When I saw the high temperature for July 2nd was 83F, I knew that 80F days in Sitka were rare, but I didn’t realize just how unusual.

By the time July 31st reached an all time record-tying high of 88F, I had done some investigation and learned that it was only the third* time since 2005 that the temperature reached at least 80F at the airport, and only the 10th day in my lifetime.

In fact, going back 50 years, there are only 15 days that made the mark.

Over the years there have been two primary weather reporting stations, one at the airport started recording in 1944, and the Magnetic Observatory was in operation from 1899-1989. In 2005 one called Sitka 1 NE started up, and I believe it’s at (or at least quite close to) the old Magnetic Observatory station.

There are differences in temperatures between the two stations related in part to the moderating effects of the ocean. (The largest consistent differences in reported highs could be expected to occur on clear days, with warmer temperatures at the airport in winter, and cooler in the summer.)

With this in mind, I took a look at the data from all three stations, going back to 1970 (with a tabular summary by decade going back to 1899).

The Past 50 Years

2010s

Although summer 2019 was warm and dry (with a record tying streak without rain at the airport), it never reached 80F. Prior to this July (2020), the last time the official temperature was at least 80F (and the only time since 2005), was July 6th, 2009 when it hit 84F.

(I was out of town the days before, and suspect that I returned that evening or the next day, so missed out on the heat, as the high on the 7th was back to a more seasonable 62F.)

During the 11 year stretch between 80 degree temperatures at the airport, there were an additional two days that topped out at 80F at Sitka 1 NE, June 23rd, 2012 (only 69F at the airport, so perhaps there was a good sea breeze?), and June 15th, 2015 (with a high of 77F at the airport).

2000s

The first 80F temperatures of the millennium were recorded June 19-20th, 2004 when the highs were 81F.

I have a specific memory of the 20th. I remember the heat felt stifling while at a picnic at Halibut Point rec that afternoon. . In my memory, I was thinking this was the day had broke the all time record and hit 89F, but clearly this was incorrect. Looking deeper, I found this had blended with another hot day later in the summer**.

Only one other year since 1970 had produced two 80F degree days, but 2004 wasn’t done yet, as August was especially remarkable for heat.

On August 10th it was 83F, and August 15th, 2004 hit 82F (originally reported as 89F**). These were in the midst of 7 of 9 days that were at least 70F, and 11 of 12 that were at least 67F.

August 2004 ended up with what was easily the warmest three week stretch (in terms of daily high temperatures) ever recorded at the airport, with the high temperature averaging 69.9F. The next closest three week stretch took place in August 1977 and its average high was more than two degrees cooler at 67.5F***.

I am a little disappointed that I only have a few photos with captions (and no journals) from a handful of days that August, but the photos I do have feature sunny conditions.

With four 80 degree days, and the general heat in August, I’m wondering what the overall weather patterns were that summer that drove the warmth, as it seems like they must have been unusual.

On August 9th, 2005 the airport reported a high of 80F (the second day of 5 in a row where highs were at least 70F). This was just a week before the Sitka 1 NE data record starts. I was in town, but have no particular memory of this day (this was before I started trying to be more consistent with weblogs, and I did not take any pictures that day).

1980s-1990s

August 12th, 1990 hit 83F and was the only day between 1976 and 2004 to break 80F at the airport. (Between 1980 and 1999 there were a couple of days that reached 79F, and a handful that topped out at 78F).

The 1980s encompassed most of my childhood, and I feel like I remember at least a couple of (what seemed to me to be very hot days), with temperatures reported in the 80s. During this time, weather data was recorded at the Magnetic Observatory (through 1989), which I believe may have been considered the official Sitka weather record at the time.

There were three days that broke 80F at the Magnetic Observatory. June 29th, 1985 was 80F (75F reported at the airport), and two days in 1980. June 5th was 86F, and August 11th, 83F.

The summer of 1980 is when I turned 5, and I’m pretty sure at least one of those days (or perhaps a blend of both) is in my memory, in the hazy sort of way that memories from early childhood sometimes are. I remember being outside in the sun, in shorts and a tank top, feeling the heat was unbearable. Attached to this memory is the recollection that the temperature had been in the 80s (84F is what stuck with me over the years).

1970s

The early part of the 1970s more regularly saw 80F degree days at the airport, with one each in 1970, 1971, 1972 and two each in 1975 and 1976 (including the just tied record of 88F on July 30th, 1976). Additionally, there was an 80F day at the Magnetic Observatory in 1974.

(It’s a little difficult to directly compare daily records between the airport and the Magnetic Observatory during this time period, the data was collected differently at each location, with airport records apparently for the calendar day, and the Magnetic Observatory daily recordings documenting the 24 hour period ending at 3pm.)

