Wednesday, December 13, 2017

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

DAILY DISCUSSION AND CLIMATE SUMMARY
WEDNESDAY, DECEMBER 13, 2017
ALL TIMES ARE IN EASTERN STANDARD TIME

WIND SHIFT OVERNIGHT BRINGS COLD DRY AIR TO
GREAT BLUE HILL…

With the wind coming from the ESE yesterday, we
had slightly above average temperatures with a
mean temperature of 37F. This is 4 degrees above
the normal daily mean of 33F. Overnight winds
from the ESE shifted to the WNW and temperatures
began to rapidly drop with an overnight low of
18F. This is a 25 degree drop in temperature in
12 hrs. Our high so far today is 22F, which is
18 degrees below the normal of 40F.
We have a very strong westerly wind today with a
peak gust of 38 kts (44 MPH). This made the air
feel colder with -1F degree wind chill during
this gust. The air has also been dry with
humidity dropping from throughout the day
allowing for 60 miles of visibility by 1:00 P.M.

Today’s Observations:

7 A.M.
Weather: Scattered altocumulus and scattered cirrostratus
Temperature: 19F; Dew Point: 9F; Wind: W at 12G22 kts
Sea-level pressure: 29.27 ins. Hg, rising then steady
Visibility: 45 miles, distant fog in all directions
6-hr Max temp: 31F
6-hr Min temp: 18F
24-hr precip: 0.06 ins.
24-hr snowfall: 0.0 ins.
Snow cover: 1 in.
BHO SA 1155 70 SCT 250 SCT 45 913/19/09/2612G22/927/ DSNT FG
ALQDS/ 8/035 4/001 MANUAL 70006 ASOS 70006 51007 10031 20018

10 A.M.
Weather: Scattered altocumulus, few cumulus in all directions
Temperature: 20F; Dew Point: 7F; Wind: W at 16G30 kts,
Peak Wind: 33 kts (38 MPH) at 9:42 A.M. EST
Sea-level pressure: 29.29 ins. Hg, rising, then more slowly
Visibility: 45 miles, distant fog in all directions
3-hr precip: 0.00 ins.
3-hr snowfall: 0.0 ins.
BHO SA 1455 70 SCT 45 919/20/07/2616G30/929/ FEW CU ALQDS
DSNT FG ALQDS PK WND 2633/42/ 8/150 53006

1 P.M.
Weather: Scattered cumulus, broken stratocumulus
Temperature: 22F; Dew Point: 7F; Wind: W at 24G32 kts,
Peak Wind: 38 kts (44 MPH) at 12:12 P.M. EST
Sea-level pressure: 29.28 ins. Hg, falling, then more quickly
Visibility: 60 miles
6-hr Max temp: 22F
6-hr Min temp: 19F
6-hr precip: 0.00 ins.
6-hr snowfall: 0.0 ins.
Snow cover: 1 in.
BHO SA 1755 32 SCT E50 BKN 60 915/22/07/2724G32/928/ PK WND
2738/12/ 8/800 4/001 55004 10022 20019

SUMMARY FOR TUESDAY, DECEMBER 12, 2017

TEMPERATURE (DEGREES F)
MAX…..43   NORMAL…..40
MIN…..31   NORMAL…..25
MEAN….37   NORMAL…..33

DEPARTURE FROM 30-YEAR NORMAL………………………+4
TOTAL DEPARTURE FOR THE MONTH……………………..+32 [+2.5 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY………….28  DEPARTURE……….-4
TOTAL HEATING UNITS FOR THE MONTH…………333  DEPARTURE………-33
TOTAL HEATING UNITS FOR THE SEASON……….1302  DEPARTURE……..-325
TOTAL HEATING UNITS LAST SEASON TO DATE…..1402  DIFFERENCE…….-100

PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY……………….35 W AT 6:33 P.M.
AERO……………………31 W AT 6:34 P.M.
ASOS……………………33 W AT 6:34 P.M.
DAVIS…………………..33 W AT 6:33 A.M. RMY N/A
FASTEST MILE FOR YESTERDAY…………………21 W AT 6:32 P.M.
MAXIMUM 2-MINUTE ASOS AVERAGE………………23 W AT 6:35 P.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE……………..22 W AT 6:35 P.M.
AVERAGE WIND SPEED AND DIRECTION………….13.1 ESE
ASOS………………….13.0
DAVIS…………………12.5 SE [137 DEG.]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M….0.06  DEPARTURE……-0.11
ASOS…………..0.06
TOTAL PRECIPITATION FOR THE MONTH……….1.54  DEPARTURE……-0.44
ASOS…………..1.63
TOTAL PRECIPITATION FOR THE YEAR……….51.38  DEPARTURE……+0.87
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…….-0.4
TOTAL SNOWFALL FOR THE MONTH…………….5.6  DEPARTURE…….+1.6
TOTAL SNOWFALL FOR THE SEASON……………5.6  DEPARTURE…….-1.0

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/…/000/00          62 S   AERO 66 S   RMY 65
12/06 56/32/44/+9/…/160/29           52 S   AERO 55 S   RMY N/A
12/07 44/30/37/+3/0.00/522/98          25 WSW AERO 24 WSW RMY 25
12/08 38/28/33/-1/0.00/…/..          21 W   AERO 18 W   RMY 20
12/09 34/28/31/-3./…./…/..         23 NNW AERO 23 NNW RMY 23
12/10 35/27/31/-2/…./…/..          30 W   AERO 30 W   RMY 27
12/11 38/29/34/+1/0.00/…/..          23 W   AERO 21 W   RMY 22
12/12 43/31/37/+4/0.06/…/..          35 W   AERO 31 W   RMY N/A

12/13 Low temp since midnight is 18F; normal low is now 25F

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

RECORDS FOR DECEMBER 13
HIGH 60 IN 1984
LOW 0 IN 1893
PRECIP 1.45 INS. IN 1983
SNOWFALL 9.2 INS. IN 2007
PEAK GUST 81e WNW IN 1976

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

TODAY’S REPORT PREPARED BY: Kaitlin Geagan