Thursday, December 17, 2020

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

THURSDAY, DECEMBER 17, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

FIRST MAJOR SNOW STORM OF THE SEASON ATOP
GREAT BLUE HILL….

Conditions were very snowy starting later on
yesterday night, and 9.4 inches of snow was
measured at 7 A.M. Since then, another 7 inches
fell primarily between the 7 A.M. and 1 P.M.
observations. Light snow has persisted since
then, but is not accumulating. The sun is
breaking through at times, and the storm has
mostly moved offshore.

Liquid amounts from this storm totaled 1.69
inches! The snowfall since midnight of at least
15 inches will be a new record for December 17th.

Wind was very significant today, reaching a
peak gust of 53 mph this morning. Average
wind speed was above 20 mph for the whole
storm, with frequent gusts of 30 and even
40 mph at times. We noticed a wind shift
from ENE to NNE this morning. This kept
temperatures well below normal, bringing
in a lot of colder air from the north.

The high so far today is 31F, 8 degrees below the
daily normal high of 39F. The low since midnight is
20F, 4 degrees below the normal low of 24F.
PRELIMINARY STATS FOR NOVEMBER 2020

TEMPERATURE, Deg. F
Avg. Max. 56.3 [+6.3] Avg. Min. 38.6 [+5.1] Mean      47.5 [+5.8] 24-hour corrected mean: 46.9
Max. for month: 75F on the 7th
Min. for month: 18F on the 19th

HEATING DEGREE DAYS
Total heating units:   521 [-177] Total for the season:  973 [-288] Total for last season: 1237

PRECIPITATION, Inches
Total: 5.23 [+1.77] Greatest in 24 hrs: 1.77 ins. on the 23rd

SNOWFALL, Inches
Total: TRACE
Greatest in 24 hrs: T on the 2nd

WIND, mph
Avg. uncorrected wind speed: 12.9 mph
Avg. corrected wind speed:   13.2 mph
Prevailing wind direction:   SSW [14%] Peak gust and direction:     81 SSE on the 30th

SUNSHINE:
Campbell-Stokes card minutes: 9066 minutes of a possible 17010 or 53%
Astronomical total minutes: 9382 minutes of a possible 17593 or 53%

Today’s Observations:

7 A.M.
Weather: Heavy snow
Temperature: 31F; Dew Point: 31F; Relative Humidity: 100%
Wind: NE at 26G43 kts, peak of 53 mph ENE at 6:38 A.M.
Sea-level pressure: 29.84 in Hg; falling then rising
Visibility: 1/4 mile, fog and blowing snow
6-hr Max temp: 31F
6-hr Min temp: 27F
24-hr Precip: 1.13 ins.
24-hr Snow: 9.4 ins.
Snow Depth: 9 ins.
BHO SA 1155 X W2 1/4S+BSF 104/31/31/0526G43/984/ DRFTG SNW
PK WND 0746/38 TOTAL NEW SNW PST 24 HRS 9.4 INS/ 8//// 4/009
50001 6//// 70113 10031 20027

10 A.M.
Weather: Snow
Temperature: 22F; Dew Point: 22F; Relative Humidity: 100%
Wind: N at 21G32 kts, peak of 51 mph NNE at 9:08 A.M.
Sea-level pressure: 29.86 in Hg; falling then rising
Visibility: 3/4 mile, fog and blowing snow
3-hr Precip: 0.44 ins.
3-hr Snow: 4.3 ins.
BHO SA 1455 X W2 3/4SBSF 112/22/22/0121G32/986/ DRFTG SNW
PK WND 0244/08/ TOTAL NEW SNW PST 3 HRS 4.3 INS/ 8//// 53008
6044/

