BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
SUNDAY, SEPTEMBER 20, 2009 
ALL TIMES ARE IN EASTERN STANDARD TIME
 
HIGH PRESSURE BRINGING SUNNY BUT COOL WEEKEND
TEMPERATURES DROP TO 45F FOR A SECOND MORNING
AUTUMNAL EQUINOX OCCURS IN JUST TWO DAYS
 
A large high pressure system has been accompanied
by the coolest and driest air of this very late
astronomical summer season.  This morning the low
temperature reading was again 45F for a second
morning in a row after a cool day yesterday when
the high reading could only reach 65F despite a
very sunny day. Temperatures averaging 6 degrees
below normal further reduced the monthly mean
to almost 2 degrees cooler than normal.
Astronomical summer ends with the autumnal equinox
in just a couple of days on Tuesday, 22 September
at 5:18 P.M.
 
Today's observations:
 
7 A.M.  
Weather: Clear, few thin cirrus distant NW-E, inverson,
few distant patches dense shallow ground, few patches thin
steam fog over ponds in our vicinity to the southeast
dissipating past hour 
Temperature: 51F, Dew point: 39F, Wind: WNW at 6 kts
Sea-level pressure: 30.35 inches Hg, rising
Visibility: 80 miles
6-hour minimum temp: 45F
24-hour precipitation: 0.00
BHO SA 1155 CLR 80 276/51/39/2906/035/ THN CI DSNT NW-E INVSN 
FEW PTCHS DSNT DENS GF DSSPTNG PST HR FEW PTCHS THN STEAM
FG OVR PONDS VCNTY STN SE/ 8/001 53008 10051 10045   
 
10 A.M.
Weather: Clear, line of cumulus distant SSE, thin cirrus
north thru east  
Temperature: 63F, Dew point: 41F, Wind: SW at 8 kts,
Wind: direction variable S-W
Sea-level pressure: 30.35 inches Hg, falling
Visibility: 80 miles
BHO SA 1455 CLR 80 278/63/41/2208/035/ LINE CU DSNT SSE NR HRZN
THN CI N-E/ WND 17V26/ 8/101 50001
 
WEATHER SUMMARY FOR SATURDAY, SEPTEMBER 19
 
TEMPERATURE (DEGREES F)
MAX.....65    NORMAL.....70
MIN.....45    NORMAL.....52
MEAN....55    NORMAL.....61
 
DEPARTURE FROM 30-YEAR AVERAGE...........-6
TOTAL DEPARTURE FOR THE MONTH...........-31 [-1.8 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............10  DEPARTURE.......+5
TOTAL HEATING UNITS FOR THE MONTH............67  DEPARTURE.......+4
TOTAL HEATING UNITS FOR THE SEASON..........101  DEPARTURE.......+7
TOTAL HEATING UNITS LAST SEASON TO DATE......59  DIFFERENCE.....+42
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY.............30 NW   AT 10:02 A.M. *
                   AEROVANE..............28 WNW  AT  8:00 A.M.
                   ASOS..................29 WNW  AT  8:26 A.M. 
                   DAVIS................ 31 WNW  AT  7:59 A.M. 
FASTEST MILE FOR YESTERDAY...............20 WNW  AT  8:09 A.M. 
MAXIMUM 2-MINUTE ASOS AVERAGE............21 WNW  AT  8:10 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE...........23 WNW  AT  8:10 A.M. 
AVERAGE WIND SPEED AND DIRECTION.......11.5 WNW
                   ASOS................11.0
                   DAVIS...............12.3 WNW [300 DEG]
* Last of several occurrences.
 
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 MONTH..............2.29   DEPARTURE....-0.30
                         ASOS..............2.33
TOTAL PRECIPITATION FOR THE YEAR..........37.06   DEPARTURE....+1.00
                         ASOS.............38.25
 
PRELIMINARY CLIMATE SUMMARY FOR SEPTEMBER 2009 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  71/51/61/-6/0/773/98     17 NW
9/2  76/54/65/-1/0/786/100    22 S
9/3  77/56/67/+1/0/587/75     19 SW
9/4  77/60/69/+3/0/764/98     18 NE
9/5  81/59/70/+5/0/591/76     25 NNW
9/6  64/53/59/-6/0/743/96     31 NNE
9/7  70/52/61/-4/0/709/92     20 WSW
9/8  75/56/66/+1/0/369/48     18 WSW  
9/9  68/55/62/-2/0/352/46     36 NNE  AERO 33 MPH NNE
9/10 65/53/59/-5/0/603/79     31 ENE
9/11 61/54/58/-6/0.49/000/00  30 NE
9/12 63/60/62/-1/1.74/000/00  30 NNE
9/13 76/58/67/+4/0.06/393/52  28 NW 
9/14 74/55/65/+2/0/699/93     22 WSW
9/15 75/56/66/+4/0/.../..     22 WNW
9/16 61/53/57/-5/T/.../..     31 NNE
9/17 60/49/55/-7/0/.../..     27 N   
9/18 71/47/59/-2/T/.../..     35 WSW  AERO 30 MPH WSW
9/19 65/45/55/-6/0/.../..     30 NW   AERO 28 MPH WNW
 
9/20 our morning low temp: 45F; the normal low is now 52F
 
NEW DAILY RECORDS FOR SEPTEMBER 2009 TO DATE...
None.
 
DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR SEPTEMBER 20
HIGH 90F IN 1983
LOW 34F IN 1979
PRE 4.57 INS IN 1899
WIND 44 MPH NE IN 1972
 
RECORDS FOR SEPTEMBER 21
HIGH 91 IN 1895
LOW 35 IN 1929, 1956, 1962
PRE 5.58 INS IN 1961 (HURRICANE ESTHER; RETURNED AS TS SEPT 25-26TH)
WIND 186 MPH S IN 1938 (GREAT NEW ENGLAND HURRICANE; CALCULATED GUST, STATION RECORD)
 
TODAY'S REPORT PREPARED BY: Robert Skilling