BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
WEDNESDAY, MAY 20, 2009 
ALL TIMES ARE IN EASTERN STANDARD TIME
 
RAPIDLY RISING TEMPERATURES THIS MORNING
REACH 80 DEGREES BY EARLY THIS AFTERNOON
AIR CONTINUES VERY DRY WITH RELATIVE HUMIDITY
DOWN UNDER 30% BY THIS AFTERNOON
 
Starting off from a near normal low temperature
of 49F this morning the thermometer has risen
rapidly today to 81F by early afternoon. The air
continues dry again today with relative humidity
down in 20% range like it was yesterday.
High cirrus clouds have spread across the sky going
from thin cirrus this morning to sheaves of
dense cirrus this afternoon.
 
Today's observations:
 
7 A.M.  
Weather: High thin overcast cirrus 
Temperature: 57F, Dew point: 41F, Wind: SW at 8 kts
Sea-level pressure: 30.37 inches Hg, rising
Visibility: 40 miles, west-northwest 50 miles   
6-hour minimum temp: 49F
24-hour precipitation: 0.00 inch
BHO SA 1155 300 –BKN 40 283/57/41/2308/037/
THN K LYR ALG HRZN SSE-SW AND NW-NE
VSBY WNW 55 LGT HZ/ 8/001 51014 10057 20049
 
10 A.M.  
Weather: High thin overcast cirrus 
Temperature: 73F, Dew point: 39F, Wind: WSW at 8 kts,
Wind: direction variable SSW to W 
Sea-level pressure: 30.37 inches Hg, steady
Visibility: 40 miles, northeast thru southeast
30 miles, west to northwest 50 miles, light haze      
BHO SA 1455 250 –OVC 40 284/73/39/2508/037/
LGT HZ VSBY NE-SE 30 W-NW 50 WND 21V28/ 8/001 51001
 
1 P.M.  
Weather: Broken dense cirrus clouds, higher cirrus
clouds partly thin and small breaks in overcast 
Temperature: 79F, Dew point: 42F, Wind: WSW at 7 kts,
Wind: direction variable SSW to WNW
Sea-level pressure: 30.35 inches Hg, falling
Visibility: 50 miles, NE-SE 35 miles light haze
in all quadrants  
6-hour maximum temp: 81F  
BHO SA 1755 200 SCT E220 BKN 250 OVC 50 278/79/42/2407/035/
ACSL ALQDS DENS CI ALQDS THN SPTS AND SML BINOVC LGT HZ
VSBY NE-SE 35 WND 21V29/ 8/042 58006 10081 20057   
 
WEATHER SUMMARY FOR TUESDAY, MAY 19
 
TEMPERATURE (DEGREES F)
MAX.....70    NORMAL.....68
MIN.....42    NORMAL.....48
MEAN....56    NORMAL.....58
 
DEPARTURE FROM 30-YEAR NORMAL...........-2
TOTAL DEPARTURE FOR THE MONTH..........+32 [+1.5 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............ 9  DEPARTURE.......+1
TOTAL HEATING UNITS FOR THE MONTH...........157  DEPARTURE......-41
TOTAL HEATING UNITS FOR THE SEASON.........6053  DEPARTURE.....-171
TOTAL HEATING UNITS LAST SEASON TO DATE....5837  DIFFERENCE....+216
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY............28 S   AT  7:25 P.M.
                   AEROVANE.............24 S   AT  5:37 P.M.  
                   ASOS.................24 SSW AT  9:16 P.M.  
                   DAVIS................27 S   AT  5:43 P.M.  
FASTEST MILE FOR YESTERDAY..............19 SSW AT  9:17 P.M.
MAXIMUM 2-MINUTE ASOS AVERAGE...........20 SSW AT  9:17 P.M.  
MAXIMUM 2-MINUTE DAVIS AVERAGE..........21 SSW AT  9:17 P.M. 
AVERAGE WIND SPEED AND DIRECTION.......10.3 WNW  
                   ASOS................10.4
                   DAVIS...............10.2 WSW [240 DEG]
 
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....+0.05
                         ASOS..............2.37 
TOTAL PRECIPITATION FOR THE YEAR..........16.99  DEPARTURE....-3.29
                         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/+4/0/457/52          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/.../..      27 NE   
5/19 70/42/56/-2/0/.../..          28 S 
 
5/20 our morning low temp: 49F; the normal low is now 48F
 
* correction to precip on 9th: was 0.13 in. should be 0.14 in.  
 
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 20
HIGH 91F IN 1975,1996
LOW 37F IN 1948, 2002
PRECIP 1.65 INCHES IN 1969
PEAK GUST 57 MPH S IN 1963, WNW IN 1982
 
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
 
TODAY'S REPORT PREPARED BY: Robert Skilling