| April 2012 - |
The Climate of Alaska for 2011
Gerd
Wendler, Blake Moore and Kevin Galloway
Alaska
Climate Research Center, Geophysical Institute, UAF
This review of the climate of Alaska is predominantly based on
the 20 first order climatological stations in Alaska, which are operated by
NOAAÕs National Weather Service. These stations are all of high quality,
operated by professional meteorologists with identical or similar
meteorological instrumentation and observational practices. However, this
should not be taken as a sign that stations, which might be operated by other
agencies, industries or private individuals are of poor quality. We mention new
record values of these latter stations in the monthly summaries.
Temperature
The mean average annual temperature in 2011 for the 20 stations
was 32.5¡F, a small negative departure of 0.4¡F from the 30-year normal of
32.9¡F. It
should be pointed out, that we used the normal from the time period 1981-2010
to determine the departure from the mean. NOAAÕs National Climate Data Center
(NCDC), advised that for the months January – July, the old normals of
1971-2000 should be used, as the new normals were not calculated and quality
controlled at the beginning of the year. During the middle of the year, they
became available, and they were used since August 2011. For our monthly
reviews, we followed their advice. Hence, when looking at the table in this
write-up for a specific month and a specific station, you might find slight
differences in the deviations reported in the monthly reports for the first 7
months of the year. All the new normals can be obtained from NCDC at:
http://ggweather.com/normals/AK.html.
For
2011, there were only 4 stations with a positive deviation, Barrow in Northern
Alaska having the highest value with +2.2¡F, continuing the trend of
substantial warming observed on the North Slope over the last decades (Wendler,
Shulski and Moore 2009). The other extreme was found in Homer, on the Kenai Peninsula, which recorded
the highest negative deviation with -2.4¡F. Altogether, the deviations from the
mean were rather modest. In Figure 1 we analyzed the data, and it can be
seen that northwestern Alaska was above normal,
Figure1:
Isoplete presentation of the temperatures deviations from the normal
(1981-2010) for 2011 based on all Alaskan 1st order meteorological
stations.
while
southern Alaska was below normal with the exception of Yakutat, which reported
the exact climatic normal value. Actual temperature deviations by station can
be seen from Table A. 15 of the 20 stations gave negative values with a mean
negative deviation of -0.9¡F, the mean value of the 4 positive deviation being
+1.1¡F.
|
Station
|
Temperature
|
|
Observed
(¡F)
|
Normal
(¡F)
|
Delta
(¡F)
|
|
Anchorage
|
36.7
|
37.1
|
-0.4
|
|
Annette
|
45.0
|
46.6
|
-1.6
|
|
Barrow
|
14.0
|
11.8
|
2.2
|
|
Bethel
|
29.5
|
30.7
|
-1.2
|
|
Bettles
|
23.0
|
23.5
|
-0.5
|
|
Big Delta
|
28.6
|
29.0
|
-0.4
|
|
Cold Bay
|
38.6
|
38.8
|
-0.2
|
|
Fairbanks
|
27.7
|
27.7
|
0.0
|
|
Gulkana
|
27.8
|
28.2
|
-0.4
|
|
Homer
|
36.3
|
38.7
|
-2.4
|
|
Juneau
|
40.6
|
42.1
|
-1.5
|
|
King Salmon
|
34.1
|
35.2
|
-1.1
|
|
Kodiak
|
40.5
|
40.9
|
-0.4
|
|
Kotzebue
|
24.1
|
22.9
|
1.2
|
|
McGrath
|
27.5
|
27.4
|
0.1
|
|
Nome
|
26.7
|
27.4
|
-0.7
|
|
St. Paul Island
|
35.1
|
35.4
|
-0.3
|
|
Talkeetna
|
34.3
|
36.0
|
-1.7
|
|
Valdez
|
38.4
|
39.0
|
-0.6
|
|
Yakutat
|
41.0
|
40.3
|
0.7
|
Table A: Mean temperature for 2011, normal temperature
(1981-2010) and deviations from the mean for the 20 first order meteorological
stations in for Alaska
The mean deviation of temperatures by month is presented in
Figure 2 for the 20 stations. The figure shows, that January and October were
warmer than normal with positive deviations of above 2¡F. All other stations
were within 2¡F deviations, be it positive or negative, with the exception of
November,
Figure 2: Mean monthly temperature deviation for the 20
first order stations in Alaska by month.
which was much colder than normal. The deviation of 6.7¡F for
the mean of the 20 stations is remarkable, and shows that all of Alaska was too
cold during this month and it was indeed colder than December, an infrequent
occurrence.
