Tuesday, December 15, 2020

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

TUESDAY, DECEMBER 15, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

SUNSHINE RETURNS, BUT WINDY AND COLD TODAY…

After the rain changed over to snow yesterday afternoon,
we picked up a quick 0.3 ins of accumulation, bringing
the total snow/sleet accumulation to 0.4 ins! 0.10 ins
of liquid was measured for the entire event.

Today bright sunshine has returned, but it’s been what
we call ineffective sunshine. Despite the insolation,
temperatures have been held to the low 30s today thanks
to strong cold air advection taking place.

The dew point has been dropping all day, from 15 degrees
at 7 A.M. to 10 degrees at the 1 P.M. observation. It
has dropped further since then now down in the middle
single digits. This is an indication of an arctic air
mass moving into the region.

In addition to the dropping dew point, winds have been
gusty today, again due to the cold air advection.
Frequent gusts over 25 MPH have been observed today
with a peak thus far to 32 MPH.

The high so far today is 33F, 6 degrees below the
daily normal high of 39F. The low since midnight is
26F, 2 degrees above 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: Clear, few stratocumulus distant NW-NE-SE-SSW,
few cirrus distant S-SW
Temperature: 27F; Dew Point: 15F; Relative Humidity: 60%
Wind: W at 12G18 kts
Sea-level pressure: 30.08 in Hg; rising, then more slowly
Visibility: 50 miles
6-hr Max temp: 30F
6-hr Min temp: 26F
24-hr Precip: 0.10 ins.
24-hr Snow: 0.4 ins.
Snow Depth: Trace.
BHO SA 1155 CLR 50 186/27/15/2812G18/008/ FEW SC DSNT NW-NE-SE-SSW
FEW CI DSNT S-SW TOTAL NEW SNW PST 24 HRS 0.4 INS/ 8/501 4/000
51023 70010 10030 20026

10 A.M.
Weather: Clear, few stratocumulus distant NW-NE-E, few cirrus
SE-SW
Temperature: 30F; Dew Point: 11F; Relative Humidity: 45%
Wind: W at 12G24 kts, peak wind W 32 MPH at 9:31 A.M.
Sea-level pressure: 30.16 in Hg; rising, then more rapidly
Visibility: 70 miles
3-hr Precip: 0.00 ins.
3-hr Snow: 0.0 ins.
BHO SA 1455 CLR 70 213/30/11/2812G24/016/ FEW SC DSNT NW-NE-E
FEW CI SE-SW PK WND 2828/31/ 8/501 53027

1 P.M.
Weather: Thin scattered cirrus, few stratocumulus distant NW-NNW
and distant NNE-ESE
Temperature: 33F; Dew Point: 10F; Relative Humidity: 38%
Wind: WNW at 12G21 kts
Sea-level pressure: 30.16 in Hg; falling, then rising
Visibility: 70 miles
6-hr Max temp: 33F
6-hr Min temp: 26F
6-hr Precip: 0.00 ins.
6-hr Snow: 0.0 ins.
Snow Depth: Trace.
BHO SA 1755 250 -SCT 70 213/33/10/2912G21/016/ FEW SC DSNT NW-NNW
AND DSNT NNE-ESE/ 8/501 4/000 55000 10033 20026

SUMMARY FOR MONDAY, DECEMBER 14, 2020

TEMPERATURE (DEGREES F)
MAX…….35   NORMAL…..40
MIN…….30   NORMAL…..24
MEAN……33   NORMAL…..32

DEPARTURE FROM 30-YEAR NORMAL……………….  +1
TOTAL DEPARTURE FOR THE MONTH………………. +47 [+3.2 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………32  DEPARTURE…… -1
TOTAL HEATING UNITS FOR THE MONTH…………..384  DEPARTURE……-48
TOTAL HEATING UNITS FOR THE SEASON…………1357  DEPARTURE…..-336
TOTAL HEATING UNITS LAST SEASON TO DATE…….1690  DEPARTURE…..-333

PEAK WIND GUST FOR YESTERDAY (MPH):
420C/Official…………..25 N    AT  9:05 A.M.
AEROVANE (south tower)…..25 N    AT  9:05 A.M.
ASOS…………………..26 NNE  AT  9:07 A.M.
DAVIS #1……………….26 N    AT  9:00 A.M.
DAVIS #2 (south tower)…..24 NNE  AT  8:59 A.M.
RMY……………………29
VECTOR…………………28
MERLIN…………………26

FASTEST MILE FOR YESTERDAY:
CONTACTING/OFFICIAL………………………..18 N   AT   9:00 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….18 N   AT   9:00 A.M.
MAXIMUM 2-MINUTE DAVIS #1 AVERAGE……………18 N   AT   9:00 A.M.
MAXIMUM 2-MINUTE DAVIS #2 AVERAGE……………19 N   AT   9:00 A.M.

AVERAGE WIND SPEED AND DIRECTION:
CONTACTING/OFFICIAL…. 7.5 NW   [179 total miles] ASOS………………. 8.1      [194 total miles] DAVIS #1…………… 8.0 NW   [192 total miles] DAVIS #2…………… 8.2 NW   [197 total miles] RMY……………….. 7.9 NW   [190 total miles] VECTOR…………….. 8.1      [194 total miles]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST):
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M…….0.10  DEPARTURE….-0.06
ASOS………….0.11
TOTAL PRECIPITATION FOR THE MONTH………….3.29  DEPARTURE….+0.99
ASOS………….3.40
TOTAL PRECIPITATION FOR THE YEAR………….49.69  DEPARTURE….-1.14
ASOS………..50.73

SNOWFALL (INCHES) THROUGH THIS MORNING (EST):
TOTAL SNOWFALL 24 HOURS ENDING 7 A.M………..0.4  DEPARTURE….. 0.0
TOTAL SNOWFALL FOR THE MONTH……………….3.2  DEPARTURE…..-1.6
TOTAL SNOWFALL FOR THE SEASON………………9.7  DEPARTURE…..+2.3

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 The low since midnight is 26F, the daily normal low is 24F

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

RECORDS FOR DECEMBER 14
HIGH 62 IN 1901
LOW -6 IN 1893
PRECIP 1.94 INS. IN 2002
SNOWFALL 8.0 INS. IN 1907
PEAK GUST 78e ENE IN 1941

RECORDS FOR DECEMBER 15
HIGH 64 IN 1975
LOW 4 IN 1900, 1905, 1933
PRECIP 1.80 INS. IN 1981
SNOW 7.5 INS. IN 1951
PEAK GUST 65 MPH NW IN 1991

TODAY’S REPORT PREPARED BY: Matt Douglas