2001 Hilo, Hawaii (ITO)

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2001 HILO, HAWAII (ITO)

The city of Hilo is located near the midpoint of the eastern shore of the Island of Hawaii. This island is by far the largest of the Hawaiian group, with an area of 4,038 square miles, more than twice that of all the other islands combined. Its topography is dominated by the great volcanic masses of Mauna Loa (13,653 feet), Mauna Kea (13,796 feet), and of Haulalai, the Kohala Mountains, and Kilauea. In fact, the island consists entirely of the slopes of these mountains and of the broad saddles between them. Mauna Loa and Kilauea, which occupy the southern half of the island, are still active volcanoes.

Hawaii lies well within the belt of northeasterly trade winds generated by the semi–permanent Pacific high pressure cell to the north and east. The climate provides equable temperatures from day to day and season to season. In Hilo, July and August are the warmest months, with average daily highs and lows of 83 and 68 degrees. January and February, the coolest months, have highs of 80 degrees and lows of 63 degrees. Greater variations occur in localities with less rain and cloud, but temperatures in the mid–90s and low 50s are uncommon anywhere on the island near sea level.

Over the windward slopes of Hawaii, rainfall occurs principally as orographic showers within the ascending moist trade winds. Mean annual rainfall, except for the semi–sheltered Hamakua district, increases from 100 inches or more along the coasts to a maximum of over 300 inches at elevations of 2,000 to 3,000 feet, and then declines to about 15 inches at the summits of Mauna Kea and Mauna Loa. Leeward areas are topographically sheltered from the trades and are therefore drier, although sea breezes created by daytime heating of the land move onshore and upslope, causing afternoon and evening cloudiness and showers. The driest locality on the island, and in the State, with an annual rainfall of less than 10 inches, is the coastal strip just leeward of the southern portion of the Kohala Mountains and of the saddle between the Kohalas and Mauna Kea.

Within the city of Hilo, average rainfall varies from about 130 inches a year near the shore to as much as 200 upslope. The wettest part of the island, with a mean annual rainfall exceeding 300 inches, lies about 6 miles upslope from the city limits. Relative humidity at Hilo is in the moderate range, however, due to the natural ventilation provided by the prevailing winds, the weather is seldom oppressive.

The trade winds prevail throughout the year and profoundly influence the climate. The islands entire western coast is sheltered from the trades by high mountains, except that unusually strong trade winds may sweep through the saddle between the Kohala Mountains and Mauna Kea and reach the areas to the lee. But even places exposed to the trades may be affected by local mountain circulations. Except for heavy rain, really severe weather seldom occurs. During the winter, cold fronts or the cyclonic storms of subtropical origin may bring blizzards to the upper slopes of Mauna Loa and Mauna Kea, with snow extending at times to 9,000 feet or below and icing nearer the summit.

Storms crossing the Pacific a thousand miles to the north, low pressure or tropical storms, may generate seas that cause heavy swell and surf.

NORMALS, MEANS, AND EXTREMES

HILO, HI (ITO)

LATITUDE:    LONGITUDE:    ELEVATION (FT):    TIME ZONE:    WBAN: 21504

19 43′ 24″ N  155 03′ 05″ W  GRND:  44  BARO:  47  HAWAII  (UTC + 10)

ELEMENTPORJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECYEAR
TEMPERATURE FNORMAL DAILY MAXIMUM3079.879.879.579.881.282.783.083.683.883.281.480.081.5
MEAN DAILY MAXIMUM5279.479.279.279.780.882.482.883.483.683.080.979.581.2
HIGHEST DAILY MAXIMUM5592929389949089939291929394
YEAR OF OCCURRENCE199719681972197819661969199519501951197919961980MAY 1966
MEAN OF EXTREME MAXS.5285.585.184.483.784.685.585.986.886.887.285.584.585.5
NORMAL DAILY MINIMUM3063.663.664.465.566.567.668.668.968.668.166.864.866.4
MEAN DAILY MINIMUM5263.563.364.265.366.467.668.669.068.567.966.764.666.3
LOWEST DAILY MINIMUM5554535456586062636162585553
YEAR OF OCCURRENCE199519621983194919471946197019551970199919851977FEB 1962
MEAN OF EXTREME MINS.5258.658.059.661.662.664.365.065.364.964.162.459.562.2
NORMAL DRY BULB3071.771.772.072.773.975.275.876.376.275.774.272.474.0
MEAN DRY BULB5271.471.371.772.473.775.075.776.276.175.473.872.173.7
MEAN WET BULB1766.065.766.667.568.770.071.271.871.470.869.867.268.9
MEAN DEW POINT1763.162.663.564.866.167.568.969.569.168.567.764.766.3
NORMAL NO. DAYS WITH:
MAXIMUM 90300.10.1*0.00.1*0.00.10.20.3*0.11.0
MAXIMUM 32300.00.00.00.00.00.00.00.00.00.00.00.00.0
MINIMUM 32300.00.00.00.00.00.00.00.00.00.00.00.00.0
MINIMUM 0300.00.00.00.00.00.00.00.00.00.00.00.00.0
H/CNORMAL HEATING DEG. DAYS300000000000000
NORMAL COOLING DEG. DAYS302081882172312763063353503363322762293284
RHNORMAL (PERCENT)3077767880797780807980807979
HOUR 02 LST3083838588878688878787868586
HOUR 08 LST3078778081797881807979818079
HOUR 14 LST3066656770676568686970706868
HOUR 20 LST3082818283828182828485858483
SPERCENT POSSIBLE SUNSHINE4946464237374441414338333740
W/OMEAN NO. DAYS WITH:
HEAVY FOG (VISBY 1/4 MI)560.00.00.00.00.00.00.00.00.00.00.10.00.1
THUNDERSTORMS560.91.31.51.00.60.10.30.30.51.11.20.99.7
CLOUDINESSMEAN:
SUNRISE-SUNSET (OKTAS)515.05.36.06.46.25.96.15.95.65.75.95.55.8
MIDNIGHT-MIDNIGHT (OKTAS)335.05.25.96.46.26.16.35.95.65.86.05.55.8
MEAN NO. DAYS WITH:
CLEAR516.55.32.71.21.21.71.31.82.92.73.25.035.5
PARTLY CLOUDY5111.410.310.29.210.611.311.512.212.011.810.010.8131.3
CLOUDY5113.112.718.019.719.117.117.716.514.516.116.214.6195.3
PRMEAN STATION PRESSURE (IN)2929.9629.9830.0230.0230.0230.0129.9929.9729.9429.9529.9629.9729.98
MEAN SEA-LEVEL PRES. (IN)1830.0230.0330.0530.0730.0530.0530.0230.0029.9729.9830.0030.0230.02
WINDSMEAN SPEED (MPH)357.67.98.07.87.67.37.27.27.17.07.07.37.4
PREVAIL. DIR (TENS OF DEGS)2222222222222323232222222222
MAXIMUM 2-MINUTE:
SPEED (MPH)429312623232421242224242531
DIR. (TENS OF DEGS)01350808080607100802040735
YEAR OF OCCURRENCE199819982001200119992001200019981998200119992001FEB 1998
MAXIMUM 5-SECOND:
SPEED (MPH)435382932292825322531293238
DIR. (TENS OF DEGS)36340808110608100803040834
YEAR OF OCCURRENCE199819982001200119992001199819981998200119992001FEB 1998
PRECIPITATIONNORMAL (IN)309.8810.2913.9215.269.916.209.719.348.539.6014.5112.04129.19
MAXIMUM MONTHLY (IN)5932.2445.5549.9343.2425.0122.7028.5926.9221.8226.1045.9050.8250.82
YEAR OF OCCURRENCE197919791980198619641997198219911994195120001954DEC 1954
MINIMUM MONTHLY (IN)590.130.520.882.931.181.803.542.661.592.401.010.280.13
YEAR OF OCCURRENCE199820001972196219451985199919711974196219891980JAN 1998
MAXIMUM IN 24 HOURS (IN)5910.9022.3017.0511.0710.264.727.1111.579.498.8827.3611.4527.36
YEAR OF OCCURRENCE199019791980197119651997198219911994195120001987NOV 2000
NORMAL NO. DAYS WITH:
PRECIPITATION 0.013016.416.623.125.125.524.327.225.923.423.622.419.8273.3
PRECIPITATION 1.00302.62.63.73.72.21.01.71.42.22.23.93.130.3
SNOWFALLNORMAL (IN)300.00.00.00.00.00.00.00.00.00.00.00.00.0
MAXIMUM MONTHLY (IN)10.00.00.00.00.00.00.00.00.00.00.00.00.0
YEAR OF OCCURRENCE
MAXIMUM IN 24 HOURS (IN)550.00.00.00.00.00.00.00.00.00.00.00.00.0
YEAR OF OCCURRENCE
MAXIMUM SNOW DEPTH (IN)470000000000000
YEAR OF OCCURRENCE
NORMAL NO. DAYS WITH:
SNOWFALL 1.0300.00.00.00.00.00.00.00.00.00.00.00.00.0
