Friday, October 24, 2014

An Update on Windy Weekend and Hurricane Ana

The Inland Northwest will see some interesting weather over the next 4 days.  First, we have a strong Pacific storm moving through the area this weekend, then the potential for remnants of Hurricane Ana.  First, let's update the forecast for the weekend wind.

The satellite shows a beautiful storm off the West Coast.  The warm front of this storm is the cloud band stretching from Washington into Montana.  The cold front is the cloud band that extends from western Washington southward off the California coast.  The warm front is bringing us rain this evening.  It will lift northward into BC.  Then we'll have a dry start to Saturday, before the cold front brings more rain Saturday afternoon/evening. 

Infrared Satellite at 730pm PDT 24 Oct 2014
Here's the UW WRF forecast of wind gusts as the low approaches the coast.

The dark blue colors along the southern Oregon coast are gusts around 60 kts (70 mph).  There's already a high wind warning out for that area.

As the low moves onshore and eastward across the US/Canadian border, winds will increase Saturday night over the Inland Northwest.  The cold front should move over the Cascades around midnight, and reach the Panhandle before sunrise.  That's when the winds will be strongest.  Below is the forecast for 5 am Sunday:

The green shading in southeast Washington is 35 kts (40 mph).  There's a bulls-eye of 60 kts over the Blue Mountains.

But this computer forecast looks too conservative.  The pattern of a deep low passing just to our north is a common pattern for high winds here.  Actually, the perfect pattern for really strong winds is where the low tracks just a little farther to the north.

So for the area from Spokane/Cd'A down to Lewiston and over to Tri Cities, expect wind gusts to 50 mph Saturday night into Sunday morning.

Then our attention turns to Hurricane Ana, churning northwest of Hawaii.

IR Satellite image 830pm PDT 25 Oct 2014

Here's the GFS forecast Friday evening.  The little white circle with the yellow shading is Ana.

GFS forecast of SLP (white lines) and precipitation (shading) for 11pm 25 Oct 2014

By Saturday afternoon, the Pacific low has picked up Ana and is moving her remnants to the north.

GFS forecast of SLP (white lines) and precipitation (shading) for 5pm 26 Oct 2014
24 hours later, the low is moving into the Gulf of Alaska towards the Canadian coast.

GFS forecast of SLP (white lines) and precipitation (shading) for 5pm 27 Oct 2014
And finally by Tuesday morning, the rain has reached the Inland Northwest.

GFS forecast of SLP (white lines) and precipitation (shading) for 5am 28 Oct 2014
Here's the track forecast from the Central Pacific Hurricane Center in Hawaii:

We can't remember ever seeing a situation quite like this.

So on Tuesday morning, as the rain falls on your windshield as you drive to work, you can thank Hurricane Ana for providing some of the moisture to the Inland Northwest.  

Once again, by the time this reaches the Pacific Northwest, it will not be a tropical storm, just the moisture remnants of it.  Still, it's kinda neat to think that our rain came in part from a Hurricane.

Thursday, October 23, 2014

A windy weekend expected

In yesterday's blog post, we talked about the potential for the remnants of Tropical Storm Ana to head to the Inland Northwest early next week.  In that blog, we briefly mentioned a possible wind storm on the weekend, before Ana arrives.  Let's take a look at some details of this event.

First, we'll look at the overall set up.  Here's the GFS model forecast for rain (shading) and sea-level pressure (red lines).

The forecast shows a deep low pressure center off the West coast Friday afternoon.  The precipitation extending across northern Oregon into central Idaho is associated with the warm front that will move into our area.  By this time, strong winds will be developing along the southern Oregon coast.

Overnight, the low deepens and moves north.  Here's the forecast for Saturday morning.

GFS Forecast SLP (red contours) and precipitation (shading) for Saturday morning 25 Oct
Now the low pressure is down to 990mb, and impressive low.  The warm front has lifted up to the WA/BC border.  The tightly packed pressure lines (red contours) indicate wind strength.  The tighter the packing, the stronger the winds.  Over the Inland Northwest, winds will be from the east on Saturday, blowing into the low.  Along the Oregon Coast it will be extremely windy.

By Saturday afternoon (below), the low moves onto the Olympic Peninsula and fills to 995mb.  

GFS Forecast SLP (red contours) and precipitation (shading) for Saturday afternoon 25 Oct

And by Sunday morning, the low will be in southeast British Columbia.