Precipitation
The mean annual precipitation of the 20 stations was 36.03Ó, which
is close to the long-term mean of 36.86Ó. As reported previously (Shulski and
Wendler 2007), there is a very large variation in the precipitation amount,
when going from the southeast, e.g. Yakutat reported in 2011 122.80Ó, to the
North (Barrow) with an annual value for 2011 of 6.59Ó. It is even more
remarkable, that for 2011 Barrow reported 145% of normal precipitation, a value
which is, when expressed as a percentage, only surpassed by Kotzebue (149%) in
northwest Alaska. This large gradient in precipitation explains the fact, that
the most glaciers are found in southern Alaska, calving partly in the Ocean,
while in the Brooks Range in Northern Alaska, the temperatures are much colder,
and glaciers are not as frequent and smaller in size. In Fig. 3 the
precipitation values are presented in graphical form, but we did not analyze
the data with isolines, as
Figure 3: Precipitation deviations (%) from the normal
(1981-2010) for 2011 based on all Alaskan 1st order meteorological
stations.
large variations can occur over short distances, especially in
the summer due to shower activities. The graph shows, that northwestern Alaska
observed far above normal precipitation values, while southwestern Alaska
recorded values below normal. For the rest of Alaska the results were mixed,
but dominantly below normal. More details can be seen from Table B, in which
the actual deviations by month and year are presented for all stations.
|
Station
|
|
|
|
|
Observed
(in)
|
Normal
(in)
|
Delta
(in)
|
Delta
%
|
|
Anchorage
|
|
17.16
|
16.58
|
0.58
|
3%
|
|
Annette
|
|
113.65
|
101.63
|
12.02
|
12%
|
|
Barrow
|
|
6.59
|
4.53
|
2.06
|
45%
|
|
Bethel
|
|
16.52
|
18.54
|
-2.02
|
-11%
|
|
Bettles
|
|
19.65
|
14.90
|
4.75
|
32%
|
|
Big Delta
|
|
8.58
|
11.62
|
-3.04
|
-26%
|
|
Cold Bay
|
|
39.41
|
41.67
|
-2.26
|
-5%
|
|
Fairbanks
|
|
9.52
|
10.81
|
-1.29
|
-12%
|
|
Gulkana
|
|
11.65
|
11.26
|
0.39
|
3%
|
|
Homer
|
|
23.24
|
24.34
|
-1.10
|
-5%
|
|
Juneau
|
|
66.66
|
62.27
|
4.39
|
7%
|
|
King Salmon
|
|
23.89
|
19.49
|
4.40
|
23%
|
|
Kodiak
|
|
70.53
|
78.00
|
-7.47
|
-10%
|
|
Kotzebue
|
|
16.38
|
11.00
|
5.38
|
49%
|
|
McGrath
|
|
19.08
|
18.00
|
1.08
|
6%
|
|
Nome
|
|
18.43
|
16.81
|
1.62
|
10%
|
|
St. Paul Island
|
|
25.40
|
23.67
|
1.73
|
7%
|
|
Talkeetna
|
|
23.81
|
27.97
|
-4.16
|
-15%
|
|
Valdez
|
|
67.62
|
69.03
|
-1.41
|
-2%
|
|
Yakutat
|
|
122.80
|
155.12
|
-32.32
|
-21%
|
Table B: Observed precipitation for 2011, normal precipitation
(1981-2010) and deviations from the mean for the 20 first order meteorological
stations in for Alaska
The mean deviation of precipitation by month is presented in
Figure 4 for the mean of the 20 stations. The figure shows, that February and
December were wetter than normal with positive deviations of above 60%, while
March and May were much drier than the norm.
Figure 4: Mean monthly precipitation deviation for the
20 first order stations in Alaska by month.
Snow
Precipitation falls in summer as rain, but in winter as snow. ÒWinterÓ
is, of course, much longer in Northern Alaska, e.g. Barrow when compared to the
Southeast, e.g. Annette. In Fig.5 the annual snowfall for the stations is
presented. It should be pointed out, that 4 stations did not report snowfall
amounts, namely Big Delta, Gulkana, Homer and Talkeetna.