Other Notes and Questions

What does it take to get to 80F in Sitka?
Given the rarity of 80F days at Sitka overall, it’s clear the circumstances required to produce such heat are relatively unusual. I have some sense that it might depend on warm air aloft, perhaps some downsloping air movement (though it’s not clear to me how much affect that might have in Sitka), and something to prevent a sea breeze from forming and bringing in air cooled by the waters of Sitka Sound and the Gulf of Alaska. (If anyone reading this can explain what sorts of factors can result in the hottest days here, I would love to learn more!)

1970-1976 and a shift in the PDO index
In 1976 there was a shift in the Pacific Decadal Oscillation index which resulted in generally warmer temperatures throughout Alaska (though less pronounced in the summer). It’s interesting to me that in the seven years immediately preceding the shift (1970-1976) there were six days of 80F at the airport, and in the following 27 years (1977-2003) there was only one, despite a warmer baseline. Is there something associated with the PDO that makes more extreme temperatures less likely to occur despite warmer conditions overall?

Clustering of 80F days, patterns or randomness?
That said, the 1970-1976 period was unusual. Over the 70+ years of the airport records, there are a couple of other clusters of years (1950-1952; 2004-2005) where at least five 80F days were recorded, but these were driven by unusual years (two days in 1950, three in 1952; four days in 2004).

At the time, five days of at least 80F over two summers in 2004-2005 might have suggested the possibility of more regularly occurring hot days. Fifteen years on, and with the benefit of a look through the longer record, they were clearly one of a handful of clusters in the record.

80F is a nice round number (in our base-10 counting system, at least!), but ultimately an arbitrary one. It does seem to be an interesting cut-off for Sitka, but may be less so for other communities in the region (which may have a bit less influence from the cool waters of the Gulf of Alaska).

By their nature, the extreme values of data sets tend to be highly variable/noisy, with clusters that may be essentially random (but still invite our pattern-seeking minds to seek an explanation). At some point in the future, I may look at nearby temperature cutoffs, and see if things look much different (at least qualitatively).

While acknowledging the clustering could be the result of basically random processes, I wonder if there could be climatic conditions that show up on a scale of months or years which might be a factor that increases (or significantly decreases) the possibility of temperatures reaching 80F.

Differences in temperatures between nearby stations?
I’m interested by how different the reported high temperatures at different stations on some of the days. A few degrees seems pretty reasonable, but in some cases, the difference is 10-15F – I am guessing it has something to do with a marine stratus layer or sea breeze affecting the airport, but I’m not sure. Perhaps at some point I’ll investigate the temperature differences more systematically to see how much the difference varies overall.

What’s your experience with 80F in Sitka?
If you are reading this and have memories of 80F days in Sitka, please leave a comment! What do you remember about some of the hottest days in Sitka’s recorded history?

Data Sources

NOAA Regional Climate Centers xmACIS2 site – has data from all three stations used in this post.

NOAA Online Weather Data (Juneau Office of NWS) – only shows records from the airport

Zoom.earth – satellite imagery from July 31st

Notes

*The weather records show July 21-22nd, 2017 with highs of 86F at the airport. I’m quite positive these are erroneous, as the pictures I have for that day show cloudy conditions, and the Sitka 1 NE station shows highs in the lower 60s. I have emailed the folks at the weather office in Juneau about this, and will update if I learn more.

** In the August 16th, 2004 edition of the Sitka Sentinel, the official high for the 15th was reported to be 89F, breaking the all-time record of 88F, set July 30th, 1976. So apparently my memory did some blending. It may be that I came to associate my memory of the record hot weather picnic with the picture taken on June 20th. Another possibility is the picnic did take place on the 20th, but I later attached the reported record heat to that day mistakenly.

*** The Magnetic Observatory did have a three week stretch that averaged 71F in August 1923, which included 6 days in a row that reached at least 77F, with four of them hitting 80F.

While there is no way to know what 2004’s 69.9F stretch would have looked like at the Magnetic Obsrvatory, the 1977 three week period where highs averaged 67.5F at the airport is directly comparable with that period averaging 69.1F at the Magnetic Observatory. This 1.6F difference suggests 2004 was plausibly just as hot, and possibly even slightly hotter than the three weeks in August 1923.

Tables

Table of 80F day counts by Station and Month

I enjoyed looking through recent satellite photos this evening and included three with this post.

The first shows the situation as the high pressure was getting well established on Sunday. Clear skies over southeast and some clouds milling about offshore. In the second on, from Monday, the clouds are offshore and arrayed in distinct lines, which I believe is due to the strong winds blowing out. That pattern persisted into today, perhaps even growing stronger, as seen in the third photo.

