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

DAILY DISCUSSION AND CLIMATE SUMMARY
THURSDAY, DECEMBER 21, 2017  
ALL TIMES ARE IN EASTERN STANDARD TIME

NORTHWEST WIND BRINGS COOL DRY AIR TO GREAT
BLUE HILL...TODAY IS THE WINTER SOLSTICE AND THE
SHORTEST DAY OF THE YEAR...

We had a northwest wind today which became light 
in the afternoon. This made for temperatures which
were slightly below seasonable with a high of 31F
so far today. This is 6 degrees below the normal
of 37F. With high pressure in the region the sky 
remained clear for most of the day. With humidity
dropping throughout the day visibility increased
from 60 miles to 80 miles by 10:00 AM.  

Today's Observations:

7 A.M.
Weather: Clear, few cumulus distant along horizon ENE-ESE,
few cirrocumulus in all directions  
Temperature: 24F; Dew Point: 16F; Wind: NW at 10G17 kts
Sea-level pressure: 30.09 ins. Hg, rising, then more quickly 
Visibility: 60 miles, distant haze WSW-WNW
6-hr Max temp: 26F
6-hr Min temp: 23F
24-hr precip: 0.00 ins.
24-hr snowfall: 0.0 ins. 
Snow cover: 0 ins.
BHO SA 1155 CLR 60 191/24/16/3110G17/009/ FEW CU DSNT ALG HRZN 
ENE-ESE FEW CC ALQDS DSNT HZ WSW-WNW/ 8/109 51023 10026 20023 

10 A.M.
Weather: Scattered altocumulus, scattered cirrostatus,
few cumulus distant along horizon ENE-ESE  
Temperature: 27F; Dew Point: 11F; Wind: NW at 11G20 kts
Sea-level pressure: 30.16 ins. Hg, rising, then more slowly 
Visibility: 80 miles
3-hr precip: 0.00 ins. 
3-hr snowfall: 0.0 ins.
BHO SA 1455 120 SCT 200 SCT 80 212/27/11/3211G20/016/ 
FEW CU DSNT ALG HRZN ENE-ESE/ 8/135 52021 

1 P.M.
Weather: Clear, few stratocumulus along the horizon ENE-E
few cirrostratus SSW-N
Temperature: 31F; Dew Point: 9F; Wind: WNW at 5 kts,
Wind: Light
Sea-level pressure: 30.17 ins. Hg, rising then falling 
Visibility: 80 miles
6-hr Max temp: 31F
6-hr Min temp: 24F
6-hr precip: 0.00 ins.
6-hr snowfall: 0.0 ins. 
Snow cover: 0 ins.
BHO SA 1755 CLR 80 216/31/09/2905/017/ FEW SC ENE-E DSNT ALG 
HRZN ENE-E FEW CS SSW-N WND LGT/ 8/105 50002 10031 20024 

SUMMARY FOR WEDNESDAY, DECEMBER 20, 2017

TEMPERATURE (DEGREES F)
MAX.....42   NORMAL.....38
MIN.....26   NORMAL.....22
MEAN....34   NORMAL.....30

DEPARTURE FROM 30-YEAR NORMAL...........................+4
TOTAL DEPARTURE FOR THE MONTH...........................-2 [-0.3 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY.............31  DEPARTURE..........-4
TOTAL HEATING UNITS FOR THE MONTH............639  DEPARTURE..........+1
TOTAL HEATING UNITS FOR THE SEASON..........1608  DEPARTURE........-292
TOTAL HEATING UNITS LAST SEASON TO DATE.....1705  DIFFERENCE........-97

PEAK GUST AND AVERAGE WIND SPEED (MPH) 
PEAK WIND GUST FOR YESTERDAY...................41 W AT 10:58 A.M. 
                   AERO........................40 W AT 10:58 A.M.
                   ASOS........................44 W AT 11:00 A.M.
                   DAVIS.......................41 W AT 10:18 A.M. RMY 45
FASTEST MILE FOR YESTERDAY.....................29 W AT 10:58 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE..................30 W AT 11:00 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE.................29 W AT 11:00 A.M.
AVERAGE WIND SPEED AND DIRECTION.............16.0 W 
                   ASOS......................15.8
                   DAVIS.....................15.2 WNW [292 DEG.]
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.00  DEPARTURE......-0.16
                         ASOS..............0.00
TOTAL PRECIPITATION FOR THE MONTH..........1.54  DEPARTURE......-1.70
                         ASOS..............1.63
TOTAL PRECIPITATION FOR THE YEAR..........51.38  DEPARTURE......-0.39
                         ASOS...............N/A **
** ASOS annual total not available due to erroneous readings

SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M..........0.0  DEPARTURE.......-0.6
TOTAL SNOWFALL FOR THE MONTH................5.7  DEPARTURE.......-2.1
TOTAL SNOWFALL FOR THE SEASON...............5.7  DEPARTURE.......-4.7 


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 50/35/43/+6/0.04/262/47          28 NW  AERO 29 NW  RMY 30
12/02 42/29/36/0/0.00/033/06           20 NNW AERO 18 NNW RMY N/A
12/03 42/32/37/+1/0.00/172/31          14 N   AERO 10 N   RMY N/A 
12/04 43/32/38/+3/0.00/522/94          16 E   AERO 14 E   RMY N/A 
12/05 58/34/46/+11/0.18/000/00         62 S   AERO 66 S   RMY 65
12/06 56/32/44/+9/0.54/160/29          52 S   AERO 55 S   RMY N/A
12/07 44/30/37/+3/0.00/540/98          25 WSW AERO 24 WSW RMY 25
12/08 38/28/33/-1/0.00/116/21          21 W   AERO 18 W   RMY 20
12/09 34/28/31/-3./..../000/00         23 NNW AERO 23 NNW RMY 23 
12/10 35/27/31/-2/..../384/70          30 W   AERO 30 W   RMY 27 
12/11 38/29/34/+1/0.00/301/55          23 W   AERO 21 W   RMY 22
12/12 43/31/37/+4/0.06/000/00          35 W   AERO 31 W   RMY N/A
12/13 31/18/25/-7/0.00/312/57          44 W   AERO 44 W   RMY 44
12/14 27/14/21/-11/T/.../..            35 WSW AERO 33 W   RMY 34 
12/15 24/12/18/-14/T/.../..            25 W   AERO 23 W   RMY N/A
12/16 32/17/25/-6/0.00/.../..          33 W   AERO 35 W   RMY 36
12/17 27/14/21/-10/0.00/.../..         21 NW  AERO 21 NW  RMY 20
12/18 35/20/28/-3/T/.../..             20 SSE AERO 16 SSE RMY 20
12/19 49/34/42/+12/T/.../..            36 WNW AERO 35 SW  RMY 38  
12/20 42/26/34/+4/T/.../..             41 W   AERO  40 W  RMY 45 

12/21 Low temp since midnight is 23F; normal low is now 22F

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

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

RECORDS FOR DECEMBER 22
HIGH 63 IN 2013
LOW -5 IN 1921
PRECIP 1.52 INS. IN 1975
SNOWFALL 8.8 INS. IN 1975
PEAK GUST 62 MPH WNW IN 1998

TODAY'S REPORT PREPARED BY: Kaitlin Geagan