BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
THURSDAY, DECEMBER 17, 2009
ALL TIMES ARE IN EASTERN STANDARD TIME
 
STRONG WINDS GUST OVER 50 MPH FROM THE WNW
AS 2ND BURST OF ARCTIC AIR ARRIVED EARLY TODAY
COLDEST AIR OF SEASON BRINGS LOW OF 12F WITH
WINDCHILLS DOWN NEAR 7 BELOW ZERO  
 
A reinforcing shot of Arctic air arrived during
the early morning hours of today with west winds
veering to west-northwest and becoming increasingly
gusty after 3 a.m.  Peak gusts reached 52 MPH WNW
at 5:43 a.m. A couple of our other wind systems
(Maximum, Inc.) had gusts to 58 and 59 MPH WNW.
Temperatures began dropping sharply after 3 a.m.
when it was still 20F to 13F by 7 a.m. and to a
low of 12F between 8 and 9 a.m. This was our coldest
since last March 4th when the low was 6F. Windchill
temperatures dropped to near 7 below zero during the
strong winds this morning.
 
Today's observations:
 
7 A.M.
Weather: Clear, stratocumulus along and offshore NE-SE
and distant southeast thru southwest
Temperature: 13F, Dew point: 0F, Wind: WNW at 25G31 kts,
Wind: Peak wind gust 42 kts from WNW at 6:14 a.m.,
Wind: Direction variable WSW to NW
Windchill: -7F
Sea-level pressure: 30.11 inches Hg, rising
Visibility: 55 miles
6-hour minimum temp: 13F
24-hour precipitation: 0.00
24-hour snowfall: 0.00
Average snow depth: none
BHO SA 1155 CLR 55 196/13/0/2925G39/011/ SC ALG/OFFSHR NE-SE 
AND DSNT SSE-SW PK WND 2842/14/ WND 25V31 WNDCHILL -7/ 
8/500 52016 10022 20013
 
10 A.M.
Weather: Clear, few stratocumulus distant offshore NE-SE and
to the distant south
Temperature: 14F, Dew point: -1F, Wind: W at 17G27 kts,
Wind: Peak wind gust 35 kts WNW at 9:07 a.m.,
Wind; Direction variable WSW to NW
Sea-level pressure: 30.15 inches Hg, rising 
Visibility: 60 miles 
BHO SA 1455 CLR 60 210/14/-1/2817G27/015/ FEW SC DSNT OFFSHR 
NE-SE AND DSNT S PK WND 2935/07/ WND 24V31/ 8/500 51014
 
1 P.M.
Weather: Clear, stratocumulus offshore distant NE-ESE  
Temperature: 18F, Dew point: 0F, Wind: W at 17G24 kts,
Wind: Peak wind gust 27 kts W @ 12:07 p.m.,
Wind: Direction variable WSW to NW 
Sea-level pressure: 30.11 inches Hg, falling  
Visibility: 60 miles, 70 miles northwest
6-hour max. temp: 18F  
BHO SA 1755 CLR 60 196/18/0/2817G24/011/ SC DSNT OFFSHR NE-ESE 
VSBY NW 70 PK WND 2727/07/ WND 24V31/ 8/500 58014 10018 20012
 