Part 2: During which month of the year is Sitka least likely to have a day without precipitation? Most likely? (note, this isn’t necessarily the same as the wettest and driest months – as those are based on total precipitation that falls in a month)

Feel free to leave your guesses in the comments, if you like.

I’ll post the answers (at least based on the past 10 years) sometime in the next few days.

I was a little surprised to find that I had to go all the way back to May to find 2 clear days in a row, and the last time we had three was February. Including mostly sunny days was a little better, but the last time we had 3 or more Clear/Mostly Sunny days in a row was still last May. Of course I’ve never really looked at how many days in a row of Clear/Mostly Sunny skies are typical in any given month, so I didn’t really know if this was typical or not, so I looked back a bit further.

In the end I included 10 years of data 2002-2011. For each month I checked the number of clear days, the number of mostly sunny days, the longest run of Clear days, and the longest run of Clear/Mostly Sunny days. There were some problems with this method, as it’s not entirely clear how Weather Underground decides how to rate a given day. Looking at the daily summaries I saw for each observation (typically at least one an hour, each day), there was an entry for “conditions” which included Clear, Mostly Sunny, Mostly Cloudy, Overcast, etc. It would be better to get that data and do the summarizing myself, according to what I’m interested in, but that will be a much more involved project (which I may get to at some point).

I found that 2011 was one of the least sunny in the last decade. There were only 19 clear days in 2011 (7 of which were in January, with an addition 4 each in February and March). 2008 was second with 20 and 2007 had 21. With mostly sunny days included, 2011 had 56 total – second to 2007’s 49. 2008 had 59. When January is dropped, 2011 falls below 2007 45 to 47.

Of course as often happens, I wandered through the data looking at various other comparisons and summaries. I’m planning to write a follow up post with some supporting plots in the coming days.

It’s interesting to me that I didn’t perceive 2011 to be a particularly gloomy year. I’m not entirely sure why that is the case. I imagine part of it is that I’m used to cloudy weather, so I don’t make particular note of it, even if there’s more than usual. (On the other hand, months/years with more than typical sun do tend to stand out more.) It could also be due in part to how Weather Underground was summarizing the condition reports into a single condition for the entire. For example, a day where a little rain fell at 2am, but it was clear by 8am and remained clear throughout the day would probably show up as a day with rain – even though my experience of it would have been as a sunny day. It will be interesting to see how the general results I’ve found here compare to a more careful analysis with the daily summary data (if/when I ever get that done).

The other primary pattern is associated with low pressure systems moving across the North Pacific. Filled with moisture picked up from the relatively warm (for this time of year) oceans, some systems pull up warmer air and additional moisture and from near Hawaii (the so-called “Pineapple Express”) resulting in warmer temperatures and rain, while others manage to pull in some cooler air from the north and temperatures stay near freezing with snow a distinct possibility. These low pressure systems often bring thick cloud cover, and combined with the low angle of the sun and typical lack of snow, days can go by without the level of brightness climbing above gloomy dusk. For people who experience mood troubles in winter around here, I suspect these days of gloom have as much to do with it as the overall shortness of daylight hours.

Yesterday provided a nice contrast between these two patterns. Much of the day skies were mostly clear and sunshine brightened things up. By the time I headed out to take care of some grading at UAS, low clouds had started to move in but I could still see sunlight reflected off the Sisters. Shortly thereafter, the unnamed peak behind the Sisters was still in sunlight, but the Sisters themselves were no longer bright. I hurried down to Crescent Harbor, knowing I would have a less obstructed view of the mountains, and the contrast I found there struck me.

Looking back toward the high point on the island (see photo at top of this entry) – looking back at the mountains, it’s easy to imagine the sun has just dropped below the horizon from the perspective at sea level, with the last rays illuminating the snow covered peaks before the sunlight fades and the stars can be seen again.

Turning around and looking toward the ocean, it’s a different story. Heavy gray clouds filter the sunlight to the point where it seems as though the sun had already set, though that would not happen for another 20 minutes or more. Light snow consisting of small flakes reduces visibility even further but without the excitement that can come with large fluffy flakes drifting lazily down from the sky.

I found the contrast of moods between the two directions striking, and while I don’t actually mind the gloomy winter weather, I couldn’t help but find myself imagining being up on the sunlit peaks above the clouds, basking in the brightness, even if it wasn’t accompanied by much warmth.

Cumulus cloud expanding behind slope of Bear Mountain.

It’s been quite warm (by Sitka standards) over the past few days. Thursday’s high temperature of 75F broke the former record high for the date of 68F, set in 1990. It was slightly cooler on Friday, and the high temperature of 70F recorded at the airport did not come particularly close to breaking the record of 77F set in 1964, though several other communities (including Port Alexander on South Baranof island) did set records for the day.

