2001 Juneau, Alaska (JNU)

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2001 JUNEAU, ALASKA (JNU)

Juneau lies well within the area of maritime influences which prevail over the coastal areas of southeastern Alaska, and is in the path of most storms that cross the Gulf of Alaska. Consequently, the area has little sunshine, generally moderate temperatures, and abundant precipitation. In contrast with the characteristic lack of sunshine there are greatly appreciated intervals, sometimes lasting for several days at a stretch, during which clear skies prevail. The rugged terrain exerts a fundamental influence upon local temperatures and the distribution of precipitation, creating considerable variations in both weather elements within relatively short distances.

Temperature variations, both daily and seasonal, are usually confined to relatively narrow limits by the dominant maritime influences. There are, however, periods of comparatively severe cold, which usually start with strong northerly winds, and are most often caused by the flow of cold air from northwestern Canada through nearby mountain passes and over the Juneau ice field. These are generally of brief duration. During such periods strong, gusty winds, known locally as Taku Winds, often occur especially in downtown Juneau, Douglas, and other local areas, but generally they are not felt in the Mendenhall Valley. At times these are strong enough to cause considerable damage. During periods of calm or light winds, temperature differences within short distances are frequently very pronounced. Variations in local sunlight and air drainage patterns produce wide differences in temperatures particularly between upland or sloping areas and areas of low, flat terrain. Juneau International Airport, located on low, flat terrain formed by the Mendenhall River delta, and in the path of drainage air from the Mendenhall Glacier, averages about 10 days a year with minimum readings below zero. Downtown Juneau, located on a sloping portion of a rugged mountain area, experiences on the average only about one day each year with minimum readings below zero. At the airport the growing season averages 146 days, from May 4 to September 28, while the downtown average is 181 days, from April 22 to October 21.

The months of February to June mark the period of lightest precipitation, with monthly averages of about 3 inches. After June the monthly amounts increase gradually, reaching an average of 7.71 inches in October. Due to the rugged topography, precipitation throughout the year tends to vary greatly within short distances. At the Juneau Airport, yearly precipitation is 53 inches while downtown, only 8 miles away, it is 93 inches. The maximum yearly amount received in the city is almost double the maximum received at the airport.

Although a trace of snow has fallen as early as September 9, first falls usually occur in the latter part of October, and sometimes not until the first part of December. On the average there is very little accumulation on the ground at low levels until the last of November, although at higher elevations, and particularly on mountain tops, a cover is usually established in early October. Snow accumulation usually reaches its greatest depth during the middle of February. Individual storms may produce heavy falls as late as the first half of May. However, snow cover is usually gone before the middle of April. Ice accumulations due to alternating thawing and freezing of snow or due to freezing precipitation are frequent problems in the Juneau area during the winter months.

NORMALS, MEANS, AND EXTREMES

JUNEAU, AK (JNU)

LATITUDE:     LONGITUDE:     ELEVATION (FT):     TIME ZONE:     WBAN: 25309

58 21′ 18″ N   134 34′ 30″ W   GRND: 37   BARO: 40   ALASKA (UTC + 9)  

ELEMENTPORJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECYEAR
TEMPERATURE FNORMAL DAILY MAXIMUM3029.434.138.747.255.160.963.962.755.947.136.731.646.9
MEAN DAILY MAXIMUM5229.134.138.747.355.261.763.862.856.147.037.732.547.2
HIGHEST DAILY MAXIMUM5757576172828690837361565490
YEAR OF OCCURRENCE195819921998199519471969197519991996198719491999JUL 1975
MEAN OF EXTREME MAXS.5242.743.948.259.469.775.978.475.665.655.648.143.958.9
NORMAL DAILY MINIMUM3019.022.726.732.138.945.048.147.342.937.227.222.634.1
MEAN DAILY MINIMUM5218.622.726.432.439.345.348.347.443.137.028.623.434.4
LOWEST DAILY MINIMUM57-22-22-156253136272311–5-21-22
YEAR OF OCCURRENCE197219681972196319721971195019481972198419661949JAN 1972
MEAN OF EXTREME MINS.52–.74.910.323.430.037.241.539.231.824.612.23.121.5
NORMAL DRY BULB3024.228.432.739.747.053.056.055.049.442.232.027.140.6
MEAN DRY BULB5224.028.432.739.947.253.556.155.149.642.033.228.040.8
MEAN WET BULB1427.128.232.538.644.750.450.249.745.438.730.928.138.7
MEAN DEW POINT1424.624.328.634.540.546.747.647.343.936.928.626.035.8
NORMAL NO. DAYS WITH:
MAXIMUM 70300.00.00.00.11.45.17.25.70.20.00.00.019.7
MAXIMUM 323016.38.74.30.10.00.00.00.00.00.36.812.949.4
MINIMUM 323025.421.822.014.43.50.10.0*1.47.219.123.9138.8
MINIMUM 0304.71.60.50.00.00.00.00.00.00.00.11.88.7
H/CNORMAL HEATING DEG. DAYS3012651025100175955836027931046870799011758897
NORMAL COOLING DEG. DAYS300000000000000
RHNORMAL (PERCENT)3080817977767881848888858382
HOUR 03 LST3081838687899090929391878488
HOUR 09 LST3080828076767882858889868382
HOUR 15 LST3077757063636772757982818274
HOUR 21 LST3081828280787881859190878383
SPERCENT POSSIBLE SUNSHINE3332323739393431322619232030
W/OMEAN NO. DAYS WITH:
HEAVY FOG (VISBY 1/4 MI)572.12.41.81.00.80.30.21.12.62.83.22.420.7
THUNDERSTORMS570.00.00.00.00.00.10.10.00.10.00.00.00.3
CLOUDINESSMEAN:
SUNRISE–SUNSET (OKTAS)476.26.46.46.46.36.56.66.36.87.06.76.76.5
MIDNIGHT–MIDNIGHT (OKTAS)155.25.76.15.96.36.16.25.96.46.66.06.16.0
MEAN NO. DAYS WITH:
CLEAR475.74.34.43.73.83.42.83.92.72.43.33.243.6
PARTLY CLOUDY472.63.03.24.24.44.24.54.73.32.12.32.040.5
CLOUDY4722.521.023.422.122.622.423.021.923.426.024.025.2277.5
PRMEAN STATION PRESSURE(IN)1629.8729.8829.7929.9029.9029.9930.0129.9829.8929.7929.7829.8029.88
MEAN SEA–LEVEL PRES. (IN)429.8729.9129.8229.9129.9330.0030.0429.9829.9129.7929.7829.8329.90
WINDSMEAN SPEED (MPH)357.88.18.18.58.27.97.57.47.99.38.78.98.2
PREVAIL. DIR (TENS OF DEGS)2009111111110808091111111111
MAXIMUM 2–MINUTE:
SPEED (MPH)345443937362426384141474447
DIR. (TENS OF DEGS)12121111121212121212121112
YEAR OF OCCURRENCE200120012000199920011999200119992001199920011999NOV 2001
MAXIMUM 5–SECOND:
SPEED (MPH)356514948473232485351615461
DIR. (TENS OF DEGS)12121212151012132012121212
YEAR OF OCCURRENCE200120012000199919992001200119992000199920011999NOV 2001
PRECIPITATIONNORMAL (IN)304.543.753.282.773.423.154.165.326.737.844.914.4454.31
MAXIMUM MONTHLY (IN)579.118.486.507.489.206.2210.3612.3115.1415.2511.2213.6115.25
YEAR OF OCCURRENCE199319641994199919921996199719611991197419561997OCT 1974
MINIMUM MONTHLY (IN)570.940.070.590.271.251.081.150.562.342.711.150.490.07
YEAR OF OCCURRENCE196919891983194819461950197219791965195019831983FEB 1989
MAXIMUM IN 24 HOURS (IN)572.742.711.812.052.302.262.462.623.354.663.403.564.66
YEAR OF OCCURRENCE194819931992199719921996200119741996194619881956OCT 1946
NORMAL NO. DAYS WITH:
PRECIPITATION 0.013018.116.517.916.716.815.916.117.320.023.719.220.2218.4
PRECIPITATION 1.00300.60.40.10.10.20.20.60.81.31.20.80.46.7
SNOWFALLNORMAL (IN)3030.618.615.43.50.*0.00.00.0T0.913.322.2104.5
MAXIMUM MONTHLY (IN)5769.286.352.646.31.2T0.00.0T15.669.854.786.3
YEAR OF OCCURRENCE1982196519481963196419701974195619941964FEB 1965
MAXIMUM IN 24 HOURS (IN)5720.123.731.024.20.7T0.00.0T8.819.425.631.0
YEAR OF OCCURRENCE1975194919481963194519701974195619941962MAR 1948