Figure 5: Mean annual snowfall deviations for 16 first
order meteorological stations in Alaska
It
can be seen that 2 stations, Kotzebue and Barrow, both situated in northwestern
Alaska, measured more than twice the expected amount of snowfall. It might not
be surprising, that this is the area where the highest positive temperature
deviation was observed, and warmer air is able to hold a larger amount of water
vapor when compared to a colder air-mass. Generally, snowfall was above the
long term mean for most stations. The only strong negative deviation with -38%
was found for Cold Bay. The detailed numbers can be obtained from Table C.
|
Station
|
|
|
|
Observed
(in)
|
Normal
(in)
|
Delta
(in)
|
Delta
%
|
|
|
Anchorage
|
77.6
|
74.5
|
3.1
|
4%
|
|
|
Annette
|
29.3
|
34.9
|
-5.6
|
-16%
|
|
|
Barrow
|
77.1
|
37.7
|
39.4
|
105%
|
|
|
Bethel
|
72.8
|
61.8
|
11.0
|
18%
|
|
|
Bettles
|
129.0
|
91.4
|
37.6
|
41%
|
|
|
Big Delta
|
|
54.2
|
|
|
|
|
Cold Bay
|
45.5
|
73.1
|
-27.6
|
-38%
|
|
|
Fairbanks
|
63.6
|
65.0
|
-1.4
|
-2%
|
|
|
Gulkana
|
|
58.4
|
|
|
|
|
Homer
|
|
47.4
|
|
|
|
|
Juneau
|
114.1
|
86.7
|
27.4
|
32%
|
|
|
King Salmon
|
60.7
|
46.6
|
14.1
|
30%
|
|
|
Kodiak
|
83.9
|
68.9
|
15.0
|
22%
|
|
|
Kotzebue
|
137.2
|
59.8
|
77.4
|
129%
|
|
|
McGrath
|
104.8
|
97.3
|
7.5
|
8%
|
|
|
Nome
|
101.8
|
75.7
|
26.1
|
34%
|
|
|
St. Paul Island
|
60.9
|
59.8
|
1.1
|
2%
|
|
|
Valdez
|
356.1
|
326.3
|
29.8
|
9%
|
|
|
Yakutat
|
164.1
|
143.4
|
20.7
|
14%
|
|
Table C: Observed snowfall for 2011, normal snowfall (1981-2010)
and deviations from the mean in % for the 16 first order meteorological
stations of Alaska
Finally, enclosed is a review on a monthly basis, which was
taken to a great extent from our Statewide Summaries, which are also available
from our website: http://climate.gi.alaska.edu/
January 2011 started out as a pleasant month. 18 of the 20
stations recorded above normal temperatures, with large positive deviations in
northwestern Alaska. Nome reported the largest deviation with 9.7¡F, followed
by Kotzebue (+6.9) and Bethel (+5.0¡F). The two stations with negative mean
monthly temperature deviations were found in southeastern Alaska in Annette
(-1.1¡F) and Juneau (-0.1¡F). The highest temperature for the month of 49¡F was
measured at Merrill Field, Anchorage on the 2nd, and then in Palmer
a day later. JanuaryÕs lowest temperature of -58¡F occurred at Chicken on the
Taylor Highway, and at Ft. Yukon at the banks of the Yukon River, both
happening on the 21st of the month.
Precipitation in January was normal with 98% of the expected
value. Gulkana and Kotzebue were relatively the wettest with nearly twice the
expected values, while on the other side of the coin, Fairbanks and Big Delta
had roughly 1/3rd of the normal values. Little Port Walter, the station with
the highest annual amount of precipitation in Alaska, also held the record for
January with 23.94Ó. The greatest snow depth of 112Ó occurred on the 22nd
January at the top of Eaglecrest, a ski area close to Juneau.
February was generally cold in Alaska with a mean deviation of
-1.5¡F; 13 of the 20 stations were seasonably below normal. The strongest
negative deviations in declining order were Big Delta (-7.0¡F), Fairbanks
(-5.2¡F) and Bettles (5.0¡F), all situated in Interior Alaska. In contrast to
this, Northern Alaska was much warmer than normal. Barrow recorded a mean
temperature of -6.1¡F, a substantial deviation of +8.3¡F above the long
term mean. On the 24th a new high temperature record of 29¡F was
reported, a balmy temperature for the northernmost town in the USA. The old
record of 1982 was smashed by 8¡F. To surpass the old record by such an amount
is remarkable, especially as the observation length is close to a
century. Several new daily records were set, 3 of those for Kotzebue,
however, we will not discuss those in detail in an annual review.
Precipitation was substantially higher than average, with 168%
of normal values. The largest amount of deviation in declining order were
observed in Kotzebue (556%), Barrow (443%), Fairbanks (386%), Gulkana (310%)
and Bettles (258%), all located in Northern or Interior Alaska. In contrast to
this, South Central and the Aleutians measured precipitation below the normal
mark for February. Daily new records were found for a number of stations, but
we report here only one: on the 17th February 1.37Ó of precipitation
were recorded for Kotzebue, surpassing the old record of 1996 (0.14Ó) by nearly
10 fold. The amount observed for this day is very close to the normal amount
(1.40Ó) for the whole month. It was also a record in snowfall at 9.9Ó and this
precipitation event in connection with strong winds closed Kotzebue down.
