BLUE HILL OBSERVATORY MILTON, MA
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
WEDNESDAY, SEPTEMBER 22, 2010
ALL TIMES ARE IN EASTERN STANDARD TIME
 
RISING TEMPERATURES OVERNIGHT LAST NIGHT AS A WARM AND
INCREASING HUMID LATE SUMMER AIR MASS ARRIVES ON THIS
LAST DAY OF SUMMER AS AUTUMN BEGINS THIS EVENING
 
An increasingly warm and summer-like humid air mass was
arriving today on south-southwest to southwest winds.
Wind speeds have been decreasing after reaching peak gusts
just over 30 MPH early this morning.  Temperatures have
reached the lower 80's (82F) by 2 PM EDT. Dew points
has climbed into the mid-60's giving the day the feel
of mid-summer.  In fact the last day with 80 degrees
was way back on September 8.
 
The autumnal equinox occurs at 11:09 PM EDT today marking the 
beginning of the fall season.  Today also marks the earliest 
freeze date(< or = 32F) recorded on the summit. This occurred 
in 1904.  The average date of the first freeze is October 19.  
The latest freeze was November 15, 1938.  Listed below are the 
dates of the first freeze for the past 5 years:
 
2009  Oct 14
2008  Oct 23
2007  Oct 29
2006  Oct 27
2005  Oct 29
 
Today's observations: 
 
7 A.M.
Weather: Clear, few cirrus
Temperature: 63F, Dew point: 58F; Wind: SSW at 15G25 kts,
Sea-level pressure: 30.02 inches Hg, falling 
Visibility: 35 miles, distant haze
6-hour minimum temp: 58F
BHO SA 1155 CLR 35 165/63/58/2015G25/002/ FEW CI DSNT HZ/
8/001 50002 10063 20058  
 
10 A.M.
Weather: Thin scattered cirrus
Temperature: 73F, Dew point: 61F; Wind: SSW at 18 kts,
Wind: Peak wind 27 kts SSW at 9:08 a.m.,
Wind: Direction variable S to WSW 
Sea-level pressure: 29.99 inches Hg, falling
Visibility: 30 miles, distant haze 
BHO SA 1455 250 –SCT 30 156/73/61/2018/999/ DSNT HZ INCR
PK WND 2127/08 WND 18V24/ 8/001 58009
 
1 P.M.  
Weather: Clear, few altocumulus lenticularis WSW-WNW,
few cirrus all quadrants
Temperature: 82F, Dew point: 64F; Wind: SW at 12 kts,
Wind: Gust to 19 kts past hour,
Wind: Direction variable S to WSW
Sea-level pressure: 29.97 inches Hg, falling
Visibility: 30 miles, distant haze
6-hourly max. temp: 82F
BHO SA 1755 CLR 30 148/82/64/2312/997/ FEW ACSL WSW-WNW
FEW CI ALQDS DSNT HZ GST TO 19 KTS PST HR WND 18V26/
8/041 58008 10082 20058
 
WEATHER SUMMARY FOR TUESDAY, SEPTEMBER 21
 
TEMPERATURE (DEGREES F)
MAX.....70     NORMAL.....69
MIN.....46     NORMAL.....51
MEAN....58     NORMAL.....60       
DEPARTURE FROM 30-YEAR NORMAL..............-2
TOTAL DEPARTURE FOR THE MONTH.............+39 [+1.7 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY.............7    DEPARTURE........+1
TOTAL HEATING UNITS FOR THE MONTH............57    DEPARTURE.......-17
TOTAL HEATING UNITS FOR THE SEASON...........70    DEPARTURE.......-35
TOTAL HEATING UNITS LAST SEASON TO DATE.....110    DIFFERENCE......-40
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY.............31 S   AT  8:34 P.M.
                   AEROVANE..............35 S   AT  8:13 P.M.  
                   ASOS..................35 S   AT 10:49 P.M.     
                   DAVIS.................34 SSW AT  8:34 P.M.    
THE FASTEST MILE FOR YESTERDAY...........24 S   AT  8:36 P.M.
MAXIMUM 2-MINUTE ASOS AVERAGE............24 SSW AT 11:59 P.M.    
MAXIMUM 2-MINUTE DAVIS AVERAGE...........26 S   AT  8:36 P.M. 
AVERAGE WIND SPEED AND DIRECTION.......13.5 SSW
                   ASOS................13.0
                   DAVIS...............13.4 WSW [235 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..........1.08  DEPARTURE........-1.79
                         ASOS..............1.05
TOTAL PRECIPITATION FOR THE YEAR..........47.11  DEPARTURE.......+10.77
                         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
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/.../..   28 W    AERO 31 MPH W
9/16 70/46/58/-4/0.26/.../..   43 S
9/17 68/53/61/-1/0.25/.../..   45 S
9/18 65/53/59/-2/0.00/.../..   15 SE
9/19 76/54/65/+4/T/.../.. **   17 SW   AERO 22 MPH SW
9/20 69/50/60/-1/0.00/.../..   29 NW   AERO 33 MPH NW
9/21 70/46/58/-2/0.00/.../..   31 S    AERO 35 MPH S
 
9/22 our morning low temp: 58F; the normal low is now 51F 
 
** trace of rain added to 19th...
 
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 22
HIGH 90F IN 1895, 1914
LOW 30F IN 1904 (Earliest freeze)
PRECIP 1.16 INCHES IN 2001
PEAK GUST 60 MPH SSW IN 1989
 
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
 
TODAY'S REPORT PREPARED BY: Robert Skilling