GFS Forecast SLP (red contours) and precipitation (shading) for Sunday 26 Oct

It's this Saturday night and Sunday morning period where the winds could be rather strong across the Inland Northwest.  On the one hand, the pattern for this storm is one that is common for strong winds, with the low moving by just to the north of the US/Canadian border.  On the down side, it's moving through at night, which tends to inhibit winds somewhat.  But in this case, that probably won't matter.

Now let's look a bit closer at the details.  First, here's the University of Washington WRF model forecast for Saturday.

This shows forecast gusts of 70+ mph along the central Oregon coast.  Not good beach umbrella weather.

And here's the WRF forecast for wind gusts Saturday evening:

The area of red and orange in southeast Washington is a forecast of up to 57 kts, or 65 mph.  Now, before you say "glad I don't live in southeast Washington", this is just one model forecast.  The next model run (tonight) could move that area of strong winds to a slightly different area, such as Tri Cities, or Pullman, or Spokane.  At this point, it's too early to tell exactly where the strongest winds will occur, and just how strong they'll be.

As for Tropical Storm Ana, the GFS and ECMWF models are still showing solutions similar to yesterday's blog.  Here's the GFS forecast for Tuesday afternoon:

GFS Forecast SLP (red contours) and precipitation (shading) for Tuesday 29 Oct
We'll write more about this Friday evening.

Wednesday, October 22, 2014

A Tropical Storm for the Inland Northwest?

In the past we've mentioned how much of the moisture that falls on our heads in the Inland Northwest actually traces it's origins back to the tropics.  The rain that is currently falling on the Northwest US is actually a perfect example of this.  The image below shows a global view of atmospheric moisture. 

Global Precipitable Water - 22 Oct 2014

The red/orange colors show the highest moisture is located in the tropics.  But there are lines of moisture (yellow and light blue colors) that extend away from the tropics in both hemispheres.  These are now being called Atmospheric Rivers.  Storms moving across the globe in the mid-latitudes "tap" into the tropical moisture and bring it poleward.  This is all a part of the global atmospheric circulation.  The current imagery shows that the moisture hitting the West Coast of the U.S. is an east-west "river" of moisture that originated in the central Pacific tropics.

But there's a more subtle feature hidden in these images that may impact our weather early next week.  If you look near the Hawaiian Islands (center of the image), you'll see a swirl of orange.  This is Tropical Storm Ana.  She passed just south of the Big Island late last week and it now west of the Islands.

There's a large storm further to the west (look at the large swirl east of Japan).  The computer forecast models expect this storm to merge with Ana as it moves eastward across the Pacific.  Where will it go?

The GFS model has an interesting forecast.  First, here's the weather in the Pacific on Wednesday afternoon.

GFS forecast of Sea Level Pressure (contours) and Precipitation (shading) Wed 22 Oct 2014

You can clearly see Tropical Storm Ana, as well as the Pacific Storm that we referred to in the previous satellite image.  Also you can see the large area of rain that will impact the Northwest Wednesday and Thursday.

By Saturday (image below), the Pacific storm is starting to pull the remnants of Ana to the north.  Meanwhile, a rather strong storm is forecast to hit the Pacific Northwest for the weekend.  The Washington and Oregon coasts will see strong winds with this storm Friday night.  By Saturday night and Sunday, the strong winds will move into the Inland Northwest, so be ready for that.

GFS forecast of Sea Level Pressure (contours) and Precipitation (shading) Sat 25 Oct 2014

For early next week, the GFS has the remnants of Ana moving into the Pac NW.  

GFS forecast of Sea Level Pressure (contours) and Precipitation (shading) Tue 28 Oct 2014
Let's be clear.  This is just one model forecast, and it's still 7 days away.  And even if it comes to pass, this will not be a Tropical Storm by this point.  It is merely the remnants of Ana.  Even so, it could still be a very wet and windy storm.

Here's another model forecast.  This image show the forecast moisture.  The black arrows represent the movement of the moisture.  It's a nice depiction of the potential from this storm.  The first image is the forecast for Saturday. It shows the moisture from Ana merging with the Pacific storm on the left side of the image.

GFS Integrated Vapor Transport Forecast for Saturday 25 Oct 2014

And by the middle of next week, there's a lot of moisture heading for the West Coast.
GFS Integrated Vapor Transport Forecast for Wed 29 Oct 2014

However, as mentioned, the GFS is just one forecast model.  Here's the ECMWF model forecast for this storm Sunday.  The Pacific storm is entering the Gulf of Alaska, with the remnants of Ana to it's south.

But by next week, the ECMWF has the low much farther north, impacting the west coast of British Columbia.  We could still see some rain from this forecast, but not as much as what the GFS is forecasting.

So as usual, stay tuned to the forecasts.  As this situation evolves, we'll try to update this blog to give you a better idea of what to expect.

