 kt.

Probability of Hurricane-Force (74 mph or more sustained winds)

The Real Threat of Tropical Storm/Hurricane Isaac

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The media isn't talking about this much, but the real threat of tropical storm Isaac may be heavy precipitation and flooding....not winds and storm surge.

Recent model runs suggest the storm might stall over southern Lousiana, resulting in huge amounts of precipitation (storm totals of 12-24 inches in some locations).   Here is the latest storm total precipitation totals form the NWS GFS (78 hr total) and NAM (84 hour total) models for runs started at 1200 UTC this morning:


Pretty impressive precipitation.

 And here is a nice satellite image of Isaac at 11 AM with some observations plotted.  One report of 70 knots near the center.  No obvious eye at this time.  The lowest pressure observed is 987.8 hPa. 

The Winter Forecast and a Wimply El Nino

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The main tool used by meteorologists to predict the nature of the weather months ahead is the correlation of the temperature of the tropical Pacific ocean surface and the atmospheric circulation around the globe.  To put it another way, meteorologists use the correlation of the El Nino and La Nina cycle (called ENSO-El Nino Southern Oscillation in the business) with midlatititude weather.   This correlation is not perfect, but it is the most potent tool we have for predicting a few months ahead.

As with any good tool, you need to know how to use it, as well as its limitations. 

One key rule is: don't make your winter predictions too early!  A lot of research, including that of UW's Todd Mitchell, have shown that one really needs to wait until very late summer to have real skill for predicting the character of  the upcoming winter.  Thus, I like to wait until late September:  by this time we can have high confidence that we have a handle on the general nature of El Nino/La Nina for the winter months.  So I feel comfortable giving you a prediction at this point.  A second thing to keep in mind is that this tool is imperfect, explaining perhaps a third to a half of the winter variability. 

OK, enough caveats and warnings.  Let me give you the story! 

For the last two years we have been in a La Nina situation (colder than normal central and eastern tropical Pacific sea surface temperatures), which is generally associated with greater mountain snowpack, colder temperatures, and increased chances of lowland snow, particularly after Jan 1.  And generally it delivered---Cascade snowpacks have been high and our last two springs were dismally cool and wet.  But this year La Nina has collapsed and the tropical Pacific has warmed, leading to a weak El Nino.   This graph shows the sea surface temperature anomalies (differences from climatology, blue colder than normal, orange is warmer) for several tropical Pacific regions (the Nino 3.4 region is the most used) since October 2011.   We have a pretty wimpy El Nino at this point (anomalies only about .5C) and lately it has weakened substantially.

At this point in time, we would expect this winter to be an El Nino one, simply on the basis of persistence---since it takes a while for the ocean temperatures to shift. 

But we have more sophisticated tools. 

First, there are a series of models--some statistical, some simulating the ocean/atmosphere system--that provide a forecast of what is happening over the tropical Pacific.  Here is a nice collection that I accessed on the NOAA Climate Prediction Center website. Most of the models suggest a slight warming (increase in El Nino) this fall, followed by a slow weakening.  The definition of El Nino requires that the warm anomaly be at least .5C and we are just over that now and slide below it next Spring.  If the anomaly is between plus or minor .5C of normal then we are in a neutral or "La Nada" year.


The National Weather Service also runs their global coupled atmosphere/ocean model (the CFS) out many months.  Here is what it is showing.  Same wimpy, marginal El Nino, and on the verge of being a La Nada year.


But this El Nino/ENSO stuff is interesting perhaps, but what you REALLY want to know is what we expect for the upcoming winter, right?

First, the bottom line.   El Nino years tend to produce Northwest winters that are warmer than normal, drier than normal, with less than normal mountain snowpack and a lower probability of lowland snow.  They tend to be less stormy here, with more of the action going into California.

The greatest impacts are generally after January and the strength of the effect is dependent on the warmth of the tropical Pacific.   The following graphics illustrate the impact across the U.S. of El Nino's during January though March.  The first shows preciptation--a really modest decline over the NW and an increase over the southwest U.S.

 For temperature, warming over the northern tier of states.

The issue, of course, is that this is looks like a very weak El Nino at this point and the impacts will be thus attenuated.  The result:  less signal and thus less forecasting skill.

We could easily be a near neutral situation (La Nada) the end of the winter, and those can be interesting periods, since the biggest of the big events (floods, windstorms, even snowstorms) tend to occur in neutral years.

So keep your eyes on the tropical Pacific temperatures--perhaps our models will be wrong.

 

KUOW - Hike Minotaur Lake

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Updated Tuesday 9-11-2012

Hike is just east of Stevens Pass.

View of Minotaur and Labyrinth Mountain in background

Green Trails Maps- One of the 10 essentials
Check out Green Trails Maps for directions. Map for this week's trip is 144 . Click link below for complete list of maps.http:// http://greentrailsmaps.com/maps/index_Map_wa/
Photo below is on trail the way up
Photo below is view of the lake
Photo below is view from the top of Labyrinth Mountain of Glacier Peak
Photo below is view from the top of Labyrinth Mountain of Minotaur Lake
Driving directions: From Everett head east on US 2 for 65 miles to Stevens Pass. Continue east for another 4 miles. onto Smith Brook Road (Forest Road 6700). (From Leavenworth reach the turnoff in 30 miles.) Follow FR 6700 and go past Smithbrook trailhead and then past Nason Ridge Trailhead. At about 4 3/4 miles from Stevens there is a sharp left fork and take this and this is still FS 6700. Than at 6.8 miles from Stevens Pass turn left onto FR 6704. Proceed for 0.9 mile to the road's end and trailhead (elev. 3800 ft).
Trail stats: To lake only 1.60 miles and 1750 feet. That is steep!!! But worth it. Lake at 5500 feet. Top or Labyrinth is at 6376 a scramble.Bring map,compass and GPS as the directions are the best estimates that we have

KUOW Hike of the Week- Grand Park

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Updated Tuesday 9-18-2012
Grand Park Mt. Rainier National Park hike via short cutPhoto below view from the edge of Grand Park of Mt. Rainier
Green Trails Maps- One of the 10 essentials
Check out Green Trails Maps for directions. Map for this week's trip is 269S . Click link below for complete list of maps.http:// http://greentrailsmaps.com/maps/index_Map_wa/
Most of the photos below from Maria Lamarca Anderson

Photo below is Lake Eleanor
Photo below is Grand Park- 2 miles of meadows
Photo below is lunch break in the meadow
Photo below is Michael Fagin taking a nap
Photo below is Maria dancing in the meadow
Photo below is of meadow and Mt. Rainier
Driving directions: Drive state Route 410 about 24 miles east of Enumclaw and just past the viewpoint of Mount Rainier turn right onto Forest Service Road No. 73. Drive 10 miles to sign that says “Eleanor Creek.” There is not a trailhead sign but park on the right and you will see a boot path on the left. Walk a short distance and you will see sign that you have entered the National Park.Trail stats: 7 miles roundtrip and about 1500 foot elevation gain. You can go slightly further if you like.Please bring map-compass-GPS as these directions are our best estimates.
Check trails before you go, lots of trails closed due to fires. Biggest impact East Cascades.http:// http://inciweb.org/unit/closures/4984/ >