MAXIMUM SNOW DEPTH (IN)5138414033000007253641
YEAR OF OCCURRENCE1966194919721963195619941962FEB 1949
NORMAL NO. DAYS WITH:
SNOWFALL 1.0307.85.44.10.80.00.00.00.00.00.33.66.128.1
PRECIPITATION (inches) 2001 JUNEAU, AK (JNU)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19723.732.714.193.624.033.981.158.626.248.493.353.5653.67
19734.373.943.012.414.092.803.656.644.956.071.632.3045.86
19742.376.231.152.591.664.923.125.785.9615.257.797.0363.85
19754.103.762.173.043.592.484.962.787.253.552.835.8146.32
19768.194.823.612.143.423.372.483.168.326.195.155.5656.41
19774.594.563.314.021.563.473.193.035.577.144.582.1647.18
19781.711.501.842.192.863.183.984.393.0713.003.904.4646.08
19792.190.913.980.982.452.745.440.564.899.068.367.7349.29
19803.442.832.755.322.534.376.495.617.9111.267.102.2761.88
19814.662.571.882.113.272.444.256.1911.616.186.932.2454.33
19823.741.422.522.445.101.861.735.975.107.972.101.1741.12
19834.001.690.592.535.372.693.169.526.134.241.150.4941.56
19846.065.403.752.111.844.176.926.263.396.69
19858.33
19867.003.256.082.982.542.762.386.892.4012.335.966.4260.99
19873.993.132.122.082.606.022.544.548.9210.367.175.3258.79
19882.586.554.152.253.912.055.215.535.469.718.624.7560.77
19896.770.071.330.873.441.103.812.827.296.376.236.7846.88
19903.724.544.861.061.723.324.655.3510.636.594.896.0357.36
19914.166.554.414.734.723.414.859.6015.148.639.639.3285.15
19928.697.246.373.639.202.985.185.0211.455.907.915.7379.30
19939.118.093.501.942.194.922.253.208.449.0011.067.8971.59
19947.052.526.503.684.201.834.322.6811.179.159.576.2268.89
19951.782.833.012.082.853.454.365.017.436.042.934.5846.35
19962.268.434.122.191.806.223.167.9110.686.202.754.7360.45
19972.738.173.914.413.253.5110.363.938.267.854.6313.6174.62
19982.541.903.713.122.212.504.956.806.1712.131.725.4553.20
19998.142.662.587.485.692.694.106.7710.6212.195.7710.3078.99
20004.821.565.754.403.255.726.656.1210.0510.116.374.1768.97
20017.434.403.332.195.191.657.263.668.377.803.624.4959.39
POR=57 YRS4.293.723.552.923.493.124.425.197.227.975.454.8756.21
AVERAGE TEMPERATURE (F) 2001 JUNEAU, AK (JNU)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
197215.819.526.534.644.850.458.055.447.038.734.523.637.4
197318.924.632.939.645.951.353.751.848.041.223.028.038.2
197414.828.824.739.346.850.253.554.750.142.536.433.839.6
197523.124.530.638.347.451.455.953.951.441.828.524.739.3
197628.325.832.441.145.552.055.755.950.642.840.934.442.1
197735.040.136.042.347.754.157.058.550.542.429.418.942.7
197825.131.833.942.047.854.255.256.350.645.130.328.341.7
197920.611.035.641.147.752.256.758.251.045.237.226.540.3
198019.533.834.142.249.455.655.654.749.044.638.721.741.6
198137.632.739.439.152.154.356.155.949.242.836.826.943.6
198213.821.331.837.145.456.357.754.850.342.230.631.639.4
198330.231.834.842.649.755.657.154.648.042.131.818.941.4
198432.039.643.149.153.555.555.350.040.5
198532.5
198634.328.735.337.346.654.356.854.450.745.830.536.042.6
198733.134.731.841.647.851.658.657.550.144.440.034.343.8
198827.032.637.641.748.554.053.853.948.244.136.231.342.4
198925.523.929.442.749.055.460.158.252.441.732.936.042.3
199026.425.136.442.749.755.059.358.151.240.726.423.741.2
199124.935.333.141.748.255.055.255.050.340.136.333.642.4
199235.732.736.941.146.455.257.056.046.840.538.425.642.7
199324.530.235.844.452.155.859.657.151.245.836.835.944.1
199427.718.436.743.348.154.957.459.350.243.329.427.741.4
199527.229.030.343.451.455.457.054.853.832.425.2
199616.629.032.840.748.754.157.754.748.940.231.326.540.1
199726.135.331.541.551.556.658.258.853.341.437.336.744.0
199824.537.135.042.450.155.957.554.249.442.833.127.942.5
199926.628.633.139.544.853.857.456.449.743.536.135.942.1
200026.531.736.339.746.953.055.354.449.041.937.731.242.0
200136.728.233.440.345.254.255.457.250.341.932.929.042.1
POR=57 YRS24.428.232.739.647.453.556.054.949.542.033.128.140.8