Tuesday, September 23, 2014

2014 Open House

Saturday September 20th was a Glorious Weather Day as the National Weather Service in Spokane held our 5th Open House event hosting the general public at our facility in Airway Heights. Around 300 guests visited between 10 am and 4 pm and were treated to a number of displays, presentations, events and fun activities.

The Open House was truly that, allowing the guests to roam freely thru most of facility. Staff were on hand in all areas to meet, greet, conduct demonstrations and answer questions. Informative displays explained many of the issues and subjects the NWS deals with on a daily basis. A tented area allowed for added space for more displays and a presentation mini-theater.

Upon entering the front door guests were greeted by Admin Assistant Rose Tibbitts who asked guests to sign in and then explained the overall set up and general flow of the event.

The conference room was turned into a display area with posters, pictures, a presentation on the 2014 wild summer weather and a weather quiz. Do you know the hottest temperature ever recorded in Washington?

The Operations Area was set up so that the normal forecast and observation functions could continue uninterrupted, while guests could interact with a forecaster at an AWIPS workstation. Forecaster Steve Bodnar manned the AWIPS workstation for most of the day explaining how we formulate and issue our forecasts and warnings.

Guests then walked into the Electronics Shop where Electronics Systems Analyst Dwight Williams explained the various system he and the El Techs maintain and repair. Displays on the Doppler Radar, ASOS, NOAA Weather Radio and the Cooperative Observation Program were featured in this area. 

Then it was outside to the tented area for some special displays and events! The Kids Activity Area is always a big hit at our Open House Events. The kids could conduct the Rain Gauge Experiment, see the Cloud-in-a-Bottle, make a Wind Sock, Learn about Lightning Safety and more! Forecasters Robin Fox and Laurie Nisbet lent their tireless energy to this active part of the tour.

Service Hydrologist Katherine Rowden staffed the Hydrology Table again, giving demonstrations with the large Flood Plain Model. Adjusting the flow from the 2011 Open House, the demonstration was done at set times allowing Katherine to stay relatively dry. She also had information on the office Hydrology Program and the recent Burn Area Emergency Response team work she participated in for the Carlton Complex Fire.

Speaking of Fire, Incident Meteorologists Jon Fox and Todd Carter donned their Nomex clothing and staffed the Fire Weather table. They had videos, handouts and a wealth of knowledge on how we become part of the Incident Management Teams that manage wild land fires.

Also in the tented area was a mini-theater were presentations were done. Scheduled at various times during the day subjects included "The NWS, Who We Are and What We Do", "Volunteer Observers" and "The Winter Outlook". Science Officer Ron Miller lent his expertise to the presentation on what we expect for this upcoming El Nino winter. 

A Special Presentation was done just before noon as Meteorologist in Charge John Livingston presented Nancy Taylor of Lacrosse WA with the Thomas Jefferson Award. Mrs. Taylor is a Cooperative Observer, taking a once-a-day observation of temperature, rainfall and snowfall. She received the award for her years of dedicated service. This is the highest award given by the NWS Cooperative Observer Program and one of five given across the nation in 2014.

The Event concluded with the 4 PM Weather Balloon Launch. Always a popular part of the day, Observations Program Leader Mark Turner gave folks an idea of why we still release weather balloons with instruments attached, how far they go, where they end up, and then answering all the other questions that people ask about this program.

Thanks to all who came out to our 2014 Open House and if you missed it, look for announcements for our 2016 Event in about 2 years!


Friday, September 19, 2014

Was this the hottest summer ever?

Some of you may have heard that this was the hottest summer ever in the Inland Northwest.  This strong statement may have been inferred from the statistics put out by the National Weather Service office in Spokane.  So let's take a look and see if this is true.

First, we need to define summer.  The calendar says that summer is from June 21st to September 21st.  But this is astronomical summer, which is defined as the longest day to the autumnal equinox.  This doesn't have anything to do with summer.  Another definition is meteorological summer, which is just the 3 months of June, July and August.  But if you've lived in the Inland Northwest for awhile, you know that June is most definitely not a summer month.  It can have glimpses of summer, but consistent warmth is rare.  So we typically define summer as Independence Day to Labor Day, or more simple, July and August.  Yes, that's right, there's only about 2 true months of summer in our corner of the world.

So now let's look at the numbers. Here's the average temperature for July and August.

