BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
THURSDAY, MAY 21, 2009 
ALL TIMES ARE IN EASTERN STANDARD TIME
 
TEMPERATURES REACH UPPER 80'S EARLY AFTERNOON
EXTREMELY DRY AIR WITH RELATIVE HUMIDITY AT 15%
GUSTY SOUTH-SOUTHWEST WINDS OVER 30 MPH
 
Today's record high temperature is 92F in 1921
and that is quite likely out of reach although
we might come close to the 90-degree mark. 
Along with bright sunshine today an increasingly
warm airmass was bringing temperatures up into
the high 80's by early afternoon. The maximum had
reached 88F by 2 p.m. However, the air was extremely
dry with dew points down into the mid-30's and a
relative humidity measured at a very low 15% early
this afternoon.  Winds have been increasing from
the south-southwest and gusts have reached past
30 MPH at times with sustained speeds of 25 MPH.   
 
Today's observations:
 
7 A.M.  
Weather: Clear, few cirrus NW-N and NE-E and distant south 
Temperature: 65F, Dew point: 46F, Wind: SSW at 12 kts
Sea-level pressure: 30.25 inches Hg, rising
Visibility: 35 miles, west-northwest 45 miles, higher
above an inversion    
6-hour minimum temp: 59F
24-hour precipitation: 0.00 inch
BHO SA 1155 CLR 35 245/65/46/2112/025/ FEW CI NW-N AND NE-E
AND DSNT S VSBY WNW 45 AND HIER ABV INVSN 
THN K LYR ALG HRZN S-W-N LGT HZ/ 8/001 51005 10065 20059  
 
10 A.M.  
Weather: Thin broken cirrus clouds  
Temperature: 81F, Dew point: 39F, Wind: SW at 13G22 kts,
Wind: direction variable S to WSW 
Sea-level pressure: 30.23 inches Hg, falling
Visibility: 35 miles, WNW 45 miles, light haze increasing
BHO SA 1455 250 –SCT 300 –BKN 35 237/81/39/2213G22/023/
VSBY WNW 45 LGT HZ INCRSNG WND 19V25/ 8/001 58008
 
1 P.M.  
Weather: High thin scattered cirrus 
Temperature: 87F, Dew point: 34F, Wind: SSW at 16G25 kts,
Wind: Peak wind gust 27 kts SSW at 12:20 P.M.
Wind: Direction variable S to WSW
Sea-level pressure: 30.16 inches Hg, falling
Visibility: 35 miles, WNW 45 miles, light haze  
6-hour maximum temp: 88F  
BHO SA 1755 300 –SCT 35 214/87/34/2116G25/016/ VSBY WNW 45
LGT HZ ALQDS PK WND 2027/20/ WND 18V25/ 8/001 58023 10088
20065
 
WEATHER SUMMARY FOR WEDNESDAY, MAY 20
 
TEMPERATURE (DEGREES F)
MAX.....82    NORMAL.....68
MIN.....49    NORMAL.....48
MEAN....66    NORMAL.....58
 
DEPARTURE FROM 30-YEAR NORMAL...........+8
TOTAL DEPARTURE FOR THE MONTH..........+40 [+1.8 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............ 0  DEPARTURE.......-7
TOTAL HEATING UNITS FOR THE MONTH...........157  DEPARTURE......-48
TOTAL HEATING UNITS FOR THE SEASON.........6053  DEPARTURE.....-178
TOTAL HEATING UNITS LAST SEASON TO DATE....5849  DIFFERENCE....+204
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY............31 SSW AT 10:27 P.M. *
                   AEROVANE.............28 SSW AT 10:37 P.M. *   
                   ASOS.................29 SSW AT 10:37 P.M.   
                   DAVIS................32 SSW AT 10:26 P.M.   
FASTEST MILE FOR YESTERDAY..............23 SSW AT 10:19 P.M. 
MAXIMUM 2-MINUTE ASOS AVERAGE...........22 SSW AT 10:21 P.M.    
MAXIMUM 2-MINUTE DAVIS AVERAGE..........24 SW  AT 10:37 P.M.  
AVERAGE WIND SPEED AND DIRECTION.......12.6 SSW   
                   ASOS................12.7
                   DAVIS...............12.4 SSW [210 DEG]
 
* last of several occurrences....
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.00  DEPARTURE....-0.12
                         ASOS..............0.00
TOTAL PRECIPITATION FOR THE MONTH..........2.38  DEPARTURE....-0.07
                         ASOS..............2.37 
TOTAL PRECIPITATION FOR THE YEAR..........16.99  DEPARTURE....-3.41
                         ASOS.............18.05 
 
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/+8/0.14/104/12       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/-2/0/696/80          22 ENE
5/13 70/45/58/+2/0/732/84          31 SSE   AERO 29 MPH SSE
5/14 62/47/55/-2/0.10/166/19       53 S     AERO 52 MPH S
5/15 76/54/65/+8/0/474/54          38 S     AERO 38 MPH S
5/16 68/54/61/+4/T/457/52  *       35 S     AERO 35 MPH S
5/17 61/49/55/-2/0.09/009/01       35 WNW   AERO 33 MPH WNW
5/18 53/42/48/-10/0.04/168/19      27 NE   
5/19 70/42/56/-2/0/813/92          28 S 
5/20 82/49/66/+8/0/.../..          31 SSW
 
5/21 our morning low temp: 59F; the normal low is now 49F
 
* correction made on 16th; trace of rain added (shower evening)
 
 
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 21
HIGH 92F IN 1921
LOW 35F IN 1907
PRECIP 1.61 INS IN 1954
PEAK GUST 74 MPH WSW IN 2006
 
RECORDS FOR MAY 22
HIGH 93F IN 1911
LOW 35F IN 1907
PRECIP 3.75 INCHES IN 1920
PEAK GUST 49e MPH SSW IN 1947
 
TODAY'S REPORT PREPARED BY: Robert Skilling