Tuesday, December 29, 2020

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

TUESDAY, DECEMBER 29, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

A WINDY, BUT BRIGHT AND BRILLIANT WINTER DAY
ATOP GREAT BLUE HILL…

Yesterday’s cloudiness departed in the evening hours
in the wake of a mute, passing cold front. Bright
moonlit skies were present throughout the night. Winds
shifted from the south-southwest to more west-northwest
around midnight. This cold air advection has capped any
significant diurnal temperature increase even under today’s
abundant sunshine. For perspective, the 7AM air temperature
was 30F, yet by 1PM we have only reached 36F and now resting
at 33F.

The other story is the dew point and wind. Northwest
winds have really picked-up since midday. Peak gust so far
is 48 MPH! In response, dew points have taken a tumble –
from the upper-teens at sunrise to now in the mid-single
digits.

Visibility has considerably improved since yesterday.
We can clearly see the summit rocks of Mt. Monadnock in
southwestern New Hampshire…an increase of 50 miles!

The high so far today is 38 degrees (set at midnight),
which is 2 degrees above the daily normal high
of 36. The low since midnight is 30F, 10 degrees above
the daily normal low of 20F.

Today’s Observations:

7 A.M.
Weather: Clear (few cumulus NW to SE, Few Altocumulus distant SE to NW)
Temperature: 30F; Dew Point: 19F; Relative Humidity: 63%
Wind: WNW @ 12G22kts
Sea-level pressure: 30.16 in Hg; rising, then rising more slowly
Visibility: 75 miles
6-hr Max temp: 37F
6-hr Min temp: 30F
24-hr Precip: 0.0 ins.
24-hr Snow: 0.0 ins.
Snow Depth: 0 ins.
BHO SA 1155 CLR 75 212/30/19/2912G22/016/ FEW CU NW-SE FEW AC DSNT SE-NW/ 8/130 51025 10037 20030

10 A.M.
Weather: Clear (few Altocumulus distant SW to NW)
Temperature: 34F; Dew Point: 14F; Relative Humidity: 44%
Wind: WNW @ 15G24 kts,
Sea-level pressure: 30.22 in Hg; rising, then rising more slowly
Visibility: 80 miles
3-hr Precip: 0.00 ins.
3-hr Snow: 0.0 ins.
BHO SA 1455 040 SCT 80 234/34/14/3015G24/022/ FEW AC DSNT SW-NW/ 8/130 51022

1 P.M.
Weather: Scattered Cumulus
Temperature: 34F, Dew point: 7F; Relative Humidity: 32%
Wind: WNW @ 16G34 kts,
Peak Wind: 48 MPH WNW @ 11:18 A.M.
Sea-level pressure: 30.23 inches Hg, rising, then rising more rapidly
Visibility: 85 miles
6-hr Max temp: 36F
6-hr Min temp: 30F
Snow Depth: 0 ins.
BHO SA 1755 060 SCT 85 237/34/7/2916G34/023/ PK WND 3042/1618/ 8/100 53003 10036 20030

SUMMARY FOR MONDAY, DECEMBER 28, 2020

TEMPERATURE (DEGREES F)
MAX…….49   NORMAL…..36
MIN…….27   NORMAL…..20
MEAN……38   NORMAL…..28

DEPARTURE FROM 30-YEAR NORMAL…………………+10
TOTAL DEPARTURE FOR THE MONTH…………………+70 [+2.3 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………27  DEPARTURE……-10
TOTAL HEATING UNITS FOR THE MONTH…………..857  DEPARTURE……-73
TOTAL HEATING UNITS FOR THE SEASON…………1830  DEPARTURE…..-361
TOTAL HEATING UNITS LAST SEASON TO DATE…….2161  DEPARTURE…..-331

PEAK WIND GUST FOR YESTERDAY (MPH):
420C/Official…………..35 SSW @ 2:16 P.M.
AEROVANE (south tower)…..36
ASOS…………………..33 S   @ 2:17 P.M.
DAVIS #1……………….35 N   @ 2:16 P.M.
DAVIS #2 (south tower)…..33 SSW @ 2:16 P.M.
RMY……………………37     @ 2:15 P.M.
VECTOR…………………38     @ 2:16 P.M.
MERLIN…………………35

FASTEST MILE FOR YESTERDAY:
CONTACTING/OFFICIAL………………………..25 SSW @ 2:32 P.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….24 S   @ 2:14 P.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………25 W   @ 2:17 P.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………25 SSW @ 2:32 P.M.
MAXIMUM 2-MINUTE RMY AVERAGE………………..25     @ 2:38 P.M.
MAXIMUM 2-MINUTE VECTOR AVERAGE……………..25 SSW @ 2:32 P.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL…13.3 SSW [320 total miles] ASOS………………13.7     [329 total miles] DAVIS #1…………..13.5 SSW [324 total miles] DAVIS #2…………..14.6 S   [350 total miles] RMY……………….13.6 SSW [326 total miles] VECTOR…………….14.0     [336 total miles]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M……TRACE  DEPARTURE….-0.14
ASOS………….0.00
TOTAL PRECIPITATION FOR THE MONTH………….7.18  DEPARTURE….+2.71
ASOS………….7.77
TOTAL PRECIPITATION FOR THE YEAR………….53.58  DEPARTURE….+0.58
ASOS………..55.10

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…..+7.9
TOTAL SNOWFALL FOR THE SEASON……………..26.2  DEPARTURE….+11.8

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   34/29/32/+2/0.00/0.0/…/..       22 WNW  AERO 24 WNW  RMY 23
12/22   42/30/36/+7/0.00/0.0/…/…      34 WNW  AERO 35 WNW  RMY 38
12/23   37/26/32/+3/0.00/0.0/…/..       30 WNW  AERO 28 WNW  RMY 31
12/24   53/30/42/+13/…./…/…/..      46 SSE  AERO 50 SSE  RMY 55
12/25   61/37/49/+21/…./…/…/..      68 SSE  AERO 77 SSE  RMY 84
12/26   37/25/31/+3/0.00/0.0/…/..       38 SW   AERO 44 SW   RMY 43
12/27   38/22/30/+2/0.00/0.0/../..        18 W    AERO 18 W    RMY 20
12/28   49/27/38/+10/T/0.0/../..          35 SSW  AERO 36 –    RMY 37

12/29 The low since midnight is 30F, the daily normal low is 20F

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 29
HIGH 72 IN 1984
LOW -19 IN 1933 (RECORD FOR DECEMBER)
PRECIP 1.91 INS. IN 1945
SNOWFALL 18.4 INS. IN 1945
PEAK GUST 95 MPH S IN 1966 (RECORD FOR DECEMBER)

RECORDS FOR DECEMBER 30
HIGH 60 IN 1984
LOW -18 IN 1933
PRECIP 1.48 INS. IN 1891
SNOWFALL 7.5 INS. IN 1956
PEAK GUST 81 MPH WNW IN 1962

TODAY’S REPORT PREPARED BY: Andrew Swanson