March temperatures for
most of Alaska were below normal. The mean deviation calculated to -1.3¡F with
14 stations being below the long-term mean, one exactly at the mean, and 5
stations being above the normal. Those are in declining order: Barrow (6.3¡F),
Kotzebue (4.1¡F), St Paul Island (2.2¡F), Kodiak (0.9¡F) and Cold Bay (0.4¡F).
The strongest negative deviations were found in the Interior with -9.9¡F at
Gulkana and in the Southeast with -5.0¡F at Juneau. Temperatures were highly above normal this March
north of the Books Range and along the West Coast, the Pribilof and Aleutian
Islands, while temperatures for the Interior, Southwest, South Central and
Southeast were all below to near normal. Nevertheless, new high temperature
records were set towards the end of March, all in the Southeast. There
are too many to mention all, but the highest temperature was reported at
Klawock on the 25th reaching a high of 58¡F and surpassing the old
record of 52¡F set in 2004.
Precipitation was below normal for most of the
state with the mean value for the 20 stations being 56% of normal. Exceptions were
the Arctic and St. George Island. The March precipitation deviations are as
follows: Barrow recorded 0.28"; the normal for March is just 0.09Ó, making
this a positive deviation of +211% above normal. The stations showing negative
deviations are Talkeetna reported 0.14Ó (-89%), King Salmon 0.10Ó (-87%), Big
Delta 0.04Ó (-82%), Juneau 1.28Ó (-64%), Nome 0.24Ó (-60%), Fairbanks 0.15Ó
(-46%), Anchorage 0.45Ó (-31%) and Ketchikan 10.05Ó (-10%). Of note, Valdez
reported the longest stretch of dry days since records began in 1972.
Twenty-two (22) days with no precipitation (since February 20th);
the previous record was 20-days, set in 1996.
AprilÕs
temperatures were above normal in Southern Alaska, the Interior was close to
normal and Arctic, Western and Southeast Alaska experienced temperatures below
the expected values.
The temperature in Anchorage averaged 37.5¡F, a
+1.2¡F deviation from the normal value. Fairbanks recorded 31.8¡F, a small
positive deviation of 0.1¡F and Big Delta was temperature-wise very similar
with 32.3¡F with a positive deviation of 0.2¡F. Below normal temperatures were
measured in Nome 17.9¡F (deviation -1.7¡F), King Salmon 32.6¡F (deviation
-0.5¡F), Juneau 39.1¡F (deviation -1.7¡F) and Ketchikan 41.0¡F (deviation -2.0¡F).
Remarkable was Barrow on the Arctic coast. After 9 consecutive months of above
normal temperatures, the monthly mean of -1.0¡F was slightly (deviation -0.5¡F)
below the 30 year norm.
Precipitation was below normal for most of the
State with exceptions of western and southwestern Alaska. King Salmon reported
1.09Ó, or 116% of the normal value of 0.94Ó. In Nome, further north along the
Bering Sea coast, the precipitation (0.64Ó) was very close to normal, 99% of
the expected value of 0.65Ó. Barrow showed the strongest negative deviation
with only 17% of the expected value. However, it should be pointed out that the
precipitation is light in Northern Alaska, especially in spring, when
cloudiness is at a minimum. The precipitation for the month was 0.02Ó water
equivalent, while the monthly norm is 0.20Ó. From these values it can be easily
deduced, that one single snowfall could substantially change these
statistics. Other stations gave the following values expressed again as the
percentage of normal: Fairbanks 33%, Juneau 62%, Ketchikan 63%, Anchorage 77%
and Big Delta 85%.
MayÕs temperatures were above normal for much of
Alaska, with a mean value for all stations of 1.0¡F. Deviations from the mean
were especially pronounced for Northern and Interior Alaska. Here are the
temperatures given in order of declining deviations from the norm. Fairbanks
held the record for the month with 52.4¡F, 2.9¡F above the normal. The
temperature in Big Delta averaged 50.5¡F, a +2.4¡F deviation from the normal
value. The same deviation of +2.4¡F was found for Barrow, which recorded a mean
monthly temperature of 22.5¡F. King Salmon reported 32.6¡F (deviation -0.5¡F),
Ketchikan 45.1¡F (deviation +1.6¡F), Anchorage 48.4¡F (deviation + 1.5¡F), Nome
38.4¡F (deviation +1.3¡F), Ketchikan 48.9¡F (deviation +0.4¡F) and Juneau
48.2¡F (deviation +0.3¡F). Northern Alaska resumed its warming trend with
Barrow, which last month had a negative temperature deviation, the first in 10
months, which was once again warmer than the long term mean. May was also the first month
of the year where the Interior became warmer than the southern region, which is
rather typical for the relatively warm continental summer conditions of the
Interior. For example, the monthly mean temperature for Fairbanks was 52.4¡F,
with a monthly maximum of 86¡F on the 28th. In contrast to this, the
mean monthly temperature of Anchorage was 48.4¡F, and a maximum of 70¡F, which
occurred on 26 and 27 May.
