Friday, December 18, 2020

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

FRIDAY, DECEMBER 18, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

COLD AND OVERCAST FOLLOWING YESTERDAY’S NOTABLE
SNOW EVENT….

Final measurement from yesterday’s storm is 16.5
inches with a snow-water equivalent (SWE) of 1.72
inches. This sets a new daily snowfall record of 15.1
inches for December 17th (see more stats below). The
busy east-northeast winds during the storm peaked at 55
MPH which actually disrupted the development of large,
healthy dendrites thus resulting in a meager water to
snow ratio of ~10:1 despite temps well below freezing.
To our distant northwest however, a different story
unfolded. Parts of central New York state, Vermont and
New Hampshire all recorded incredible 40+ inches of
snowfall. There, winds were calmer and air temperatures
much colder than here locally resulting in very impressive
snow ratios.

With the recording of yesterday’s precipitation, we have
officially climbed out of the annual drought. We now stand
with a surplus of +0.11 inches!

Today, skies are overcast with winds on the lighter
side. There is a sharp clearing line invading from the
northwest which will likely deliver us some sunshine before
sunset. Visibility has been exceptional – near perfect
with Mount Monadnock in very clear sight.

The high so far today is 26F, 12 degrees below the
daily normal high of 38F. The low since midnight is
20F, 3 degrees below the normal low of 23F.

BHO GREATEST DECEMBER SNOWSTORMS, inches (1886-2020):
1) 24.3 on   5-7 Dec 2003
2) 21.0 on 11-12 Dec 1960
3) 19.9 on 19-20 Dec 1945
4) 19.0 on   5-6 Dec 1981
5) 18.8 on 29-30 Dec 1945
6) 18.0 on 25-26 Dec 1909
7) 17.5 on 23-24 Dec 1947
8) 16.9 on 26-27 Dec 2010
9) 16.8 on 23-25 Dec 1961
10) 16.5 on 16-17 Dec 2020

BHO GREATEST DECEMBER CALENDAR DAY SNOWFALLS, inches (1886-2020):
1) 20.3 on 12 Dec 1960
2) 18.4 on 29 Dec 1945
3) 17.5 on 26 Dec 1909
4) 17.0 on  6 Dec 2003
5) 15.1 on 17 Dec 2020
6) 15.0 on 12 Dec 1992
7) 14.1 on 19 Dec 1945
8) 13.7 on 20 Dec 2009
9) 13.3 on 26 Dec 2010
10) 13.1 on 29 Dec, 1976

Statistics Provided By: Mike Iacono (BHO Chief Scientist)
———————————————————–

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: Overcast Stratus (few breaks along the NW-N horizon,
virga ESE-SSE)
Temperature: 21F; Dew Point: 16F; Relative Humidity: 81%
Wind: N @ 10 kts
Sea-level pressure: 30.17 in Hg; rising, then rising more rapidly
Visibility: 80 miles (20 miles ESE-SSE)
6-hr Max temp: 21F
6-hr Min temp: 20F
24-hr Precip: 0.59 ins.
24-hr Snow: 7.1 ins.
Snow Depth: 10 ins.
BHO SA 1155 E24 OVC 80 216/21/16/3510/017/ FEW BINOVC ALNG
HRZN DSNT NW-N VSBY 20 ESE-SSE VIRGA ESE-SSE TOTAL NEW SNW
PST 24 HRS 7.1 INS STORM TOTAL 16.5 INS/ 8/6// 4/010 53013
70059 10021 20020

10 A.M.
Weather: Overcast Stratus (few breaks along the NW-N horizon)
Temperature: 24F; Dew Point: 16F; Relative Humidity: 72%
Wind: NNW @ 8G15 kts
Sea-level pressure: 30.22 in Hg; rising, then rising more rapidly
Visibility: 85 miles (25 miles ESE-SSE)
3-hr Precip: 0.00 ins.
3-hr Snow: 0.0 ins.
BHO SA 1455 E45 OVC 85 232/24/16/3408G15/022/ FEW BINOVC
ALNG HRZN DSNT NW-N VSBY 25 ESE-SSE/ 8/6// 53016

