Monday, December 21, 2020

BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA

MONDAY, DECEMBER 21, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

FOGGY WITH A LIGHT NORTHWESTERLY WIND, CLEARING UP
A LITTLE IN THE AFTERNOON….

Today we observed foggy conditions, which limited
visibility to a 1/16th mile. This improved after
noontime, increasing to 5 miles by 2 P.M. Wind was
on the lighter side today, barely reaching 10 mph.
Last night’s precipitation left us a trace of snow
and 0.02 inches of liquid in the gauge at the 7 A.M.
observation.

The high so far today is 33F, 5 degrees below the daily
normal maximum of 38F. The low since midnight is 29F,
7 degrees above the normal minimum of 22F.

Today’s Observations:

7 A.M.
Weather: Fog
Temperature: 31F; Dew Point: 31F; Relative Humidity: 100%
Wind: W @ 5 kts, wind light
Sea-level pressure: 29.89 in Hg; falling unsteadily
Visibility: 1/16th mile, fog
6-hr Max temp: 32F
6-hr Min temp: 29F
24-hr Precip: 0.02 ins.
24-hr Snow: Trace
Snow Depth: 8 ins.
BHO SA 1155 X W3 1/16F 125/31/31/2705/989/ WND LGT NEW SNW
PST 24 HRS TRACE/ 8//// 4/008 70002 56011 10032 20029

10 A.M.
Weather: Fog
Temperature: 31F; Dew Point: 31F; Relative Humidity: 100%
Wind: NW @ 7 kts
Sea-level pressure: 29.84 in Hg; rising, then falling
Visibility: 1/16th mile, fog
3-hr Precip: 0.00 ins.
3-hr Snow: 0.0 ins.
BHO SA 1455 X W3 1/16F 108/31/31/3207/984/ 8//// 56017

1 P.M.
Weather: Overcast stratus
Temperature: 33F; Dew Point: 33F; Relative Humidity: 100%
Wind: NNW @ 5 kts, wind light
Sea-level pressure: 29.75 in Hg; falling, then falling more
quickly
Visibility: 2 miles, fog
6-hr Max temp: 33F
6-hr Min temp: 31F
6-hr Precip: 0.00 ins.
6-hr Snow: 0.0 ins.
Snow Depth: 8 ins.
BHO SA 1755 10 OVC 2F 075/33/33/3405/975/ WND LGT/ 8/6//
4/008 58033 10033 20031

SUMMARY FOR SUNDAY, DECEMBER 20, 2020

TEMPERATURE (DEGREES F)
MAX…….36   NORMAL…..38
MIN…….24   NORMAL…..22
MEAN……30   NORMAL…..30

DEPARTURE FROM 30-YEAR NORMAL…………………0
TOTAL DEPARTURE FOR THE MONTH…………………+9 [+0.3 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………35  DEPARTURE…….+0
TOTAL HEATING UNITS FOR THE MONTH…………..627  DEPARTURE……-11
TOTAL HEATING UNITS FOR THE SEASON…………1600  DEPARTURE…..-300
TOTAL HEATING UNITS LAST SEASON TO DATE…….1924  DEPARTURE…..-324

PEAK WIND GUST FOR YESTERDAY (MPH):
420C/Official…………..14 S   @  7:51 A.M.
AEROVANE (south tower)…..16 SW  @ 12:16 A.M.
ASOS…………………..14 SSW @  6:01 P.M.
DAVIS #1……………….14 SW  @ 12:24 A.M.
DAVIS #2 (south tower)…..15 SW  @ 12:57 A.M.
RMY……………………14
VECTOR…………………15
MERLIN…………………N/A

FASTEST MILE FOR YESTERDAY:
CONTACTING/OFFICIAL………………………..12 SW  @ 12:14 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….12 SW  @  8:53 P.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………12 WSW @ 12:57 A.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………13 SW  @ 12:26 A.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL….7.2 SW  [172 total miles] ASOS……………….7.8     [177 total miles] DAVIS #1……………7.5 SW  [180 total miles] DAVIS #2……………8.3 SW  [188 total miles] RMY………………..7.7 SW  [185 total miles] VECTOR……………..8.2     [186 total miles]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M…….0.02  DEPARTURE….-0.14
ASOS………….0.02
TOTAL PRECIPITATION FOR THE MONTH………….5.03  DEPARTURE….+1.93
ASOS………….5.53
TOTAL PRECIPITATION FOR THE YEAR………….51.43  DEPARTURE….-0.20
ASOS………..52.86