Precipitation was below normal for most of the
State with a mean value 63% of normal. Exceptions could be found in parts of
South Alaska, where King Salmon reported 143% and Ketchikan 111% of normal.
Below normal precipitation were recorded for Fairbanks (7%), Big Delta (22%),
Anchorage (50%), Barrow (75%), Nome (78%), Juneau (81%). It should be pointed
out that precipitation is light in Interior and especially Northern Alaska in
spring, when cloudiness is at a minimum. The above normal temperatures and far
below normal precipitation values in Interior Alaska caused very dry surface
conditions, enhancing wildfires ignition and spreading, and by the end of the
month a great number of wildfires had occurred, far above normal for the time
of year.
JuneÕs
temperatures were generally close to normal for all of Alaska: the mean deviation
from the normal was -0.2¡F. Nome measured 49.2¡F, having the greatest positive
deviation of 1.9¡F. Other stations with positive deviations in declining order
were Ketchikan with 48.7¡F (deviation + 1.2¡F), Fairbanks with 60.4¡F
(deviation also +0.7¡F), Barrow with 35.2¡F (deviation +0.2¡F) and Juneau with
57.5¡F (deviation +0.1¡F). For Big Delta the June temperature matched the
long-term mean of 57.5¡F, while Anchorage with 54.0¡F (deviation - 0.7¡F) and
King Salmon with 48.7¡F (deviation -2.2¡F) were colder when compared to the
30-year norm.
Fairbanks reported on the 25th of June
a temperature of 88¡F. While not a new maximum for the day, it was remarkable
insofar, that strong thunderstorm activity was reported in the evening and
4,300 lightning strikes were recorded for this day, which ignited 10 new
wildfires in the Interior Alaska. No new high temperatures were set in June in
Alaska, however, on the 16th of June a minimum temperature of a
chilly 38¡F was observed for Valdez, which was cooler than the old record low
of 41¡F, which was set in 1985. Further, Bethel Airport reported on the 28th
June a maximum temperature of 47¡F. This is a very low maximum temperature of
the day, and one has to go back to 1952 to find the same low temperature. King
Salmon reported 30¡F on the 2nd of June, and was the last day of
frost. This tied the record low for the day, which was previously set in
1991 and the low temperature of 35¡F on the 23rd of June broke the
old record set in 1949 by one degree.
Precipitation was varied with about half the
stations reporting above normal values, while the rest were seasonably too dry.
Precipitation values are expressed as percentages of normal; this means that
values above 100% are amounts above the expected values, while values below
100% indicate a shortage of precipitation when compared to the long term mean.
King Salmon in southwestern Alaska reported 2.77Ó, or 163% of the normal of
0.94Ó. In Nome, further north along the Bering Sea coast, the precipitation
(0.86Ó) was 75% of normal. Barrow in the Arctic, reported 0.54Ó, which
represent 169% of normal, as the precipitation is light north of the Brooks
Range. Fairbanks recorded 1.77Ó or 126% of normal. However, substantially more
precipitation was recorded in the upper Chena Basin; large variations are
typical for the summer season for the Interior region, due to shower activity
caused by thunderstorms, which are more patchy than precipitation due to
frontal activity. The Chena River was close to flood stage, and on the Salcha
River some minor flooding did occur. Juneau reported 4.25Ó, or 126% of normal.
On the 14th 1.03Ó of rain was measured, a new record for this day,
surpassing previous maximum amount of 0.66Ó, recorded in 1951. Ketchikan had a
monthly sum of 2.84Ó, only 41% of the expected value, as southeast Alaska
experiences a large amount of rain. The Anchorage precipitation value (1.19Ó)
was 112%, which is slightly above normal. Precipitation (2.00Ó) was below
normal for Big Delta, totaling 81% of the expected amount. However, on the 28th
June a new record rainfall was observed with a total 0.74Ó, surpassing the old
record for the day of 0.42Ó, which was set in 1948.
