Tuesday, December 20, 2016

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

DAILY DISCUSSION AND CLIMATE SUMMARY
TUESDAY, DECEMBER 20, 2016

WINDS SHIFT SOUTH, CLOUD COVER INCREASES AS FRONT APPROACHES,
FIRST POND FREEZE OF THE SEASON CONFIRMED

This morning was another cold start with a low temp. of 13F.
Temps rebounded to 30F by 1:00PM, but were still slightly
cooler than average.  Visibility was able to improve to 70 miles
in all directions as rising temps. helped to dissipate a thin
layer of smoke along the horizon.  An approaching front brought
us cloudy, afternoon skies and a southerly wind shift during
late morning.

The first freeze date of the season for both Houghton’s and
Ponkapoag Ponds was confirmed to be yesterday, December 19,
almost one week and two weeks later, respectively, than their
average freeze dates.  The average freeze date for Ponkapoag
Pond is December 7, and the average freeze date for Houghton’s
Pond is December 13.

7 A.M.
Weather: Scattered stratocumulus, few cirrus in all directions
Temperature: 13F; Dew Point: 0F; Wind: NNW at 7 kts
Sea-level pressure: 30.59 ins. Hg, falling unsteadily
Visibility: 40 miles, except 70 miles SSW-N, thin smoke layer along
horizon in all directions
6-hr Max temp: 17F
6-hr Min temp: 13F
24-hr precip: 0.00 in.
BHO SA 1155 32 SCT 40 360/13/00/3307/059/ FEW CI ALQDS VSBY SSW-N 70
THN K LYR ALQDS ALNG HRZN/ 8/501 57006 10017 20013

10 A.M.
Weather: Scattered altocumulus, few cirrus in all directions
Temperature: 21F; Dew Point: 7F; Wind: estimated WNW at 3 kts,
Wind Speed: Light
Sea-level pressure: 30.57 ins. Hg, falling, then more quickly
Visibility: 40 miles, except 70 miles SSW-N, thin smoke layer along
horizon in all directions, looming on mountains WNW-NW
BHO SA 1455 84 SCT 40 352/21/07/E3003/057/ FEW CI ALQDS VSBY SSW-N 70
THN K LYR ALQDS ALNG HRZN WND LGT LOOMING OF MTNS WNW-NW/ 8/031 58008

1 P.M.
Weather: Broken stratocumulus, scattered cirrostratus
Temperature: 30F; Dew Point: 15; Wind: SSW at 4 kts,
Wind Speed: Light
Sea-level pressure: 30.44 ins. Hg, falling, then more slowly
Visibility: 70 miles
6-hr Max temp: 30F
6-hr Min temp: 13F
BHO SA 1755 E24 BKN 250 SCT 70 309/30/15/2004/044/ WND LGT/
8/508 56043 10030 20013

SUMMARY FOR MONDAY, DECEMBER 19, 2016

TEMPERATURE (DEGREES F)
MAX…..30   NORMAL…..38
MIN…..17   NORMAL…..23
MEAN….24   NORMAL…..30

DEPARTURE FROM 30-YEAR NORMAL……………………-6
TOTAL DEPARTURE FOR THE MONTH…………………..-32 [-1.9 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY…………..41   DEPARTURE……….+6
TOTAL HEATING UNITS FOR THE MONTH………….633   DEPARTURE………+30
TOTAL HEATING UNITS FOR THE SEASON………..1663   DEPARTURE……..-201
TOTAL HEATING UNITS LAST SEASON TO DATE……1391   DIFFERENCE…….+272

PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY……………….26 WNW AT 9:16 A.M.*
ASOS……………………28 N   AT 9:17 A.M.
DAVIS…………………..25 WNW AT 6:20 A.M. RMY 26
FASTEST MILE FOR YESTERDAY…………………20 WNW AT 6:20 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE………………21 NNW AT 6:22 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE……………..20 W   AT 6:22 A.M.
AVERAGE WIND SPEED AND DIRECTION………….10.0 WNW
ASOS…………………..9.6
DAVIS………………….9.1 WNW [290 Deg.] *last of multiple occurrences

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M….0.00  DEPARTURE……-0.15
ASOS…………..0.00
TOTAL PRECIPITATION FOR THE MONTH……….1.49  DEPARTURE……-1.59
ASOS…………..1.64
TOTAL PRECIPITATION FOR THE YEAR……….38.46  DEPARTURE…..-13.15
ASOS………….39.07

SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M……….0.0  DEPARTURE…….-0.5
TOTAL SNOWFALL FOR THE MONTH…………….6.0  DEPARTURE…….-1.2
TOTAL SNOWFALL FOR THE SEASON……………6.0  DEPARTURE…….-3.8

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

12/1  55/39/47/+10/0.20/0.0/385/69          36 W   AERO 37 W   RMY 36
12/2  48/34/41/+5/0.00/0.0/535/96           32 W   AERO 32 W   RMY N/A
13/3  44/31/38/+2/0.00/0.0/445/80           37 WNW AERO 39 WNW RMY 40
12/4  39/27/33/-2/0.00/0.0/355/64           25 NW  AERO 25 NW  RMY N/A
12/5  36/27/32/-3/0.13/0.4/000/00           26 W   AERO 25 W   RMY 29
12/6  42/30/36/+1/0.00/0.0/392/71           22 W   AERO 21 W   RMY N/A
12/7  39/34/37/+3/0.10/0.0/000/00           21 E   AERO 21 E   RMY N/A
12/8  40/29/35/+1/0.00/0.0/033/06           30 W   AERO 31 W   RMY 33
12/9  35/21/28/-6/0.00/0.0/549/100          35 W   AERO 36 WNW RMY 34
12/10 27/17/22/-11/0.00/0.0/544/99          26 WNW AERO 27 WNW RMY 29
12/11 33/16/25/-8/0.06/0.4/411/75           17 SSW AERO 15 SW  RMY N/A
12/12 41/27/34/+1/0.35/0.9/038/07           29 ESE AERO 29 SE  RMY 30
12/13 41/30/36/+4/0.00/0.0/…/..           25 WSW AERO 25 W   RMY 27
12/14 40/26/33/+1/0.00/0.0/…/..           30 WNW AERO 31 WNW RMY N/A
12/15 29/13/21/-11/T/T/…/..               50 W   AERO 62 W   RMY 56
12/16 18/01/10/-21/0.00/0.0/…/..          39 WNW AERO 51 WNW RMY N/A
12/17 36/18/27/-4/…./4.3/…/..           25 SSW AERO 28 SSW RMY N/A
12/18 55/30/43/+12/…./0.0/…/..          47 WSW AERO 53 S   RMY 53
12/19 30/17/24/-6/0.00/0.0/…/..           26 WNW*AERO 28 NW  RMY 26

12/20 Low temp since midnight is 13F; 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 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

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

TODAY’S REPORT PREPARED BY: Cecilia Borries-Strigle