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While waiting to board my Alaska Airlines flight from Juneau to Seattle April 9, the all-to-common announcement came over the PA about a likely weather delay. As I happened to have my laptop handy with Internet access available, I quickly checked the Juneau airport weather observations. I did not see any weather issue that would keep the 737 on the ground. The ceiling and visibility were way above minimums. The wind was strong, but pretty well aligned with the runway…not too bad. Here are the observations in METAR format (click here for help in reading them).

PAJN 091353Z 12021G36KT 10SM -RA FEW018 BKN036 OVC050 06/02 A2918 RMK AO2
     PK WND 12036/1349 PRESFR SLP880 P0001 T00560022

PAJN 091453Z 13028G37KT 7SM -RA FEW013 BKN032 OVC045 05/03 A2914 RMK AO2 
     PK WND 13041/1431 SLP867 VIS LWR S-SW P0000 60004 T00500028 58048 

PAJN 091553Z 12022G33KT 3SM -RA FEW013 BKN032 OVC045 05/03 A2912 RMK AO2 
     PK WND 12036/1501 SLP859 P0004 T00500033

What was I missing? Before I could dig deeper, one of the pilots got on the PA and re-educated me, and the whole crowd–mostly seasoned Alaskan flyers with way more weather and aviation savvy than you’d find at a typical airport down south.

The problem was with wind, wind shear, and the resultant turbulence along the departure path rather than at the airport. There are not many options for departing Juneau ( a fact Juneau residents are acutely aware of), and with the full load we had, none that could bypass the areas of channeled winds coming out of the mountain valleys.

The surface chart shows the big picture. A strong low was making its way toward Yakutat, keeping off the coast, but ready to run its front over the panhandle. The map is for about 3 hours before the weather situation we were facing, so the front approaching the coast was probably right on our doorstep. The strong wind with a low like is made very turbulent as it passed between peaks, over ridges and accelerated down channels of the panhandle.

Surface chart for 12z 9 April 2013

A few years ago it would have taken a very careful look at many weather factors and a good amount of local knowledge to call this situation correctly and keep a plane from flying into the jaws of extreme turbulence, without grounding all flights. Now we have the JAWS of life for pilots and passengers: The Juneau Airport Wind System. This system uses an array of wind observations to predict the likelihood of moderate or severe turbulence as would be experienced by a Boeing 737 aircraft. Some of the wind obs are from the airport and surrounding ground-based anemometers, several from ridge and mountaintop anemometers, and a wealth of data streams in from three ground-based profilers, which detect the wind from the surface up through several thousand feet. Computer algorithms based on research aircraft flights flown in various weather situations grind out real time assessments of current turbulence conditions. Here’s what it looked like on the morning of April 9. [At the time I thought it a strong storm for April, but today, May 1 there is similar storm, somewhat weaker, but very vigorous for May, and with severe turbulence again flashing up on the JAWS page! Find the current conditions at http://pajk.arh.noaa.gov/jaws/jaws.php]

Juneau Airport Wind System screen capture for 15z 09 April 2013

Note the  “bottom line” block in the lower left showing any alerts: in this case four of the six areas had severe turbulence expected. The data on this page is well labeled, and there is much more info in the help page, and a good background of the system linked from the help page.

Shortly after our Alaska Airlines crew briefed us on various options, one of which involving lightening the load and using a different departure path, they said conditions had improved and they wanted to load up and take off as soon as possible. No doubt they had a constant eye on the JAWS data, and we climbed above the jagged peaks with only light turbulence. We will never know if the severe turbulence was there a short while earlier. I’m not volunteering to challenge this system. The research has already been done, and from what I know, done well. This is truly a valuable system and a wise investment by the government which has doubtless saved much inconvenience, discomfort and possibly lives.

There’s more. On the descent into Ketchikan, we endured quite a bit of turbulence, easily in the moderate range for much of the time. People applauded after we were safely on the ground. While Ketchikan does not have the mountains around it quite like Juneau, just the strength of the wind over the lower terrain was enough in this case. Here are the METAR obs surrounding the time. Note the 50 kt gusts from the roof of the FAA facility.

SPECI PAKT 091405Z 14022G35KT 6SM -RA BR OVC021 07/07 A2954 RMK AO2 PK WND
     13043/1354 ROOF WIND 12035G50KT P0000 $
PAKT 091453Z 14020G32KT 10SM BKN019 OVC024 07/07 A2949 RMK AO2 PK WND
     13043/1354 RAE09 PRESFR SLP986 ROOF WIND 12035G45KT P0000 60022
     T00670067 58025 $
PAKT 091553Z 14020G28KT 4SM -RA BR OVC021 08/07 A2949 RMK PK WND 13034/1524
     RAB36 SLP985 ROOF WIND 12035G50KT P0001 T00780067 $ VIA AUTODIAL

Here also is the morning balloon sounding from Annette Island, a short distance to the south. The 65 kt (33 m/s) winds matched the winds from the Juneau profilers, but at a much lower altitude!

balloon sounding for 12z 09 April 2013 at Annette Island, AK

Now after the concern for turbulence on coming out of Juneau, then hitting a lot if it (without any prior talk) going into Ketchikan, the crew made sure to warn newly-boarded passengers about turbulence on the continuing southbound takeoff. It was then quite smooth, of course. That’s the weather business for you.