A strong storm was observed in the Aleutians in
late June, and new record wind speeds were recorded at Cold Bay. On the 23rd
of June, a gust of 31 mph was recorded, surpassing the old record by 1
mph. On the 25th a gust of 51 mph was observed, surpassing the
previous value of 45 mph set in 2007, and once again on the following day, a
new daily record of 58 mph was observed, again surpassing the previous value of
45 mph, which had also been set in 2007.
JulyÕs
temperatures were generally close to normal for all of Alaska with the
exception of the Bering Sea Region, which was much colder than normal.
Nome measured 48.6¡F, having the greatest negative deviation of 4.0¡F, followed
by King Salmon (-3.7¡F). Other stations with negative deviations in declining
order were Ketchikan with 56.8¡F (deviation -0.9¡F), Juneau 55.9¡F (deviation
also -0.9¡F), Fairbanks with 61.7¡F (deviation -0.8¡F) and Anchorage 57.8¡F
(deviation -0.6¡F). Barrow, which has had a strong temperature increase
over the last decade, measured 41.9¡F, a positive deviation of 1.5¡F, while Big
DeltaÕs July temperature was 1.0¡F above the normal of 57.5¡F.
Precipitation was varied, but was generally above
normal. Nome and Ketchikan were very wet with nearly twice the monthly
precipitation, while Kodiak was drier than average. In the Interior, where
thunderstorms and showers frequently occur in the summer, large variation in
the amount of precipitation can be found over short distances. For
example, Fairbanks reported 1.73Ó, just a tiny amount (2%) below normal, while
at Angle Creek in the upper Chena Basin 4.83Ó were measured. Further, the rainfall in Ketchikan in the 1st
of the month was remarkable with an amount of 3.69", setting a new record
for this day. It surpasses the old record by about 1/3, which was set in 1917
at 2.49".
Early in the month, a strong storm occurred in
the Bering Sea. In Cold Bay, in the Aleutians, a peak wind speed of 54 mph was
recorded on the 5th July, surpassing the previous wind maximum of
this day (44 mph) set in 2009. The following day a peak wind speed of 49 mph
was reported breaking the old record in 2009 by 5 mph. On the 8th
July a peak wind speed of 54 mph was measured, surpassing the old record of
2008 by 3 mph.
August was seasonally cooler than
normal in Alaska with 17 of the 20 stations reporting below normal values. The
mean monthly deviation of all stations was 1.1¡F below the long-term climatic
value. High negative deviations (<-2¡F) were
observed in declining order for Juneau (-2.9¡F), King Salmon (-2.5¡F) and Nome
(-2.1¡F), while
Barrow (+3.1¡F) was substantially warmer and no frost occurred at that station in August, which is unusual. The only other 2 stations, which reported above
normal temperatures were Fairbanks (+1.1¡F) and Yakutat (+0.6¡F), an indication
that negative
deviations were widespread and fairly uniform.
Precipitation was for most stations
above normal in August, with a maximum in Southeast Alaska, reporting nearly
twice the expected amount. The mean value for all stations was 25% above
normal. 65% of the stations gave above normal values, while 35% were drier. Far
above normal values were reported for Annette (210%), Juneau (187%) and Kodiak
(163%), while Cold Bay was the driest with 64% of the expected amount. In
Juneau, precipitation totaled 10.72". This value came close to the
maximum amount ever observed in August, which was set in 2006 at 11.02Ó. As
might be deduced from the high precipitation amount in Juneau, sky cover
averaged 90%, with 30 cloudy days and some rain occurring on 28 days of the
month.
September was seasonally warmer in Alaska
with 13 of the 20 stations reporting above normal values. The mean monthly
deviation of all stations was 1.1¡F above the long-term climatic value. High positive deviations (>2¡F) were observed in declining order
for Barrow (4.6¡F), Fairbanks (4.3¡F), Bettles (4.0¡F), Big Delta (3.9¡F), McGrath
(3.0¡F), Nome and Kotzebue (both 2.3¡F). As the month before, Barrow in
the North recorded the highest monthly positive deviation. Temperatures below
the long-term mean were measured at coastal stations, they were fewer in amount
when compared to the positive values. Here we list of the stations with more
than 1¡F negative deviation in declining order: Cold Bay (-2.0¡F), Homer
(-1.4¡F) Juneau and St Paul Island (both -1.2¡F).
Even of greater
importance than the generally above normal temperatures, was the late
occurrence of frost, especially for gardeners and agriculture. No temperature
below the freezing point (32¡F) was observed during September for Juneau,
Ketchikan and Anchorage; however, on the 26th a minimum temperature
of 32¡F was observed for the latter station. Furthermore, the 26th
of September brought the first frost to Fairbanks, Big Delta and King Salmon.