PRECIPITATION (inches) 2001 HILO, HI (ITO)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
197210.9610.130.8817.794.714.589.078.775.209.5213.234.0198.85
19733.455.5118.847.348.343.694.403.548.079.7226.888.19107.97
19745.887.5713.4719.118.074.767.814.251.596.6514.5619.20112.92
197519.629.2810.4010.233.014.203.838.132.738.8811.158.4799.93
197615.6211.6325.0011.586.012.975.465.135.3111.357.247.37114.67
19771.229.5615.4910.9010.862.466.367.604.1910.308.782.6690.38
19785.414.2612.956.539.6410.9911.1913.535.4410.1220.218.82119.09
197932.2445.555.329.904.1010.456.547.043.645.0321.567.40158.77
19800.914.1449.9311.015.889.669.178.2413.707.697.130.28127.74
19811.514.955.664.634.162.434.328.9712.7910.2311.7318.5389.91
198213.581.3548.5012.006.896.0328.5925.459.926.534.746.78170.36
19830.900.831.9810.319.603.947.217.4812.088.062.333.3768.09
198410.7610.063.3712.086.594.286.639.364.052.5218.3812.00100.08
19852.2516.1421.2810.6117.041.809.866.7111.788.194.712.59112.96
19864.950.5815.3743.248.619.1111.1710.6414.3611.5335.725.75171.03
19879.025.064.799.2415.6512.9118.263.6911.5614.2115.8322.19142.41
198810.319.9513.0912.907.775.115.5016.5611.308.5025.7413.46140.19
198927.466.547.3337.1919.807.0322.938.829.7313.161.015.71166.71
199029.1315.2410.804.028.1310.0410.787.8018.4720.9645.7530.10211.22
19913.819.3237.8811.028.089.859.8226.929.415.156.7415.04153.04
19921.331.293.906.622.999.3617.6313.6217.593.3825.1617.02119.89
19932.172.6711.969.047.546.6318.4311.384.9912.8310.7416.11114.49
199410.3925.5218.488.597.1813.2911.7114.5821.828.7335.916.61182.81
19954.521.564.178.148.685.3515.1313.934.207.628.524.1085.92
199614.2911.8116.666.273.6510.3313.224.777.0311.0714.226.89120.21
19972.337.8419.256.0310.7522.7019.384.758.9812.648.868.10131.61
19980.132.403.678.8615.6511.276.098.4810.7616.0115.579.89108.78
199916.6819.3412.1316.042.844.663.5410.145.653.617.7414.41116.78
200017.870.525.817.253.368.1913.1610.549.2017.6545.904.59144.04
20012.2812.478.3512.562.943.646.547.909.0113.1619.8913.77112.51
POR=59 YRS9.4811.1813.4612.758.846.8910.1310.158.1510.0715.3813.20129.68
AVERAGE TEMPERATURE (F) HILO, HI (ITO)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
197270.170.773.872.773.075.375.476.576.476.073.371.473.7
197372.271.172.572.272.974.675.776.376.375.875.473.874.1
197474.572.673.173.573.875.376.176.977.376.973.672.374.7
197571.071.971.272.473.174.474.875.775.574.773.572.273.4
197671.371.271.672.173.073.674.576.276.976.274.573.273.7
197773.974.073.374.274.776.277.178.177.576.975.273.775.4
197871.772.073.274.276.276.577.176.876.275.574.171.174.6
197969.870.471.573.873.874.274.675.676.576.173.072.873.5
198071.672.672.374.577.377.677.875.075.774.873.874.274.8
198173.572.771.672.874.276.076.176.176.274.673.972.074.1
198271.971.870.371.272.976.376.776.976.174.974.671.873.8
198371.471.972.571.972.674.374.875.274.974.173.872.973.4
198472.471.573.873.074.074.775.275.375.476.573.671.173.9
198569.870.569.469.871.474.475.475.775.774.373.071.672.6
198671.173.674.773.675.476.677.878.577.976.475.172.875.3
198771.870.771.672.272.575.476.777.977.876.674.773.174.3
198871.972.372.272.674.274.775.776.076.677.976.374.974.6
198972.271.472.471.172.774.775.275.074.675.673.671.373.3
199072.170.471.273.574.175.076.077.077.276.275.472.574.2
199172.072.870.872.674.274.876.076.976.976.275.872.974.3
199271.271.472.372.474.876.276.277.277.877.775.273.674.7
199371.170.171.673.573.375.475.877.077.176.073.471.773.8
199470.071.371.773.474.976.078.178.678.177.474.973.074.8
199572.672.974.874.175.576.977.977.778.276.275.674.675.6
199673.470.971.574.476.176.977.577.577.577.375.873.275.2
199773.172.773.374.075.076.777.478.077.776.874.372.475.1
199871.871.772.971.872.273.874.876.174.574.272.469.973.0
199969.769.070.571.172.973.474.374.374.074.072.471.372.2
200069.171.371.871.373.975.575.576.175.475.373.071.773.3
200171.671.071.271.572.373.975.476.176.275.174.072.773.4
POR=55 YRS71.371.271.572.373.574.975.576.175.975.473.872.073.6

