BLUE HILL OBSERVATORY MILTON, MA
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
THURSDAY, SEPTEMBER 23, 2010
ALL TIMES ARE IN EASTERN STANDARD TIME
 
SUMMER-LIKE DAY AS AUTUMN BEGINS
COOLER AND DRIER CONDITIONS TODAY 
 
The arrival of the autumn season was marked by the
autumnal equinox occurring at 11:09 PM EDT late
yesterday. Starting out with a mild low temperature
of 58F early yesterday our afternoon high reading
touched 84F, the warmest maximum since 80F way back
on September 8.
The air mass became moderately humid with dew points
rising into the mid-60's.  A brief light rain shower was
observed between 9:30 and 10 PM last evening leaving
just a trace of precipitation.  While temperatures fell
slowly from 73F at 8 PM to a low of 60F this morning,
the most noticeable change was the arrival of drier air
as dew points fell into the 50s.
 
Today's observations: 
 
7 A.M.
Weather: Overcast dense cirrostratus, break in overcast with
patches of clear sky bands N-E-S, sun visible
Temperature: 61F, Dew point: 52F; Wind: NNW at 9 kts
Sea-level pressure: 30.19 inches Hg, rising 
Visibility: 50 miles, W-NW 60, NE-S 35, light distant haze
6-hour minimum temp: 60F
24-hour precip: trace
BHO SA 1155 180 SCT E200 OVC 50 222/61/52/3409/019/ BINOVC/PTCHS 
CLR SKY BNDS DSNT N-E-S SUN VSB VSBY W-NW 60 NE-S 35/LGT DSNT HZ/
8/007 51026 10069 20060
 
10 A.M.
Weather: Scattered dense cirrus, thin overcast cirrus and
cirrostratus, large break in overcast SSW-W 
Temperature: 68F, Dew point: 61F; Wind: NNE at 6 kts,
Wind: Light and gradually veering  
Sea-level pressure: 30.25 inches Hg, rising
Visibility: 60 miles, 70 W-NW, 30 NE-E with light haze 
BHO SA 1455 220 SCT 250 –OVC 60 242/68/61/0306/025/
DNS CI/CS MSTLY DSNT NW-NE LGE BINOVC SSW-W VSBY W-NW 70
LGT HZ NE-E VSBY 30 WND LGT GRDLY VEERING/ 8/002 51020
 
1 P.M.  
Weather: Scattered dense cirrus, thin broken cirrus radiatus
Temperature: 82F, Dew point: 64F; Wind: ESE at 4 kts,
Wind: Light
Sea-level pressure: 30.21 inches Hg, falling
Visibility: 75 miles 
6-hourly max. temp: 73F
BHO SA 1755 220 SCT 250 –BKN 300 –BKN 75 230/82/64/1104/021/ 
PTCHS DNS CI WND LGT/ 8/002 58012 10073 20061
  