SNOWFALL (INCHES) THROUGH THIS MORNING (EST):
TOTAL SNOWFALL 24 HOURS ENDING 7 A.M………Trace  DEPARTURE…..-0.6
TOTAL SNOWFALL FOR THE MONTH………………19.7  DEPARTURE….+11.9
TOTAL SNOWFALL FOR THE SEASON……………..26.2  DEPARTURE….+15.8

PRELIMINARY CLIMATE SUMMARY FOR DECEMBER CALENDAR DAY DATA
DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN.)/SUN(%)/PEAK GUST/AERO/RMY GUST
AERO: Aerovane wind recording system gust
RMY:  R.M. Young wind gust recording system
TSTM: Thunderstorm day (thunder heard some time during day)
….: Data not yet available, records not finalized
M:    Missing data

12/01   62/40/51/+14/0.61/0.0/…/..      60 S    AERO 67 W    RMY 64
12/02   42/32/37/+1/0.00/0.0/…/..       32 SW   AERO 32 SW   RMY 35
12/03   49/30/40/+4/0.00/0.0/…/..       25 SSW  AERO 25 SSW  RMY 28
12/04   58/40/49/+14/0.06/0.0/…/..      35 SSW  AERO 35 SSW  RMY 37
12/05   42/32/37/+2/2.13/2.8/…/..       58 NNW  AERO 58 NNW  RMY 67
12/06   34/26/30/-5/0.01/T/…/..        E44 WNW  AERO 44 WNW  RMY 49
12/07   33/22/28/-6/T/T/…/..            24 NW   AERO 26 NW   RMY 26
12/08   29/22/26/-8/T/T/…/..            24 NW   AERO 25 NW   RMY 28
12/09   34/19/27/-7/T/T/…/..            16 W    AERO 17 W    RMY 19
12/10   42/30/36/+3/0.00/0.0/…/..       30 WNW  AERO 31 WNW  RMY 29
12/11   50/31/41/+8/0.00/0.0/…/..       32 SW   AERO 35 SW   RMY 34
12/12   48/40/44/+11/0.38/0.0/…/..      25 E    AERO 21 E    RMY 25
12/13   58/35/47/+15/0.00/0.0…/..       28 W    AERO 31 WSW  RMY 31
12/14   35/30/33/+1/0.10/0.4/…/..       25 N    AERO 25 N    RMY 29
12/15   34/21/28/-4/0.00/0.0/…/..       32 WNW  AERO 33 WNW  RMY 38
12/16   27/13/20/-11/…./1.4/…/..      38 E    AERO 37 E    RMY 39
12/17   31/19/25/-6/…./15.1/…/..      55 ENE  AERO 56 ENE  RMY 59
12/18   27/18/23/-8/0.00/0.0/…/..       28 N    AERO 26 N    RMY 27
12/19   29/13/21/-9/0.00/0.0/…/..       16 SW   AERO 16 S    RMY 16
12/20   36/24/30/0/0.02/T/…/..          14 S    AERO 16 SW   RMY 14

12/21   The low since midnight is 29F, the daily normal low is 22F

DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):

RECORDS FOR DECEMBER 21
HIGH 60 IN 1957
LOW -10 IN 1942
PRECIP 2.01 INS. IN 1946
SNOWFALL 11.4 INS. IN 1954
PEAK GUST 77 MPH SSE IN 1957

RECORDS FOR DECEMBER 22
HIGH 63 IN 2013
LOW -5 IN 1921
PRECIP 1.52 INS. IN 1975
SNOWFALL 8.8 INS. IN 1975
PEAK GUST 62 MPH WNW IN 1998

TODAY’S REPORT PREPARED BY: Benjamin Turner