BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
MONDAY, MAY 18, 2009 
ALL TIMES ARE IN EASTERN STANDARD TIME
 
A CLOUDY SKY TODAY AND A PERIOD OF LIGHT SHOWERS
VERY COOL WEATHER FOR MID-MAY WITH TEMP. IN 40'S
 
An overcast of low and middle clouds has shut out
all of our sunshine today at least through early
this afternoon.  A period of light rain showers
yielded 0.04 inch of precipitation over a three
hour period this morning. The heavy cloud cover
and light northeast wind have combined to hold
our temperatures in the 40's with the maximum
of just 49 degrees through early this afternoon. 
A maximum of 49F would be 19 degrees cooler than
the average for this date.  A low temperature of
42F occurred late this morning as the rain was
ending.  The record low maximum temperature for
this date is 42F in 2007.
 
Today's observations:
 
7 A.M.  
Weather: Overcast with altostratus and virga,
few stratocumulus, altocumulus east thru south
Temperature: 48F, Dew point: 35F, Wind: NNE at 6 kts
Sea-level pressure: 30.22 inches Hg, rising
Visibility: 55 miles
6-hour minimum temp: 45F
24-hour precipitation: 0.05 inch
BHO SA 1155 E130 OVC 55 234/48/35/0306/022/
FEW SC/AC E-S VIRGA ALQDS SUN DISC DMLY VSB/
8/52/ 53021 ASOS 70006 MANUAL 70005 10048 20045
 
10 A.M.  
Weather: Overcast nimbostratus, light rain
Temperature: 43F, Dew point: 39F, Wind: NNE at 8 kts 
Sea-level pressure: 30.26 inches Hg, rising
Visibility: 15 miles, northeast thru southeast 8 miles,
west thru northwest 50 miles
3-hourly rainfall: 0.03 inch
BHO SA 1455 E30 OVC 15R- 248/43/39/0308/026/
VSBY NE-SE 8 W-NW 50/ 8/02/ 53014 MANUAL 6003/
ASOS 60002
 
1 P.M.  
Weather: Scattered stratocumulus and altocumulus,
overcast altostratus  
Temperature: 47F, Dew point: 36F, Wind: ESE at 2 kts,
Wind: very light and variable (estimated)
Sea-level pressure: 30.27 inches Hg, rising
Visibility: 60 miles
6-hour maximum temp: 48F
6-hourly precip: 0.04 inch  
BHO SA 1755 25 SCT 85 SCT E140 OVC 60 249/47/36/E1202/027/
WND L/V 8/57/ 53001 ASOS 60003 MANUAL 6004/ 10048 20042
 
WEATHER SUMMARY FOR SUNDAY, MAY 17
 
TEMPERATURE (DEGREES F)
MAX.....61    NORMAL.....68
MIN.....49    NORMAL.....47
MEAN....55    NORMAL.....57
 
DEPARTURE FROM 30-YEAR NORMAL...........-2
TOTAL DEPARTURE FOR THE MONTH..........+44 [+2.4 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............10  DEPARTURE.......+2
TOTAL HEATING UNITS FOR THE MONTH...........131  DEPARTURE......-51
TOTAL HEATING UNITS FOR THE SEASON.........6027  DEPARTURE.....-181
TOTAL HEATING UNITS LAST SEASON TO DATE....5820  DIFFERENCE....+207
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY............35 WMW AT  8:38 A.M. *
                   AEROVANE.............33 WNW AT  8:38 A.M. 
                   ASOS.................33 SSE AT 12:57 A.M. 
                   DAVIS................36 WNW AT  8:38 A.M.
FASTEST MILE FOR YESTERDAY..............24 WNW AT  8:05 A.M. *
MAXIMUM 2-MINUTE ASOS AVERAGE...........24 S   AT  2:01 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE..........24 W   AT  8:39 A.M. **
AVERAGE WIND SPEED AND DIRECTION.......13.3 W
                   ASOS................12.5
                   DAVIS...............13.5 WSW [240 DEG]
*  last of several occurrences...
** time within the hour but minute estimated
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.05  DEPARTURE....-0.07
                         ASOS..............0.06
TOTAL PRECIPITATION FOR THE MONTH..........2.34  DEPARTURE....+0.25
                         ASOS..............2.34 
TOTAL PRECIPITATION FOR THE YEAR..........16.95  DEPARTURE....-3.09
                         ASOS.............18.02 
 
SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M..........0.0  DEPARTURE..... 0.0
TOTAL SNOWFALL FOR THE MONTH................0.0  DEPARTURE.....-0.1
TOTAL SNOWFALL FOR THE SEASON..............78.9  DEPARTURE.....18.8 
 
PRELIMINARY CLIMATE SUMMARY FOR MAY 2009 CALENDAR DAY DATA
DATA REPORTED:
DATE: MAX/MIN/MEAN/DEP/PRECIP/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST
AERO: Aerovane recording wind system gust when significant
TSTM: Thunderstorm day (thunder heard some time during day)
....: Data not yet available, records not finalized
 
5/1  64/53/59/+7/T/000/00          37 SSW   AERO 37 MPH SSW
5/2  68/52/60/+8/0.05/263/31       32 WNW
5/3  64/48/56/+3/T/068/08          25 S
5/4  64/48/56/+3/0.01/009/01       17 SSW
5/5  52/44/48/-5/0.95/000/00       43 NNE   AERO 40 MPH NNE
5/6  63/43/53/-1/0.40/189/22       24 SSE  
5/7  68/49/59/+5/0.60/009/01       29 S    
5/8  75/52/64/+10/0/690/80         28 S
5/9  71/55/63/+8/0.13/104/12       31 W     TSTM
5/10 65/46/56/+1/0/840/97          53 W     Aero 50 MPH W
5/11 63/41/52/-3/0/781/90          24 WNW
5/12 63/45/54/-2/0/.../..          22 ENE
5/13 70/45/58/+2/0/.../..          31 SSE   AERO 29 MPH SSE
5/14 62/47/55/-2/0.10/.../..       53 S     AERO 52 MPH S
5/15 76/54/65/+8/0/.../..          38 S     AERO 38 MPH S
5/16 68/54/61/+4/../.../..         35 S     AERO 35 MPH S
5/17 61/49/55/-2/0.09/009/01       35 WNW   AERO 33 MPH WNW
 
5/18 morning low temp: 45F; our normal low is now 48F
 
NEW DAILY RECORDS FOR MAY 2009...
5/14: RECORD PEAK WIND GUST 53 MPH S;
      surpasses previous record of 50 MPH SW in 1976
 
DAILY EXTREMES
 
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR MAY 18
HIGH 88F IN 1906, 1936, 1986
LOW 35F IN 2002
PRECIP 1.93 INS IN 2007
SNOW TRACE IN 2002 (Ice pellets)
PEAK GUST 64 MPH SSW IN 2000
 
RECORDS FOR MAY 19
HIGH 91F IN 1962
LOW 34F IN 2002
PRECIP 1.54 INCHES IN 1900
PEAK GUST 58 MPH NW IN 1964
 
TODAY'S REPORT PREPARED BY: Robert Skilling