Dry cold, wet cold?   no.

Winter cold and summer cold?  no. Bitterly cold vs extremely cold?  no. Calm vs windy cold? close.

All these would make good blog subjects, but what I’m thinking about today is domestic cold vs imported cold. Seriously.

I have a good recent example. (more…)

The question in the title came to me in an email, but for every email I get there are probably hundreds asking the same question in Glennallen. Sure, there are thousands more asking it about where they live, be it Fairbanks or Juneau or Orlando for that matter. But I want to look at what appears to be a unusually cold spot this winter, the capital of the Copper River Valley, population, after throwing in close neighbors Gulkana, Gakona, Copper Center, etc, of a 1,100 or so very tough Alaskans.

Let’s look at the weather depiction map from yesterday Morning, courtesy of the Alaska Aviation Weather Unit. A great example, as Gulkana (that’s where the weather station is located), labeled with its 4 letter code PAGK, was the colder than any station except Northway (PAOR)! It was 40 below (Fahrenheit or Celsius, take your pick), colder than Fairbanks at the time and most of the rest of those off the map to the north. Those around it are way warmer, with only Eureka (PAZK) being in the same ballpark. Talkeetna (PATK) and Anchorage (PANC) are not even below zero! Are not all these places in the Southcentral zone?

(more…)

When I moved to Alaska in 1982, I was a real cheechako. I did not even know what termination dust was. The term was never mentioned in meteorology school. It does not appear in the meteorology glossaries of the NWS, American Meteorological Society or the Weather Channel, nor is it in Wikipedia. Back then it was a bit of an initiation for new arrivals to figure out what the others were talking about. Here are a couple recent examples, taken Tuesday evening, August 28th. (I back-dated this post a few days to that date.)

Looking west from the Haines High School track. (more…)

The cold, cloudy, wet weather has been with Alaskans since May, with a only a few short breaks here and there. Here’s a recent example from the usually warmish Copper River Basin: A rainy day Wednesday in Glennallen (wx data from close-by Gulkana–that’s where the airport and weather station are for the Glennallen area) with a high of only 48F (9C), then some clearing overnight allowing the temperature to drop to 29F (-2C), the coldest spot in the state Thursday morning. That’s right, below freezing in late June.  And it’s the 6th day in a row that the cold spot of the state has been at or below zero Celsius. (more…)

After a particularly nasty winter, Alaskans usually hope for a nice summer to erase the memories. Actually, a lot of Alaskan’s do that after every winter.  Well, we are just finishing up (or still waiting for the end of, depending on what part of Alaska you live in)  a very tough winter in most parts of Alaska, so hope runs high for the summer. Will it soothe or disappoint the weather weary?

The truthful answer? I don’t know. Seasonal forecasts for the warm season have little skill in Alaska. Worse than winter forecasts, which are far from reliable.

There are two points pertinent to this issue:

1. Temperatures vary much less in summer than in winter. While that might make it easier by reducing the potential forecast error,  in reality the forecast needs to show skill within the context of that variability. This is the technical explanation. From a human standpoint these smaller temperature variations seem to be relatively more important in summer, perhaps because there is more outside activity. There is about as much grumbling about a 3 degree colder than normal summer month as there is about a 6 degree colder than normal winter month.
2. Correlations of summer weather in Alaska with climate systems such as the El Nino/La Nina are either too weak or as yet too poorly understood to be a very useful predictor of a particular summer. Frankly most people have been trying to figure the links with winter weather, probably because winter weather is seen as more important (dangerous, costly, etc.) and I suppose that is right to an extent.

So I’m not putting much confidence in my prediction, and asking you not to as well. This is more of a theory to be played out over the next 3 months than something to make decisions on. (more…)

If you have been waiting to see some statistics on how our winter of 2011-2012 rated compared to climate history, or if you were hoping for a long range forecast (educated guess) for the summer of 2012, stay tuned, I am working on both. I’ve been preoccupied with getting the 2013 Alaska Weather Calendar printed and out to stores. That rush is easing and I hope to increase the blogging frequency at least to where it was before. If you would like an automatic email when a new article is posted, sign up for that service under “Subscribe to Posts” either on the menu items across the top of the page or on the right hand sidebar items.

Of course, I can’t really do a winter wrap-up or declare a winner in the Iditasnow until winter is a little more over, can I? Look at what has been happening around the state:

In the Arctic, no one expects anything like spring weather for some time to come. In fact, the weather there has been pretty average for this time of year: Temperatures in the 20s F (around -5C) with some wind, a little snow and blowing snow lately. However, just a few days ago it was below zero on the North Slope and Bering Strait area. After a very snowy winter in Kotzebue, the 27 inches (69 cm) of snow on the ground is holding steady with well below freezing temperatures.

The plows are still needed in Shishmaref. Click on the image to see it full size.

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Since the leap day checkpoint report, most towns have slowed their snowfall pace. Haines and Yakutat, however, have been running hard, each having added an impressive 50 inches this first half of March.

The Top Ten as of 15 March

Remember, the standings are based on snowfall this season compared to the station’s average yearly snowfall. (No, I did not come up with this rating scheme to just to put Haines in the lead). (more…)