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

DAILY DISCUSSION AND CLIMATE SUMMARY
WEDNESDAY, DECEMBER 19, 2018 
ALL TIMES ARE IN EASTERN STANDARD TIME

A FAIR WEATHER DAY WITH A NOTABLE TEMPERATURE
INCREASE AND PLUMMETING HUMIDITY....

We observed a temperature increase of 20 degrees since 7 A.M.,
from 17F to a high of 37F so far today. That is 1 degree 
below the daily normal of 38F. The low since midnight is 
17F, 6 degrees below the normal minimum of 23F. Visibility
has made a notable increase from 40 miles this morning to 
80 miles. This is due to a humidity decrease to almost 30% 
and a distant smoke layer dissipating by the 1 P.M. observation.
Winds have stayed light and westerly in contrast to much stronger 
winds observed yesterday. 


Today's Observations:

7 A.M.
Weather: Scattered cirrus
Temperature: 17F; Dew Point: 11F; Wind: W at 10 kts   
Sea-level pressure: 30.10 ins. Hg, rising steadily       
Visibility: 40 miles, thin smoke layer 
6-hr Max temp: 19F
6-hr Min temp: 17F
24-hr Precip: 0.00 ins.
24-hr snowfall: 0.0 ins.
Snow depth: 0 ins.   
BHO SA 1155 250 SCT 40 192/17/11/2810/010/ THN K 
LYR ALQDS/ 8/002 51013 10019 20017  

10 A.M.
Weather: Scattered cirrus  
Temperature: 26F; Dew Point: 12F; Wind: W at 6G13 kts,
Wind: Light    
Sea-level pressure: 30.13 ins. Hg, rising steady
Visibility: 70 miles, thin smoke layer
3-hr Precip: 0.00 ins. 
BHO SA 1455 250 SCT 70 202/26/12/2806G13/013/ THN K 
LYR ALQDS WND LGT/ 8/002 51010 

1 P.M.
Weather: Scattered cirrus   
Temperature: 36F; Dew Point: 9F; Wind: WNW at 5 kts,
Wind: Light     
Sea-level pressure: 30.07 ins. Hg, falling, then more rapidly      
Visibility: 80 miles
6-hr Max temp: 37F
6-hr Min temp: 17F
6-hr Precip: 0.00 ins.
6-hr snowfall: 0.0 ins.
Snow depth: 0 ins.   
BHO SA 1755 250 SCT 80 184/36/9/3005/007/ WND LGT/ 
8/002 56018 10037 20017
 
SUMMARY FOR TUESDAY, DECEMBER 18, 2018 

TEMPERATURE (DEGREES F)
MAX.....34   NORMAL.....38
MIN.....20   NORMAL.....23
MEAN....27   NORMAL.....31

DEPARTURE FROM 30-YEAR NORMAL........................-4
TOTAL DEPARTURE FOR THE MONTH.......................-27 [-1.7 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY..............38   DEPARTURE.........+3
TOTAL HEATING UNITS FOR THE MONTH.............593   DEPARTURE........+25
TOTAL HEATING UNITS FOR THE SEASON...........1913   DEPARTURE........+84
TOTAL HEATING UNITS LAST SEASON TO DATE......1554   DIFFERENCE......+359

PEAK GUST AND AVERAGE WIND SPEED (MPH) 
PEAK WIND GUST FOR YESTERDAY....................48 NW  AT  3:38 A.M.
                   AERO.........................55 NW  AT  3:33 A.M. 
                   ASOS.........................55 NW  AT  5:06 A.M. 
                   DAVIS........................52 NW  AT  3:41 A.M. RMY 48
FASTEST MILE FOR YESTERDAY......................39 NW  AT  3:28 A.M. 
MAXIMUM 2-MINUTE ASOS AVERAGE...................36 NW  AT  3:32 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE..................39 NW  AT  3:32 A.M.
AVERAGE WIND SPEED AND DIRECTION..............21.6 NW
                   ASOS.......................20.4
                   DAVIS......................21.2 NW [315 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..........1.95  DEPARTURE.......-0.98
                         ASOS..............2.68 *
TOTAL PRECIPITATION FOR THE YEAR..........65.32  DEPARTURE......+14.05
                         ASOS.............68.31 *
* ASOS MONTHLY AND ANNUAL PRECIPITATION IS SUSPECT

SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M..........0.0  DEPARTURE........-0.4
TOTAL SNOWFALL FOR THE MONTH................0.1  DEPARTURE........-6.6
TOTAL SNOWFALL FOR THE SEASON...............7.7  DEPARTURE........-1.6

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 41/28/35/-2/0.00/0.0/391/70          20 NNW AERO 18 NNW RMY N/A
12/02 52/35/44/+8/1.04/0.0/000/00          28 ESE AERO 25 ESE RMY 27
12/03 54/38/46/+10/0.00/0.0/178/32         35 W   AERO 35 W   RMY 38 
12/04 38/23/31/-4/0.00/0.0/516/93          30 WNW AERO 31 WNW RMY 33
12/05 33/18/26/-9/0.00/0.0/432/78          16 NNW AERO 15 NNW RMY N/A
12/06 37/24/31/-4/0.00/0.0/354/64          29 W   AERO 28 W   RMY 30
12/07 37/21/29/-5/0.00/0.0/.../..          29 NW  AERO 29 NW  RMY 32
12/08 27/15/21/-13/0.00/0.0/.../..         28 NW  AERO 27 NW  RMY 29
12/09 34/17/26/-8/0.00/0.0/.../..          23 SSW AERO 21 SSW RMY 22
12/10 36/22/29/-4/0.00/0.0/.../..          24 NNW AERO 23 NNW RMY 22
12/11 36/17/27/-6/0.00/0.0/.../..          16 WSW AERO 14 WSW RMY N/A
12/12 35/18/27/-6/0.00/0.0/.../..          30 NW  AERO 29 NW  RMY M
12/13 31/16/24/-8/0.00/0.0/.../..          16 NNE AERO 12 SE  RMY N/A
12/14 46/28/37/+5/0.00/0.0/.../..          28 SSW AERO 28 SSW RMY 29
12/15 49/33/43/+11/0.04/0.0/.../..         28 NE  AERO 27 NE  RMY 30
12/16 40/37/39/+8/..../0.0/.../..          38 NE  AERO 38 NE  RMY 40
12/17 37/32/35/+4/..../0.0/.../..          39 NNE AERO 37 NNE RMY N/A
12/18 34/20/27/-4/0.02/0.1/.../..

12/19 Low temp since midnight is 17F; normal low is 23F


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

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

RECORDS FOR DECEMBER 20
HIGH 61 IN 1957
LOW -16 IN 1942
PRECIP 1.69 INS. IN 1936
SNOWFALL 13.7 INS. IN 2009
PEAK GUST 75 MPH S IN 2002

TODAY'S REPORT PREPARED BY: Benjamin Turner