1 P.M.
Weather: Broken stratus fractus, overcast nimbostratus,
sun occasionally dimly visible, light snow
Temperature: 20F; Dew Point: 20F; Relative Humidity: 100%
Wind: N at 18G28 kts, peak of 35 mph N at 11:58 A.M.
Sea-level pressure: 29.85 in Hg; falling, then rising
Visibility: 1 and 1/2 miles, fog and blowing snow
6-hr Max temp: 31F
6-hr Min temp: 20F
6-hr Precip: 0.56 ins.
6-hr Snow: 7.0 ins.
Snow Depth: 14 ins.
BHO SA 1755 E13 BKN 20 OVC 11/2S-BSF 108/20/20/3518G28/985/ SUN OCLY DMLY VSBL PK WND 3530/1658/ TOTAL NEW SNW PST 6 HRS 7.0 INS/ 8/6// 4/014 56004 6056/ 10031 20020

SUMMARY FOR WEDNESDAY, DECEMBER 16, 2020

TEMPERATURE (DEGREES F)
MAX…….27   NORMAL…..39
MIN…….13   NORMAL…..24
MEAN……20   NORMAL…..31

DEPARTURE FROM 30-YEAR NORMAL………………. -11
TOTAL DEPARTURE FOR THE MONTH………………. +32 [+1.8 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………45  DEPARTURE……+11
TOTAL HEATING UNITS FOR THE MONTH…………..466  DEPARTURE……-33
TOTAL HEATING UNITS FOR THE SEASON…………1439  DEPARTURE…..-322
TOTAL HEATING UNITS LAST SEASON TO DATE…….1754  DEPARTURE…..-315

PEAK WIND GUST FOR YESTERDAY (MPH):
420C/Official…………..38 E    AT 11:30 P.M.
AEROVANE (south tower)…..37 E    AT 11:28 P.M.
ASOS…………………..38 E    AT 11:31 P.M.
DAVIS #1……………….36 E    AT 11:30 P.M.
DAVIS #2 (south tower)…..36 E    AT 11:33 P.M.
RMY……………………39
VECTOR…………………40
MERLIN…………………N/A

FASTEST MILE FOR YESTERDAY:
CONTACTING/OFFICIAL………………………..25 E   AT  11:36 P.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….25 E   AT  11:34 P.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………27 E   AT  11:33 P.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………26 E   AT  11:39 P.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL…..9.8 NNW  [234 total miles] ASOS……………….10.4      [250 total miles] DAVIS #1……………10.3 NE   [247 total miles] DAVIS #2……………10.3 NE   [247 total miles] RMY…………………9.6 ENE  [229 total miles] VECTOR……………..10.1      [234 total miles]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M…….1.13  DEPARTURE….+0.98
ASOS………….1.39
TOTAL PRECIPITATION FOR THE MONTH………….4.42  DEPARTURE….+0.83
ASOS………….4.79
TOTAL PRECIPITATION FOR THE YEAR………….50.82  DEPARTURE….-1.30
ASOS………..52.12

SNOWFALL (INCHES) THROUGH THIS MORNING (EST):
TOTAL SNOWFALL 24 HOURS ENDING 7 A.M………..9.4  DEPARTURE…..+8.9
TOTAL SNOWFALL FOR THE MONTH……………….3.2  DEPARTURE…..+6.8
TOTAL SNOWFALL FOR THE SEASON………………9.7  DEPARTURE….+10.7