REFERENCE NOTES:

PAGE 1:

THE TEMPERATURE GRAPH SHOWS NORMAL MAXIMUM AND NORMAL MINIMUM DAILY TEMPERATURES (SOLID CURVES) AND THE ACTUAL DAILY HIGH AND LOW TEMPERATURES (VERTICAL BARS).

PAGE 2 AND 3:

H/C INDICATES HEATING AND COOLING DEGREE DAYS.

RH INDICATES RELATIVE HUMIDITY

W/O INDICATES WEATHER AND OBSTRUCTIONS

S INDICATES SUNSHINE.

PR INDICATES PRESSURE.

CLOUDINESS ON PAGE 3 IS THE SUM OF THE CEILOMETER AND SATELLITE DATA NOT TO EXCEED EIGHT EIGHTHS (OKTAS).

GENERAL:

T INDICATES TRACE PRECIPITATION, AN AMOUNT GREATER THAN ZERO BUT LESS THAN THE LOWEST REPORTABLE VALUE.

+ INDICATES THE VALUE ALSO OCCURS ON EARLIER DATES.

BLANK ENTRIES DENOTE MISSING OR UNREPORTED DATA.

NORMALS ARE 30–YEAR AVERAGES (1961–1990).

ASOS INDICATES AUTOMATED SURFACE OBSERVING SYSTEM.

PM INDICATES THE LAST DAY OF THE PREVIOUS MONTH.

POR (PERIOD OF RECORD) BEGINS WITH THE JANUARY DATA MONTH AND IS THE NUMBER OF YEARS USED TO COMPUTE THE MEAN. INDIVIDUAL MONTHS WITHIN THE POR MAY BE MISSING.

WHEN THE POR FOR A NORMAL IS LESS THAN 30 YEARS, THE NORMAL IS PROVISIONAL AND IS BASED ON THE NUMBER OF YEARS INDICATED.

0.* OR * INDICATES THE VALUE OR MEAN–DAYS–WITH IS BETWEEN 0.00 AND 0.05.

CLOUDINESS FOR ASOS STATIONS DIFFERS FROM THE NON–ASOS OBSERVATION TAKEN BY A HUMAN OBSERVER. ASOS STATION CLOUDINESS IS BASED ON TIME–AVERAGED CEILOMETER DATA FOR CLOUDS AT OR BELOW 12,000 FEET AND ON SATELLITE DATA FOR CLOUDS ABOVE 12,000 FEET.

THE NUMBER OF DAYS WITH CLEAR, PARTLY CLOUDY, AND CLOUDY CONDITIONS FOR ASOS STATIONS IS THE SUM OF THE CEILOMETER AND SATELLITE DATA FOR THE SUNRISE TO SUNSET PERIOD.

GENERAL CONTINUED:

CLEAR INDICATES 0–2 OKTAS, PARTLY CLOUDY INDICATES 3–6 OKTAS, AND CLOUDY INDICATES 7 OR 8 OKTAS. WHEN AT LEAST ONE OF THE ELEMENTS (CEILOMETER OR SATELLITE) IS MISSING, THE DAILY CLOUDINESS IS NOT COMPUTED.

WIND DIRECTION IS RECORDED IN TENS OF DEGREES (2 DIGITS) CLOCKWISE FROM TRUE NORTH. "00" INDICATES CALM. "36" INDICATES TRUE NORTH.

RESULTANT WIND IS THE VECTOR AVERAGE OF THE SPEED AND DIRECTION.

AVERAGE TEMPERATURE IS THE SUM OF THE MEAN DAILY MAXIMUM AND MINIMUM TEMPERATURE DIVIDED BY 2.

SNOWFALL DATA COMPRISE ALL FORMS OF FROZEN PRECIPITATION, INCLUDING HAIL.

A HEATING (COOLING) DEGREE DAY IS THE DIFFERENCE BETWEEN THE AVERAGE DAILY TEMPERATURE AND 65 F.

DRY BULB IS THE TEMPERATURE OF THE AMBIENT AIR.

DEW POINT IS THE TEMPERATURE TO WHICH THE AIR MUST BE COOLED TO ACHIEVE 100 PERCENT RELATIVE HUMIDITY.

WET BULB IS THE TEMPERATURE THE AIR WOULD HAVE IF THE MOISTURE CONTENT WAS INCREASED TO 100 PERCENT RELATIVE HUMIDITY.

ON JULY 1, 1996, THE NATIONAL WEATHER SERVICE BEGAN USING THE "METAR" OBSERVATION CODE THAT WAS ALREADY EMPLOYED BY MOST OTHER NATIONS OF THE WORLD. THE MOST NOTICEABLE DIFFERENCE IN THIS ANNUAL PUBLICATION WILL BE THE CHANGE IN UNITS FROM TENTHS TO EIGHTS (OKTAS) FOR REPORTING THE AMOUNT OF SKY COVER.