WEATHER SUMMARY FOR WEDNESDAY, SEPTEMBER 22
 
TEMPERATURE (DEGREES F)
MAX.....84     NORMAL.....69
MIN.....58     NORMAL.....51
MEAN....71     NORMAL.....60       
DEPARTURE FROM 30-YEAR NORMAL.............+11
TOTAL DEPARTURE FOR THE MONTH.............+50 [+2.1 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY.............0    DEPARTURE........-6
TOTAL HEATING UNITS FOR THE MONTH............57    DEPARTURE.......-23
TOTAL HEATING UNITS FOR THE SEASON...........70    DEPARTURE.......-41
TOTAL HEATING UNITS LAST SEASON TO DATE.....110    DIFFERENCE......-40
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY.............32 SSW AT  8:52 A.M. 
                   AEROVANE..............36 SSW AT 10:02 A.M.   
                   ASOS..................33 SSW AT  8:52 A.M.      
                   DAVIS.................36 SSW AT  8:52 A.M.   
THE FASTEST MILE FOR YESTERDAY...........26 SSW AT 10:05 A.M. *   
MAXIMUM 2-MINUTE ASOS AVERAGE............25 S   AT  1:29 A.M.     
MAXIMUM 2-MINUTE DAVIS AVERAGE...........28 SSW AT 10:05 A.M.  
AVERAGE WIND SPEED AND DIRECTION.......16.2 SSW
                   ASOS................15.4
                   DAVIS...............16.6 SSW [210 DEG]
* Last of several occurrences...
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M...trace  DEPARTURE........-0.14
                         ASOS..............0.00
TOTAL PRECIPITATION FOR THE MONTH..........1.08  DEPARTURE........-1.93
                         ASOS..............1.05
TOTAL PRECIPITATION FOR THE YEAR..........47.11  DEPARTURE.......+10.63
                         ASOS.............46.89 **
** ASOS missing rainfall due to system failure on 6/24-25
 
PRELIMINARY CLIMATE SUMMARY FOR SEPTEMBER 2010 CALENDAR DAY DATA
DATA REPORTED:
DATE: MAX/MIN/MEAN/DEP/PRECIP/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
 
9/1  93/73/83/+16/0.00/765/97  18 SW
9/2  93/72/83/+17/0.00/740/94  25 SSW
9/3  83/69/76/+10/0.47/039/05  25 NNE
9/4  79/62/71/+5/0.00/672/86   37 WSW  AERO 39 MPH WSW
9/5  73/55/64/-1/0.00/778/100  28 SW   AERO 32 MPH SW
9/6  76/54/65/0/T/768/99       22 SSW
9/7  84/62/73/+8/0.00/440/57   30 SSW  AERO 32 MPH S 
9/8  80/59/70/+5/0.08/300/39   35 W    AERO 40 MPH W TSTM *
9/9  72/55/64/0/T/352/46       28 W
9/10 67/55/61/-3/0.00/260/34   26 WNW
9/11 68/53/61/-3/0.00/723/95   18 NE
9/12 63/54/59/-4/T/045/06      22 ENE  AERO 24 MPH NE
9/13 67/54/61/-2/0.02/091/12   22 S
9/14 74/53/64/+1/T/489/65      31 WSW  AERO 32 MPH WSW
9/15 67/49/58/-4/0.00/660/88   28 W    AERO 31 MPH W
9/16 70/46/58/-4/0.26/530/71   43 S
9/17 68/53/61/-1/0.25/000/00   45 S
9/18 65/53/59/-2/0.00/193/26   15 SE
9/19 76/54/65/+4/T/451/61      17 SW   AERO 22 MPH SW
9/20 69/50/60/-1/0.00/707/96   29 NW   AERO 33 MPH NW
9/21 70/46/58/-2/0.00/711/97   31 S    AERO 35 MPH S
9/22 84/58/71/+11/T/.../..     32 SSW  AERO 36 MPH SSW  
 
9/23 our overnight low temp: 60F; the normal low is now 51F
 
* thunderstorm day added....
 
NEW DAILY RECORDS FOR SEPTEMBER 2010
9/1 - High maximum temperature of 93F equals the previous
record of 93F set in 1969
9/1 - High minimum temperature of 73F surpasses the previous
record of 71F in 1898, 1959
9/2 - High minimum temperature of 72F surpasses the previous
record of 71F in 1959
 
DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR SEPTEMBER 23
HIGH 93F IN 1895,1914
LOW 33F IN 1904
PRECIP 2.67 INCHES IN 1994
PEAK GUST 62 MPH SSW IN 1989
 
RECORDS FOR SEPTEMBER 24
HIGH 87F IN 1959
LOW 33F IN 1885,1950,1963
PRECIP 1.19 INCHES IN 1955
PEAK GUST 54e MPH SW IN 1940
 
TODAY'S REPORT PREPARED BY: Robert Skilling