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 HILO, HI (ITO)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1983-840000000000000
1984-850000000000000
1985-860000000000000
1986-870000000000000
1987-880000000000000
1988-890000000000000
1989-900000000000000
1990-910000000000000
1991-920000000000000
1992-930000000000000
1993-940000000000000
1994-950000000000000
1995-960000000000000
1996-970000000000000
1997-980000000000000
1998-990000000000000
1999-000000000000000
2000-010000000000000
2001-0000
COOLING DEGREE DAYS (base 65 F) 2001 HILO, HI (ITO)
YEARJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECANNUAL
19721631712812362563163303653493482562073278
19732331802392222532943413583453403212783404
19742992192612632763153513753753762622353607
19751922011972322572883113393233092622333144
19762011862142222552683023553643572912613276
19772802602642813073433794153823743122743871
19782162152632833533513833753413322791953586
19791551602102712782803023383513502462483189
19802132272342933903854053163283132692953668
19812712202102422933383503483453022742253418
19822201961701942523483693793403172932193297
19832072002392142402873133243032882722503137
19842361942822472842983243263203632611953330
19851541611421522042903293393292942482112853
19861962463082643293564044233963633092503844
19872181632122262413193694073893652992593467
19882212162332382932983383493534053453153604
19892271882381892482973273152943352642023124
19902271572002602903083493793763533172373453
19912232221882342963013483783653513332513490
19921971922352293123433553843874023152753626
19931931482132632633183433803703502602173318
19941611832142613123384124274013893052543657
19952412283102813353644104024013553253033955
19962661782092913493603963943793873312653805
19972612212612773173583884073893732872393778
19982161942532112302693113512932892281623007
19991491171791892522572922962782842282002721
20001331912211942803223323503173282472133128
20012091742012042342763303503413192782463162
SNOWFALL (inches) 2001 HILO, HI (ITO)
YEARJULAUGSEPOCTNOVDECJANFEBMARAPRMAYJUNTOTAL
1972-730.00.00.00.00.00.00.00.00.00.00.00.00.0
1973-740.00.00.00.00.00.00.00.00.00.00.00.00.0
1974-750.00.00.00.00.00.00.00.00.00.00.00.00.0
1975-760.00.00.00.00.00.00.00.00.00.00.00.00.0
1976-770.00.00.00.00.00.00.00.00.00.00.00.00.0
1977-780.00.00.00.00.00.00.00.00.00.00.00.00.0
1978-790.00.00.00.00.00.00.00.00.00.00.00.00.0
1979-800.00.00.00.00.00.00.00.00.00.00.00.00.0
1980-810.00.00.00.00.00.00.00.00.00.00.00.00.0
1981-820.00.00.00.00.00.00.00.00.00.00.00.00.0
1982-830.00.00.00.00.00.00.00.00.00.00.00.00.0
1983-840.00.00.00.00.00.00.00.00.00.00.00.00.0
1984-850.00.00.00.00.00.00.00.00.00.00.00.00.0
1985-860.00.00.00.00.00.00.00.00.00.00.00.00.0
1986-870.00.00.00.00.00.00.00.00.00.00.00.00.0
1987-880.00.00.00.00.00.00.00.00.00.00.00.00.0
1988-890.00.00.00.00.00.00.00.00.00.00.00.00.0
1989-900.00.00.00.00.00.00.00.00.00.00.00.00.0
1990-910.00.00.00.00.00.00.00.00.00.00.00.00.0
1991-920.00.00.00.00.00.00.00.00.00.00.00.00.0
1992-930.00.00.00.00.00.00.00.00.00.00.00.00.0
1993-940.00.00.00.00.00.00.00.00.00.00.00.00.0
1994-950.00.00.00.00.00.00.00.00.00.00.00.00.0
1995-960.00.00.00.00.00.00.00.00.00.00.00.00.0
1996-970.00.00.00.00.00.00.00.00.00.00.00.00.0
1997-980.00.00.00.00.00.0
1998-99
1999-00
2000-01
2001-
POR=54 YRS0.00.00.00.00.00.00.00.00.00.00.00.00.0

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