HEATING DEGREE DAYS (base 65 F) 2001 JUNEAU, AK (JNU)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972–732072935358109071275142311269867525844049302
1973–74343404505732125311431550100612427655564379936
1974–753493154376908519571296112910637915414028821
1975–76281337402712108812441132113110067065973849020
1976–772802754276797179389186908936735313207341
1977–782431964286951062142312339229546835253178681
1978–7929826242761210371134137015059047125283789167
1979–80251205415609830118714048959496784772788178
1980–8128330847262878313338438997867723923167815
1981–8226927546968284111751579121410218306012579213
1982–832203104356991027102910739249316634702758056
1983–8423731750270199114231014780649486338
1984–85286291444754
1985–8610019431011913822564316
1986–87249319423587102889198284110206975263947957
1987–8819922244063574494411699358446915083247655
1988-8933833849764185510401217114410976634912838604
1989-90159210370713959890119111098796614672957903
1990-911802104077481152127412388239816945162988521
1991–922943034357648559669029308657125712927889
1992-93240274540750791121712509668996123942718204
1993–94166240406588838891114712988696415142997897
1994–95229171437668106111501165100310666414162858292
1995–96241309329971122914931038993719498322
1996–9721831247676410041187119682610316984142528378
1997–9820318334572582386912477769266734572667493
1998–992243314636819511141118110129787586193298668
1999–0023026445266085889511849598827515523548041
2000–01295322471710813104087310269727346053208181
2001–2922354347099561111
COOLING DEGREE DAYS (base 65 F) 2001 JUNEAU, AK (JNU)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19720000000000000
19730000000000000
19740000000000000
19750000007000007
19760000003300006
19770000000100001
19780000000000000
19790000000100001
19800000010000001
19810000000000000
19820000020000002
19830000000000000
1984000000000
19850
19860000020000002
19870000005000005
19880000000000000
1989000000140000014
199000000183000012
19910000060000006
19920000060000006
19930000005000005
19940000000200002
199500000100000
19960000002000002
19970000060000006
19980000000000000
19990000002300005
20000000000000000
20010000000000000
SNOWFALL (inches) 2001 JUNEAU, AK (JNU)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972–730.00.00.02.22.831.663.820.99.60.50.00.0131.4
1973–740.00.00.0T18.615.736.032.815.30.50.00.0118.9
1974–750.00.0T0.93.517.341.516.518.94.50.00.0103.1
1975–760.00.00.05.332.551.032.934.125.52.30.00.0183.6
1976–770.00.00.01.21.126.35.0T12.7T0.00.046.3
1977–780.00.00.0T27.416.65.21.11.70.40.00.052.4
1978–790.00.00.00.014.921.624.221.45.4T0.00.087.5
1979–800.00.00.00.01.648.441.64.12.4T0.00.098.1
1980–810.00.00.00.00.540.52.416.40.52.20.00.062.5
1981–820.00.00.00.04.06.069.229.68.41.1T0.0118.3
1982–830.00.00.02.00.410.840.115.70.2T0.00.069.2
1983–840.00.00.00.08.113.343.10.71.0TT0.066.2
1984–850.00.00.00.0
1985–862.010.37.430.44.4T0.0
1986–870.00.00.0T22.11.43.31.47.3T0.00.035.5
1987–880.00.00.0T4.66.83.58.01.00.50.00.024.4
1988-890.00.00.00.04.811.344.70.210.0T0.00.071.0
1989-900.00.00.00.632.56.436.539.40.60.00.00.0116.0
1990-910.00.00.00.048.833.231.815.59.40.8T0.0139.5
1991–920.00.00.05.47.749.314.312.44.1TT0.093.2
1992-930.00.00.01.14.425.032.536.82.6T0.00.0102.4
1993–940.00.00.00.04.310.461.232.422.9T0.00.0131.2
1994–950.00.00.00.069.825.88.614.028.4T0.00.0146.6
1995–960.00.00.00.02.923.020.833.15.5T0.00.085.3
1996–970.00.00.00.52.54.612.317.319.20.40.00.056.8
1997–980.00.00.01.91.214.912.90.5
1998–9922.853.134.27.31.1T0.0
1999–000.00.00.0T5.119.913.64.6TT0.00.043.2
2000–010.00.0T2.31.02.37.614.90.6TT0.028.7
2001–0.00.00.03.43.125.5
POR=55 YRS0.00.0T1.012.222.325.218.614.22.90.0T96.4

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