BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
  
DAILY DISCUSSION AND CLIMATE SUMMARY
TUESDAY, DECEMBER 11, 2007
ALL TIMES ARE IN EASTERN STANDARD TIME
 
THIN GLAZE REMAINS ON TREES IN SUB-FREEZING WEATHER
THIN RIME ICE OBSERVED THIS MORNING WAS DEPOSITED LATE YESTERDAY
EARLY FREEZES OF NEARBY PONDS 12/4 and 12/6.
 
It was another morning that had treacherous walking conditions
around the instrument area here on the summit. The wearing of 
ice grips made it possible to stay on your feet! An icy crust 
covered the snow and glaze covered rocky surfaces.  
 
Yesterday' maximum temperature was only 30 degrees occurring
during the early morning hours. The freezing weather caused the
thin coating of glaze to remain frozen all day yesterday into 
this morning when our low temperature dropped to a frosty 22 
degrees. Temperatures dropped into the upper 20's during the day
and fog deposited a thin coating of rime ice while the summit was 
in the low clouds. The final precipitation total for the icing 
event was 0.18 inch.
 
December temperatures averaging 25.8 degrees during the first 
ten days of the month places this month close to the averages of 
the cold early Decembers in 2002 and 2003. During 1989 the early
days of the month averaged 19 degrees!  
 
We are reporting the first seasonal freeze-over dates of nearby 
ponds as follows: 
Ponkapoag Pond (1.5 miles SE) on December 4th and decided that 
Houghton's Pond (1.0 mile ESE) became completely frozen over on 
December 6th. This is about 5 days earlier than average for 
Ponkapoag Pond and more than one week earlier than average for 
Houghton's Pond which has an average first freeze date of December
15th.   
 
Today's observations:
 
7 A.M.   
Weather: High thin overcast cirrus/cirrostratus, thin fog 
below summit and inversion, heavy frost/thin rime ice      
Temperature: 23F, Dew point: 20F, Wind: WNW at 7 kts
Sea-level pressure: 30.39 inches Hg, rising 
Visibility: 20 miles, 45 miles WNW above inversion  
6-hour min temp: 22F 
24-hour precip: 0.02   
24-hour snowfall: 0.00  
Snow and ice on ground: 1 inch  
BHO SA 1155 250 –SCT 300 –OVC 20 290/23/20/3007/039/ 
SC OFFSHR DSNT NE-SE THN F BLO INVSN/SMT VSBY 45 ABV 
INVSN WNW HVY FROST/THN RIME ICE/  8/007 4/001 51011 
10025 20023 
  
10 A.M.
Weather: High thin broken cirrus clouds  
Temperature: 29F, Dew point: 26F, Wind: W at 3 kts
Sea-level pressure: 30.42 inches Hg, rising 
Visibility: 12 miles, thin fog, thin smoke along horizons 
Visibility: WNW 50 miles above inversion top estimated 8 hundred feet 
3-hourly precip: 0.00
BHO SA 1455 160 SCT 250 –SCT 300 –BKN 12 300/29/26/2703/042/ 
PTCHS AC SE-SW-W THN F BLO INVSN ESTMTD TOP 8 HND THN K LYR ALG HRZNS 
VSBY WNW 50 ABV INVSN/ 8/041 53010
 
1 P.M.
Weather: Overcast of altocumulus clouds, higher clouds visible,
breaks in overcast    
Temperature: 32F, Dew point: 29F, Wind: S at 6 kts
Sea-level pressure: 30.31 inches Hg, falling 
Visibility: 25 miles, 30 miles NE-S, light haze   
6-hourly precip: 0.00 inch
6-hourly max. temp: 33F
BHO SA 1755 120 SCT E150 OVC 25 264/32/29/1806/031/ 
FEW SC NMRS HIER AC/CI/DENS CI VSB BINOVC ALQDS   
VSBY NE-S 30 LGT HZ ALQDS / 8/572 58036 10033 20022 
 
WEATHER SUMMARY FOR MONDAY, DECEMBER 10
 
TEMPERATURE (DEGREES F)
MAX.....30    NORMAL.....40 
MIN.....26    NORMAL.....25
MEAN....28    NORMAL.....33
DEPARTURE FROM 30-YEAR NORMAL.......... -5 
TOTAL DEPARTURE FOR THE MONTH..........-84 [-8.6 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............37  DEPARTURE......+ 5
TOTAL HEATING UNITS FOR THE MONTH...........390  DEPARTURE......+80 
TOTAL HEATING UNITS FOR THE SEASON.........1470  DEPARTURE.....-124
TOTAL HEATING UNITS LAST SEASON TO DATE....1326  DIFFERENCE....+144
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY............18  N   AT  9:34 A.M.             
                   AEROVANE............. M  (frozen with glaze)        
                   ASOS.................16  N   AT  9:35 A.M.               
                   DAVIS................14  NW  AT  9:06 A.M.               
FASTEST MILE FOR YESTERDAY..............10  N   AT  9:32 A.M.         
MAXIMUM 2-MINUTE ASOS AVERAGE...........12  N   AT  9:35 A.M.           
MAXIMUM 2-MINUTE DAVIS AVERAGE..........11  NNW AT  9:11 A.M.              
AVERAGE WIND SPEED AND DIRECTION........5.5 N  
                   ASOS.................5.8        
                   DAVIS................4.8 NNW [340 deg]     
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.02  DEPARTURE....-0.13
                         ASOS..............0.02 
TOTAL PRECIPITATION FOR THE MONTH..........0.90  DEPARTURE....-0.60
                         ASOS..............0.89  
TOTAL PRECIPITATION FOR THE YEAR..........39.74  DEPARTURE....-8.42
                         ASOS.............39.11  
 
SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M......... 0.0  DEPARTURE.....-0.3
TOTAL SNOWFALL FOR THE MONTH................2.7  DEPARTURE.....+0.1 
TOTAL SNOWFALL FOR THE SEASON...............3.5  DEPARTURE.....-2.0
 
PRELIMINARY CLIMATE SUMMARY FOR DECEMBER 2007...CALENDAR DAY DATA
DATA REPORTED:
DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST
 
AERO: Aerovane recording wind system when significant
TSTM: Thunderstorm day
....: Data not yet available
 
12/1  33/15/24/-12/0/0/493/88       54 WNW 
12/2  24/15/20/-16/0.03/0.3/000/00  28 WNW 
12/3  38/23/31/-4/0.62/1.7/000/00   47 W 
12/4  27/17/22/-13/T/T/106/19       48 W       
12/5  29/17/23/-12/T/T/239/43       23 WNW
12/6  28/15/22/-12/0/0/554/100      31 WNW
12/7  34/21/28/-6/0.07/0.7/.../..   24 SSW
12/8  41/25/33/0/0/0/.../..         32 W
12/9  33/25/29/-4/0.08/T/000/00     16 NW  
12/10 30/26/28/-5/0.10/0/000/00     18 N 
  
12/11 morning low temp. 22F; the normal low is now 25F
 
NEW DAILY RECORDS FOR DECEMBER 2007: NONE
 
DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR DECEMBER 11
HIGH 63 IN 1911
LOW -1 IN 1988
PRECIP 2.36 INS. IN 1992
SNOWFALL 6.0 INS. IN 1894
PEAK GUST 78 S IN 1969
 
RECORDS FOR DECEMBER 12
HIGH 67 IN 1979
LOW -3 IN 1988
PRECIP 3.94 INS. IN 1992
SNOWFALL 20.3 INS. IN 1960
PEAK GUST 74 MPH W IN 2000
 
TODAY'S REPORT PREPARED By: Robert Skilling