The forecast for Friday called for clouds developing in the afternoon with a chance of thundershowers. I watched for cumulus clouds developing as the day went on, and although a few did, they seemed to stall out or dissipate rather quickly. The one shown in the photograph at the top of this post had mostly been blown apart (or so it seemed) within 20 minutes of the time I took the picture.

Graupel is a type of snow that forms when snow flakes fall through parts of the atmosphere that have supercooled water droplets. Instead of maintaining the form of flat snow flakes and/or elongated snow crystals, the supercooled water condenses as a rime on the surface that results in a pellet shape. Superficially, graupel looks a bit like hail, and many people call it that, but hail is a solid ball of ice that forms in repeated freezing/thawing cycles as water/ice is subject to updrafts and downdrafts in thunderstorms. With a little extra attention, it’s not hard to identify graupel from its less solid feel and slightly fuzzy appearance.

In Sitka, graupel is a fairly common form of precipitation from at least late fall through spring. I remember as a kid noticing that it seemed to fall, sometimes quite heavily, and then shortly after, a more traditional snow would begin. At this point, I’m not sure how strong that relationship is, but it did hold this week. We had a fair amount of graupel Saturday, especially in the afternoon and evening, with snow developing later in the evening and falling through much of the night. Perhaps the conditions that prevail as a front moves through are conducive to graupel formation, with snow falling after the passage of the front.

After nearly two months that seemed unseasonably warm and lacking in precipitation, this week has been a return to what I tend to expect of late winter and early spring weather. Monday’s cooler temperatures with heavy clouds and rain, were followed by a short reprieve in partly-cloudy Tuesday, but Wednesday temperatures dropped again, and we saw rain, snow, sleet, and maybe even a bit of hail broken up by brief patches of blue sky and attending sun.

The first report of a large flock in town was Friday morning, April 24. A commercial fisherman noted a flock of over 200 geese at the Turnaround and reported it to the Sitka Birds e-mail list. Over the days that followed, there were several more reports from the Turnaround, Totem Park and Starrigavan.

A conversation with Paul Norwood about some observations he made on a recent kayak trip south of town provided a suggestion as to why they showed up like. He mentioned seeing 2000 geese flying north over Biorka Island on Thursday, April 23. He said there was a light Northwest wind at the time, but it strengthened throughout the day, and later there were many smaller flocks flying back from the north in toward land.

Marge Ward and Marlys Tedin said there had been a similar abundance of Greater White-fronted Geese around town in 2002. Thanks to their detailed records, I was able to find the first large flocks were reported on the morning of May first at Swan Lake. A quick check of the weather history revealed there had been a strong Northwest wind blowing most of the previous day.

Given the weather immediately preceding the arrival of geese in 2002 and again this year, a strong Northwest winds provides a plausible explanation for the goose invasion. However, it is not yet clear whether there were other years when the Northwest wind blew during migration and geese did not show up in town. Maybe the cold winter and early spring also played a role. With snow and ice still persisting on even lower elevation lakes, perhaps locations the geese might ordinarily prefer were not available. Or, perhaps the typical migration route for these geese takes them up Chatham Straight or further east along the mainland. It would be interesting to know if large flocks of geese move up the outer coast, flying across the mouth of Sitka Sound most years, only moving into town in years when unfavorable winds push them back.

At around 1am, the temperature at the house was 54, though I noticed it was only 48 according to the local weather reading (at the airport). Typically it is cooler at the house (and it had been earlier in the day). Over the next 20 minutes or so, the temperature dropped down to 48 at the house as well. I went outside to take a look and saw the stars. I am guessing the break in the clouds moved in from the west, with temperatures to dropping as it went.

Recently I found out that Google Earth has added the ability view weather satellite imagery as a layer. Although I have found the satellite imagery for the northern Gulf of Alaska and Alaska before, looking at things on Google Earth makes it much easier to see the big picture as well as what is going on regionally.

For example, in the photo at the top of this post, notice the band of clouds stretching from near the equator all the way up into Southeast Alaska. The weather at this time was warm for the time of year, temperatures were in the low-to-mid 40s, and it was rainy. Looking at the weather pattern at the time, it seems likely this was due to warm air moving up from lower latitudes, cooling as it moved north, but still resulting in relatively warm temperatures.

Compare that to the current situation with clear skies and winds out of the north. Today’s satellite imagery shows the clear conditions prevailing over southeast and to the north. If you watch the 24-hour sequence of images (also available on Google Earth by clicking on the Weather > information layer), you can also see the clouds in motion.

It’s a fun thing to play with, and I suspect it will help my understanding of the regional weather as I compare what I see there with what I experience locally.