Average Temp
73.5°F (1998)
78.5°F (1939)
77.6°F (2004)

Sure looks like 2014 was indeed the hottest summer ever.  But before we pass judgement, lets look at another measure of summer.  We typically track the number of days that reach 90°F or hotter.  Why?  Because one really cool day can offset 3 hot days when you average them together.  Counting 90°F days measures how many days were truly hot, regardless of how cool the other days were.  So here's the numbers:

Number of 90+F Days
39 (1958)
80 (1938)
56 (1970)

These numbers seem to tell a different story.  Yes, there were more 90+°F days than normal, but they are far from the record levels.  In fact, in all 3 cities, the number of 90+°F days in 2014 is actually less than 2013.

So which is right?  Was it a record hot summer, or just a bit hotter than normal?  The answer lies in the definition and calculation of "Average" temperature.  The average temperature is an average of both the max and min temperature.  So lets see the numbers for the max and min separately.

Average Max Temp
87.2°F (tied 5th)
93.6°F (13th)
90.6°F (13th)
88.5°F (1998)
96.1°F (1939)
92.5°F (1971)

Average Min Temp
60.8°F (1st)
63.4°F (1st)
64.3°F (tied 2nd)
59.6°F (2013)
62.7°F (1990)
64.4°F (2004)

There's a lot of numbers here.  The thing to notice is that for the Max Temperatures, this summer wasn't the hottest.  It was hot, well above normal, but not the hottest ever.  But when you look at the Min Temperatures, you find out that this was the warmest summer ever for Spokane and Lewiston, and the 2nd warmest for Wenatchee.  What gives?  Why were the Min Temperatures so warm this summer?

Turns out, it's not just this summer.  Let's look at the warmest Min Temperatures for Spokane in July and August.

Min Temp

Again, a lot of numbers to digest.  Notice anything unusual?  Of the 15 warmest Min Temperatures for July and August, 12 of them have occurred since 1998.  Are the summer nights really getting warmer?

One way to check this is to look at other nearby sites that are more remote.  There is a long historical record of weather observations from the Priest River Experimental Forest.  As the name implies, these are taken in a forest, far from any urban influence.    Rather than bore you with even more numbers, I'll just tell you that of the top 15 warmest Min Temps July/August at Priest River, only 2 of them are since 1998.  Some are from the 1970s, some from the 1940s.  The warmest is from 1905.  In other words, they are more random, as you would expect.

So why are Spokane summer nights so warm?  The answer is the location of the temperature sensor.  

The official NWS ASOS sensor is located in the middle of Spokane Airport.  It was placed there in 1995.  Notice all the concrete around there?  The sensor is surrounded by it.  That pavement absorbs the sun's warmth during the day, and then releases it at night.  The official sensor has been at the airport since 1947, but the airport continues to grow.  The previous location for the thermometer was north of the current parking lots, away from much of the effects of the runways.

Additionally, the late night wind at the Spokane Airport is often from the northeast during the summer.  Where is that air coming from?

That's right, the city of Spokane lies to the northeast of the airport.  So all of the urban warmth is warming the air that moves over the airport during the night.

Professor Cliff Mass has a similar analysis of the SeaTac temperatures in his blog:

So what was the cause of our hot summer, and how extensive was it?  First, let's look at the state-based ranking of temperatures for July and August.  Here's July:

The number represents the historical ranking.  Since there are 120 years in this database, the 116 for Washington as well as Idaho means that this was the 5th warmest July in the last 120 years.  Again, this uses the Average Temperature.  Parts of the central US had their coldest July ever.

As we've pointed out, August cooled down a bit.  But even so, for Washington, it was still the 7th warmest statewide.  Take a look at the other parts of the West.  Utah had it's 8th warmest July ever, but it's 15th coldest August.

For June through August, the largest anomaly was along the West Coast, although it was still above normal over much of the western US.

So what was the cause of this anomalous warmth?  Meteorologists actually pay more attention to the layers of the atmosphere well above the surface.  And the anomaly chart at 20,000 feet does a nice job of showing the cause of our heat:
500mb Height anomaly for July 1 - August 15, 2014

The "warm" colors are areas where the pressure was stronger than normal.  As you can see for the US, the largest anomaly existed over the Northwest, while a low pressure anomaly prevailed over the northeast US (they didn't have a warm summer). We usually have high pressure over the West during the summer, but this year, it was extra-strong.

The weather pattern actually shifted in mid-August.  Our weather responded by being more normal for the latter half of August.  Here's that same anomaly chart for August 16th through the 31st:
500mb Height anomaly Aug 16-31, 2014

Notice how the entire pattern has shifted.  The strong positive anomaly is now over the Gulf of Alaska, with a negative anomaly over much of the West.

So what will happen this winter?  We'll address that in an upcoming blog.