Precipitation was mostly below normal
in September. Only 3 stations were substantially wetter than normal, namely
Kodiak (213%), Annette (192%) and Barrow (128%) of normal. Yakutat (deviation
from norm -3%) and Juneau (+1%) were very close to normal, while the other 15
stations gave below normal values, with many stations less than half of the
expected values, especially in Interior Alaska. Gulkana measured 23% of normal,
Talkeetna 25%, Anchorage and Big Delta each 26%, to mention only the most
extreme. The mean of the 20 stations gave a value of 75% of normal.
October was a pleasant month for most
of Alaska with 16 of the 20 stations reporting above normal temperatures.
Bettles (+6.5¡F), Barrow (+5.6¡F), McGrath (+5.4¡F), Fairbanks (+4.7¡F) and Big
Delta (+4.3¡F) were especially warm, when compared to the 30-year mean. Even
the four stations, which were seasonally too cold, were still close to normal
with the following values: Nome (-0.7¡F), St Paul Island (-0.3¡F), Juneau
(-0.2¡F) and Annette (-0.1¡F). The mean value of the 20 stations was calculated
as a positive temperature deviation of 2.3¡F.
Precipitation records for October were
mixed, 10 stations recorded values above the expected value, while 10 stations
were below the norm. The mean of the 20 stations gave the exact long-term mean
value. Only 3 stations were substantially wet, namely Barrow (276%), Kotzebue
(173%) and King Salmon (156%) of normal. Less than half of the expected
precipitation values were observed especially in Interior Alaska. Big Delta
measured 24% of normal, Gulkana 36% Fairbanks 39% and Talkeetna 40%.
November was substantially colder than
normal in Alaska with all stations reporting below normal values. The mean
monthly deviation of all stations was 6.8¡F below the long-term climatic value.
This is in contrast to the previous month, when 79% of the stations reported
temperatures above the long term mean. Very high
negative deviations were observed in declining order for Big Delta (-11.1¡F),
McGrath (-11.0¡F), Fairbanks and Talkeetna (both -10.8¡F), Bethel (-10.2¡F),
Nome (-9.5¡F), Homer(-8.4¡F), Anchorage (-8.2¡F) and Kotzebue (-8.0¡F). It can
be seen that the largest deviations were found in the Interior and western
Alaska. Stations relatively close to the long term mean, but nevertheless colder
than normal, were: St. Paul Island (-0.6¡F), Barrow (-0.9¡F) and Cold Bay
(-1.1¡F), all coastal or island stations. Coastal stations are under the
maritime influence, as the large water body nearby makes deviations less
pronounced. However, this was not the case for all stations, see for example
Nome.
There were 2 major
events, which occurred during the month. First, at the beginning of the month,
a strong storm occurred, associated with record high wind speeds and a large
amount of snowfall. This event was pronounced in South and West Alaska.
Secondly, shortly after the middle of the month, the advection of an arctic
air-mass brought record low temperature to most of Alaska. This event caused
the temperatures to be much colder than expected for November. Numerous new
record low temperatures were reported. For Fairbanks the coldest temperature
occurred on the 17th with -41¡F. In November temperatures below
-40¡F are seldom observed in Interior Alaska, and for Fairbanks one has to go
back to 1994 to find such a low temperature. The absolute record low during the
cold spell is held by Manley Hotsprings, some 100 miles WNW from Fairbanks with
a value of -54¡F.
Precipitation records for November
were mixed, 8 stations recorded values above the expected value, while 12
stations were below the norm. The mean of the deviations expressed as
percentages gave exactly a value of 0%. Only 2 stations were substantially wet,
namely Anchorage with 100% and King Salmon with 96% above normal. At the other
end of the scale were Big Delta and Nome with 40% of the expected value,
followed by Bettles (51%), Homer (57%) and Talkeetna (58%). At first glance, the
normal precipitation value for Alaska as a whole is surprising, as Alaska was
much colder in November, hence less than normal precipitation might be
expected. However, at the beginning of the month, a strong storm hit Alaska,
bringing large amounts of rain and snow to places. On the 1st of November
the storm hit South Alaska. The only road connection of Valdez to the rest of
Alaska had to be closed in the Thompson Pass area. Wind speeds in the area were
85 mph, with gusts up to 120 mph. Visibility was extremely poor. In Juneau and
the Kenai Peninsula (Homer, Soldotna, Kenai, Nikiski, Sterling, Kasinof) power
outages were reported due to downed transmission lines. Somewhat later, snow
and hurricane-force winds battered the Alaskan West-Coast. It was the strongest
storm in nearly 40 years, ripping off roofs and forcing some residents to board
their windows and look for higher ground. On St. Paul Island the wind speed
reached 70 mph, which set a new record for any November. In some of the native
villages (e.g. Tunanak and Kipnuk) the water reached some homes. However, on
the positive side, the 14ft rock seawall, which was built to protect the
village of Kivalina from coastal erosion, held.