1 P.M.
Weather: Broken Stratocumulus (clear sky band in the distant vicinity
extending SSW-NE)
Temperature: 25F; Dew Point: 14F; Relative Humidity: 62%
Wind: NNW @ 9kts
Sea-level pressure: 30.20 in Hg; falling, then rising
Visibility: 85 miles
6-hr Max temp: 26F
6-hr Min temp: 21F
6-hr Precip: 0.00 ins.
6-hr Snow: 0.0 ins.
Snow Depth: 10 ins.
BHO SA 1755 E65 BKN 85 227/25/14/3409/020/ CLR SKY BND
DSNT VC XTDNG SSW-NE/ 8/400 4/010 55005 10026 20021

SUMMARY FOR THURSDAY, DECEMBER 17, 2020

TEMPERATURE (DEGREES F)
MAX…….31   NORMAL…..39
MIN…….19   NORMAL…..23
MEAN……25   NORMAL…..31

DEPARTURE FROM 30-YEAR NORMAL…………………-6
TOTAL DEPARTURE FOR THE MONTH………………..+26 [+1.3 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………40  DEPARTURE…….+6
TOTAL HEATING UNITS FOR THE MONTH…………..506  DEPARTURE……-27
TOTAL HEATING UNITS FOR THE SEASON…………1479  DEPARTURE…..-316
TOTAL HEATING UNITS LAST SEASON TO DATE…….1790  DEPARTURE…..-311

PEAK WIND GUST FOR YESTERDAY (MPH):
420C/Official…………..55 ENE @ 5:45 A.M.
AEROVANE (south tower)…..56 ENE @ 4:05 A.M.
ASOS…………………..55 ENE @ 3:59 A.M.
DAVIS #1……………….54 E   @ 3:59 A.M.
DAVIS #2 (south tower)…..55 ENE @ 5:44 A.M.
RMY……………………59
VECTOR…………………58
MERLIN…………………N/A

FASTEST MILE FOR YESTERDAY:
CONTACTING/OFFICIAL………………………..38 ENE @ 4:05 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….36 ENE @ 4:05 A.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………38 E   @ 4:05 A.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………36 ENE @ 4:05 A.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL….20.3 N  [487 total miles] ASOS……………….19.9    [478 total miles] DAVIS #1……………20.0 NE [480 total miles] DAVIS #2……………19.9 NE [478 total miles] RMY………………..18.9    [454 total miles] VECTOR……………..19.4    [466 total miles]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M…….0.59  DEPARTURE….+0.43
ASOS………….0.72
TOTAL PRECIPITATION FOR THE MONTH………….5.01  DEPARTURE….+2.24
ASOS………….5.51
TOTAL PRECIPITATION FOR THE YEAR………….51.41  DEPARTURE….+0.11
ASOS………..52.84

SNOWFALL (INCHES) THROUGH THIS MORNING (EST):
TOTAL SNOWFALL 24 HOURS ENDING 7 A.M………..7.1  DEPARTURE…..+6.7
TOTAL SNOWFALL FOR THE MONTH………………19.7  DEPARTURE….+13.4
TOTAL SNOWFALL FOR THE SEASON……………..26.2  DEPARTURE….+17.3

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   31/19/25/-6/…./15.1/…/..      55 ENE  AERO 56 ENE  RMY 59

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

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 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

RECORDS FOR DECEMBER 19
HIGH 59 IN 1899
LOW -1 IN 1919
PRECIP 2.06 INS. IN 1986
SNOWFALL 14.1 INS. IN 1945
PEAK GUST 68 NE IN 1986

TODAY’S REPORT PREPARED BY: Andrew Swanson