WEATHER SUMMARY FOR WEDNESDAY, DECEMBER 16
 
TEMPERATURE (DEGREES F)
MAX.....35     NORMAL.....38
MIN.....22     NORMAL.....24
MEAN....29     NORMAL.....31
 
DEPARTURE FROM 30-YEAR AVERAGE.............-2
TOTAL DEPARTURE FOR THE MONTH.............+33  [+1.9 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............36    DEPARTURE........+2
TOTAL HEATING UNITS FOR THE MONTH...........474    DEPARTURE.......-29
TOTAL HEATING UNITS FOR THE SEASON.........1634    DEPARTURE......-158
TOTAL HEATING UNITS LAST SEASON TO DATE....1705    DIFFERENCE......-71
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY.............43 W   AT  5:42 A.M.   
                   AEROVANE..............44 W   AT  5:42 A.M.   
                   ASOS..................41 W   AT  5:41 A.M.   
                   DAVIS.................44 W   AT  5:41 A.M.   
THE FASTEST MILE FOR YESTERDAY...........33 W   AT  5:41 A.M. 
MAXIMUM 2-MINUTE ASOS AVERAGE............31 W   AT  5:42 A.M.   
MAXIMUM 2-MINUTE DAVIS AVERAGE...........33 W   AT  5:42 A.M.  
AVERAGE WIND SPEED AND DIRECTION.......19.4 W 
                   ASOS................17.1  
                   DAVIS...............18.8 W [280 DEG]
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.00   DEPARTURE....-0.14
                         ASOS..............0.00
TOTAL PRECIPITATION FOR THE MONTH..........3.94   DEPARTURE....+1.59
                         ASOS..............4.01
TOTAL PRECIPITATION FOR THE YEAR..........53.51   DEPARTURE....+4.50
                         ASOS.............54.77
                 
SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M......... 0.0  DEPARTURE.....-0.4
TOTAL SNOWFALL FOR THE MONTH...............11.0  DEPARTURE.....+6.3
TOTAL SNOWFALL FOR THE SEASON..............14.0  DEPARTURE.....+6.4
                                               
PRELIMINARY CLIMATE SUMMARY FOR DECEMBER 2009 CALENDAR DAY DATA
DATA REPORTED:
DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST
AERO: Aerovane wind recording system gust when significant
TSTM: Thunderstorm day (thunder heard some time during day)
....: Data not yet available, records not finalized
 
12/1  41/28/35/-1/0/0/497/89       29 NW 
12/2  51/33/42/+6/0.08/0/345/62    30 SSE
12/3  67/47/57/+22/1.01/0/428/77   69 SSE  AERO 73 MPH SSE
12/4  52/40/46/+11/0/0/488/88      26 W
12/5  42/30/36/+1/0.79/4.7/000/00  36 N
12/6  33/25/29/-5/0.09/0.6/513/93  36 NW
12/7  36/25/31/-3/0/0/050/09       22 WSW
12/8  39/25/32/-3/0/0/512/93       27 WNW
12/9  45/29/37/+4/1.23/5.7/000/00  52 ENE  AERO 46 MPH ENE
12/10 40/26/33/0/0/0/351/64        46 WSW  AERO 39 MPH W
12/11 26/20/23/-9/0/0/395/72       46 WSW  AERO 41 MPH WSW
12/12 30/18/24/-8/0/0/.../..       36 W    AERO 33 MPH W 
12/13 46/23/35/+3/0.74/0/.../..    35 SSE  AERO 31 MPH SSE
12/14 41/33/37/+6/0/0/.../..       29 NW
12/15 46/34/40/+9/0/0/006/01       35 W    AERO 32 MPH W
12/16 35/22/29/-2/T/T/464/85       43 W    AERO 44 MPH W
 
12/17 our morning low temp. thru 7 a.m.: 13F; the normal low is 23F 
 
NEW DAILY RECORD FOR DECEMBER 2009
12/3 NEW RECORD HIGH MAXIMUM TEMPERATURE of 67F;
     surpasses previous record of 61F in 1932, 1950.
 
DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR DECEMBER 17
HIGH 63 IN 2000
LOW -10 IN 1942
PRECIP 3.03 INS. IN 1888
SNOWFALL 7.5 INS. IN 1988
PEAK GUST 78 MPH SSE IN 2000
 
RECORDS FOR DECEMBER 18
HIGH 59 IN 1928
LOW -11 IN 1919
PRECIP 1.44 INS. IN 1915
SNOWFALL 7.0 INS. IN 1904
PEAK GUST 76e W IN 1978
 
TODAY'S REPORT PREPARED BY: Robert Skilling