December
brought relief with mostly above normal temperatures after the extremely cold
November. Twelve of the stations were seasonally above normal, with very high
positive deviations. In declining order these are: Gulkana (11.1¡F), Fairbanks
(8.1¡F), Big Delta (7.5¡F), McGrath (6.9¡F) and Anchorage (4.4¡F). The 8
stations which were seasonally below normal were much closer to normal, with a
maximal deviation of -3.0¡F observed for Nome. The mean monthly deviation of
all stations could be calculated as 2.1¡F above the long-term climatic value.
Normally, the 3 winter months of December,
January and February are the coldest of the year, which can be clearly seen
from the long-term averages. However, in 2011 15 of the 20 stations analyzed
were colder in November than in December, which is quite unusual. In addition,
one station (Kodiak) had the identical temperature of 28.4¡F for both months.
The greatest difference in temperature was found in Gulkana (12.7¡F) and
Fairbanks (12.2¡F), with December being substantially warmer than November. Not
only the mean temperatures, but also the minima were frequently lower in
November than in December. In general, for the first two-thirds of December,
above normal temperatures were observed, but during the last 10 days of the
month the temperature dropped sharply, with lower monthly minima observed
towards the end of the month.
Precipitation totals for December were in general
above average; 18 stations measured values above expectation, while only two
stations were below the norm, one of these only slightly so (Annette -4%). The
other (Kodiak) recorded a lower value by -38%. The mean of the deviations
expressed as percentages gave a value of +78%, a substantial deviation for such
a large area as Alaska, or differently expressed, Alaska was wet in December
with, on average, nearly 80% additional rain or snowfall. The most extreme
values expressed as percentages above normal were found in Barrow (329%),
Bettles (251%), McGrath (162%), Kotzebue (146%), Anchorage (138%) and
Talkeetna (111%).
Looking at snowfall, again expressed as
percentage above or below normal, Barrow had the highest deviation (+349%),
followed by Kotzebue (+205%) and Valdez (+112%). On the other side of the
spectrum, Annette, in the southeast corner of Alaska, reported a deviation of
-64%. However, it should be pointed out that only 15 of the 20 stations
supplied snowfall observations.
December brought quite a number of special events.
A storm brought strong winds, warm air and precipitation. On the 1st
of December a temperature of 54¡F was recorded in Big Delta, a new record for
this day, smashing the old record of 42¡F set in 1976. An increase in a record
by 12¡F is rare, and this was an extraordinary event. It was caused by strong
southerly flow across the Alaska Range –so called Chinook winds, which
are gusty. The air is cooled moist-adiabatical when it rises due to
precipitation on the south side, but descends dry-adiabatical on the north side
of the range. As the dry adiabatical rate is higher than the moist-adiabatic
rate, the air arrives warmer in Interior Alaska, when compared to the
temperature it started out with on the south side of the Range.
The storm, which moved over Alaska at the
beginning of the month, brought a wind gust of 74 mph on the 3rd of December
at St. Paul Island in the Southern Bering, and two days later a gust of 118mph
was recorded at Glen Alps. On the 4th, the maximum temperature of
+47¡F was recorded in Fairbanks - a balmy temperature, for Interior Alaska in
winter. A mean temperature for the day was 37¡F, a rare event, as mean daily
temperatures above freezing are infrequent in winter in Fairbanks. Also on the
4th, at Barrow in Northern Alaska, average wind speeds were recorded
at 30 mph, with gusts exceeding 50 mph. These are high, uncommon values,
however they do not represent new records. More unique was the precipitation
record of Barrow with 0.33" (water-equivalent), beating the previous
record for the 4th December of 0.19 set in 1922. This was associated
with a new snowfall record of 6.5", surpassing the old record of 2.5"
set on the same day in 1922. Both these values are in fact new records for
all days in December. The previously highest precipitation amount for any
day in December had occurred on 13th December 1930 with 0.26",
and the highest amount of snowfall (5.0") had been observed on 29th
December 1922. Also Nome and Kotzebue reported new snowfall and precipitation
records. Further, in Valdez 2.80Ó of precipitation were recorded on the 4th,
which more than doubled the old record of 1.37Ó set in 1984.
Shulski, M., and Wendler, G. 2007. The Climate of
Alaska. Fairbanks: University
of Alaska Press.
Wendler, G. and Shulski, M. 2010. A Century of
Climate Change for Fairbanks,
Alaska. Arctic 62(3): 295-300.
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