Sunday, December 20, 2020

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

SUNDAY, DECEMBER 20, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

OVERCAST WITH SOME DISTANT SNOW BEING SEEN TO
THE WEST IN THE AFTERNOON HOURS….

Today we observed mostly cloudy to overcast conditions,
along with seasonably cold temperatures. Wind was light
at barely 5 mph at 2 P.M. Visibility has been limited
by a number of factors including haze, smoke, and
even distant snow to the west at the 1 P.M. observation.
We were still able to see a visibility of 60 miles at
10 A.M.

Houghton’s Pond and Lake Ponkapoag are now completely
covered in ice due to well below freezing temperatures
overnight. Mostly cloudy skies today have left us with
the same snow depth we had this morning of 9 inches.

The high so far today is 35F, 3 degrees below the daily
normal maximum of 38F. The low since midnight is 24F, 2
degrees above the normal minimum of 22F.

Today’s Observations:

7 A.M.
Weather: Broken altocumulus and altostratus
Temperature: 26F; Dew Point: 20F; Relative Humidity: 77%
Wind: S @ 8 kts
Sea-level pressure: 30.24 in Hg; falling unsteadily
Visibility: 25 miles, hazy
6-hr Max temp: 26F
6-hr Min temp: 24F
24-hr Precip: 0.00 ins.
24-hr Snow: 0.0 ins.
Snow Depth: 9 ins.
BHO SA 1155 130 BKN 25 241/26/20/1808/024/ HAZY/ 8/070 4/009
56007 10026 20024

10 A.M.
Weather: Broken altocumulus and altostratus
Temperature: 32F; Dew Point: 26F; Relative Humidity: 78%
Wind: SSW @ 7 kts
Sea-level pressure: 30.23 in Hg; rising, then falling
Visibility: 60 miles, thin smoke layer
3-hr Precip: 0.00 ins.
3-hr Snow: 0.0 ins.
BHO SA 1455 130 BKN 60 239/32/26/2007/023/ THN K LYR ALQDS/
8/070 58002

1 P.M.
Weather: Overcast altocumulus and altostratus
Temperature: 35F; Dew Point: 29F; Relative Humidity: 80%
Wind: SSE @ 7 kts
Sea-level pressure: 30.13 in Hg; falling, then falling more quickly
Visibility: 50 miles (30 miles SW-NW due to virga)
6-hr Max temp: 35F
6-hr Min temp: 26F
6-hr Precip: 0.00 ins.
6-hr Snow: 0.0 ins.
Snow Depth: 9 ins.
BHO SA 1755 130 OVC 50 202/35/29/1507/013/ VSBY 30 VIRGA SW-NW/
8/07/ 4/009 56037 10035 20026

SUMMARY FOR SATURDAY, DECEMBER 19, 2020

TEMPERATURE (DEGREES F)
MAX…….29   NORMAL…..38
MIN…….13   NORMAL…..23
MEAN……21   NORMAL…..30

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

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………44  DEPARTURE…….+9
TOTAL HEATING UNITS FOR THE MONTH…………..592  DEPARTURE……-11
TOTAL HEATING UNITS FOR THE SEASON…………1565  DEPARTURE…..-299
TOTAL HEATING UNITS LAST SEASON TO DATE…….1879  DEPARTURE…..-314

PEAK WIND GUST FOR YESTERDAY (MPH):
420C/Official…………..16 SW  @ 10:41 P.M.
AEROVANE (south tower)…..16 S   @  8:51 P.M.
ASOS…………………..16 S   @  8:52 P.M.
DAVIS #1……………….16 N   @ 12:11 A.M.
DAVIS #2 (south tower)…..16 N   @ 12:11 A.M.
RMY……………………17
VECTOR…………………17
MERLIN…………………15

FASTEST MILE FOR YESTERDAY:
CONTACTING/OFFICIAL………………………..14 NNW @ 12:46 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….14 N   @ 12:50 A.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………14 N   @ 12:13 A.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………14 N   @ 12:13 A.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL….6.8 NNW [163 total miles] ASOS……………….7.5     [180 total miles] DAVIS #1……………7.5 WNW [180 total miles] DAVIS #2……………7.9 WNW [183 total miles] RMY………………..7.5 W   [180 total miles] VECTOR……………..8.0     [184 total miles]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M…….0.00  DEPARTURE….-0.15
ASOS………….0.00
TOTAL PRECIPITATION FOR THE MONTH………….5.01  DEPARTURE….+1.93
ASOS………….5.51
TOTAL PRECIPITATION FOR THE YEAR………….51.41  DEPARTURE….-0.20
ASOS………..52.84

SNOWFALL (INCHES) THROUGH THIS MORNING (EST):
TOTAL SNOWFALL 24 HOURS ENDING 7 A.M………..0.0  DEPARTURE…..-0.5
TOTAL SNOWFALL FOR THE MONTH………………19.7  DEPARTURE….+12.5
TOTAL SNOWFALL FOR THE SEASON……………..26.2  DEPARTURE….+16.9

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   The low since midnight is 24F, the daily normal low is 22F

DAILY RECORDS FOR DECEMBER 2020

12/17/20: DAILY RECORD SNOWFALL OF 15.1 INCHES,
BREAKS PREVIOUS RECORD OF 7.5 INCHES SET IN 1988

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

RECORDS FOR DECEMBER 20
HIGH 61 IN 1957
LOW -16 IN 1942
PRECIP 1.69 INS. IN 1936
SNOWFALL 13.7 INS. IN 2009
PEAK GUST 75 MPH S IN 2002

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

TODAY’S REPORT PREPARED BY: Benjamin Turner