PRELIMINARY CLIMATE SUMMARY FOR NOVEMBER 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

11/01   49/36/43/-3/0.69/0.0/006/01      38 W     AERO 40 W    RMY 39
11/02   40/31/36/-10/T/T/425/69          61 WNW   AERO 62 WNW  RMY 62
11/03   43/29/36/-10/0.00/0.0/473/77     48 WNW   AERO 53 WNW  RMY 48
11/04   54/30/42/-3/0.00/0.0/550/90      30 SSW   AERO 30 SSW  RMY 30
11/05   69/49/59/+14/0.00/0.0/548/90     37 SSW   AERO 40 SSW  RMY 38
11/06   72/55/64/+19/0.00/0.0/394/65     28 SW    AERO 28 SW   RMY M
11/07   75/54/65/+20/0.00/0.0/562/93     21 WSW   AERO 21 WSW  RMY 21
11/08   73/54/64/+20/0.00/0.0/584/97     18 W     AERO 18 W    RMY 19
11/09   74/52/63/+19/0.00/0.0/593/99     20 WSW   AERO 18 WSW  RMY 21
11/10   74/53/64/+20/0.00/0.0/597/100    30 SW    AERO 28 SW   RMY 31
11/11   73/58/66/+23/0.04/0.0/137/23     40 SW    AERO 44 SW   RMY 45
11/12   64/46/55/+12/0.04/0.0/000/00     32 NNW   AERO 31 NNW  RMY 33
11/13   48/38/43/0/0.30/0.0/000/00       22 NW    AERO 21 NW   RMY 25
11/14   49/32/41/-1/0.00/0.0/276/47      26 NW    AERO 28 NW   RMY 29
11/15   58/30/44/+2/0.62/0.0/311/53      60 S     AERO 67 S    RMY 65
11/16   53/39/46/+4/0.00/0.0/526/90      40 WNW   AERO 41 WNW  RMY 43
11/17   47/32/40/-1/0.00/0.0/204/35      28 NW    AERO 28 NW   RMY 30
11/18   32/19/26/-15/0.00/0.0/580/100    40 NW    AERO 46 NW   RMY 43
11/19   44/18/31/-10/0.00/0.0/393/68     37 SW    AERO 39 SW   RMY 43
11/20   63/44/54/+14/0.00/0.0/495/86     33 SSW   AERO 35 SSW  RMY 37
11/21   62/40/51/+11/0.00/0.0/339/59     24 W     AERO 23 W    RMY 27
11/22   45/33/39/-1/T/0.0/006/01         28 SE    AERO 28 SE   RMY 31
11/23   58/32/45/+6/1.77/0.0/000/00      42 WNW   AERO 48 WNW  RMY 46 TSTM
11/24   42/27/35/-4/0.00/0.0/569/100     31 WNW   AERO 32 WNW  RMY 33
11/25   50/26/38/-1/0.01/0.0/017/03      23 SSE   AERO 23 SSE  RMY 26
11/26   58/45/52/+14/0.36/0.0/000/00     36 S     AERO 37 S    RMY 41
11/27   53/46/50/+12/0.00/0.0/056/10     23 WNW   AERO 23 WNW  RMY 23
11/28   52/36/44/+6/T/0.0/180/32         28 WNW   AERO 30 WNW  RMY 27
11/29   52/33/43/+6/0.00/0.0/561/100     21 SSW   AERO 21 SSW  RMY 22
11/30   62/40/51/+14/1.35/0.0/000/00     81 SSE   AERO 82 SSE  RMY 86

DAILY RECORDS FOR NOVEMBER 2020

11/06/20: DAILY RECORD HIGH MAXIMUM TEMPERATURE OF 72F,
BREAKS PREVIOUS RECORD OF 71F SET IN 1959 AND 2015

11/07/20: DAILY RECORD HIGH MAXIMUM TEMPERATURE OF 75F,
TIES PREVIOUS RECORD OF 75F SET IN 1938

11/08/20: DAILY RECORD HIGH MAXIMUM TEMPERATURE OF 73F,
BREAKS PREVIOUS RECORD OF 72F SET IN 1938

11/09/20: DAILY RECORD HIGH MAXIMUM TEMPERATURE OF 74F,
BREAKS PREVIOUS RECORD OF 72F SET IN 1975

11/11/20: DAILY RECORD HIGH MINIMUM TEMPERATURE OF 58F,
BREAKS PREVIOUS RECORD OF 56F IN 2002
DAILY RECORD HIGH MAXIMUM TEMPERATURE OF 73F,
BREAKS PREVIOUS RECORD OF 68F IN 1984

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 The low since midnight is 20F, the daily normal low is 23F

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

RECORDS FOR DECEMBER 17
HIGH 63 IN 2000
LOW -10 IN 1942
PRECIP 3.03 INS. IN 1888
SNOWFALL 7.5 INS. IN 1988
PEAK GUST 78 MPH SSE IN 2000

RECORDS FOR DECEMBER 18
HIGH 59 IN 1928
LOW -11 IN 1919
PRECIP 1.44 INS. IN 1915
SNOWFALL 7.0 INS. IN 1904
PEAK GUST 76e W IN 1978

TODAY’S REPORT PREPARED BY: Benjamin Turner