BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
TUESDAY, MAY 12, 2009 
ALL TIMES ARE IN EASTERN STANDARD TIME
 
THUNDERSTORMS WITH SOME SMALL HAIL DEVELOPED
OVER PARTS OF CT, RI, AND SE MASS.
BY EARLY THIS AFTERNOON
 
A line of towering cumulus clouds could been
seen developing this morning to our distant
south-southeast through south-southwest. 
By early afternoon this cloud area became
a line of cumulonimbus. More observations
revealed a line of showers and thunderstorms
had developed extending east-southeast from
Connecticut, across Rhode Island to the
southeastern portion of Massachusetts. The
activity was moving to the east-southeast or
to the southeast. There were reports of pea
to dime size hail from the vicinity of
Swansea, MA by 1 p.m.
 
A severe thunderstorm warning was issued
for southeastern CT.  Cold air aloft was
resulting in the convective weather and 
Mt. Washington reported below freezing
temperatures this morning.  
 
Today's observations:
 
7 A.M.  
Weather: Scattered  altocumulus clouds, virga NW-N
Temperature: 52F, Dew point: 43F, Wind: N at 7 kts,
Wind: direction variable northwest to northeast  
Sea-level pressure: 30.12 inches Hg, rising
Visibility: 20 miles, 15 miles NE-SE, 40 miles WNW
6-hour minimum temp: 45F
24-hour precipitation: 0.00
BHO SA 1155 90 SCT 20 198/52/43/3607/012/ VIRGA NW-N HAZY VSBY
NE-SE 15 WNW 40 WND 32V04/ 8/070 53020 10052 20045
 
10 A.M.  
Weather: Scattered altocumulus, few castellanus,
towering cumulus distant SSE-SSW, virga northwest  
Temperature: 58F, Dew point: 42F, Wind: NNE at 8G17 kts.
Wind: direction variable north-northwest to east-northeast
Sea-level pressure: 30.16 inches Hg, rising
Visibility: 50 miles 
BHO SA 1455 90 SCT 50 215/58/42/0308G17/016/ TCU SSE-SSW
CU/MDT CU FRMG SW-NW FEW ACC ALQDS VIRGA WNW-NW WND 34V07/
8/280 51017 
 
1 P.M.  
Weather: Scattered cumulus, moderate cumulus, altocumulus
lenticularis, cumulonimbus tops, cumulus except overhead
through northeast through east, cumulonimbus tops distant
southeast through south, virga distant SSE-SW
Temperature: 61F, Dew point: 33F, Wind: NE at 11G18 kts,
Wind: direction variable NNW to E 
Sea-level pressure: 30.17 inches Hg, steady
Visibility: 50 miles
6-hour maximum temp: 62F  
BHO SA 1755 50 SCT 120 SCT 200 SCT 50 217/61/33/0511G18/017/
CB TOPS DSNT SSE-S CU/MDT XCPT OVHD-NE-E FEW ACSL
VIRGA DSNT SSE-SW RWU DSNT SSE WND 34V08/
8/243 51002 10062 20052
 
WEATHER SUMMARY FOR MONDAY, MAY 11
 
TEMPERATURE (DEGREES F)
MAX.....63    NORMAL.....65
MIN.....41    NORMAL.....45
MEAN....52    NORMAL.....55
 
DEPARTURE FROM 30-YEAR NORMAL...........-3
TOTAL DEPARTURE FOR THE MONTH..........+36 [+3.1 DEGREES/DAY]
 
HEATING DEGREE DAYS
TOTAL HEATING UNITS FOR YESTERDAY............13  DEPARTURE.......+3
TOTAL HEATING UNITS FOR THE MONTH............89  DEPARTURE......-39
TOTAL HEATING UNITS FOR THE SEASON.........5985  DEPARTURE.....-169
TOTAL HEATING UNITS LAST SEASON TO DATE....5752  DIFFERENCE....+233
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY............24 WNW AT  7:19 A.M. * 
                   AEROVANE.............23 WNW AT  7:19 A.M. *
                   ASOS.................24 WNW AT  7:02 A.M.  
                   DAVIS................26 WNW AT  7:19 A.M. 
FASTEST MILE FOR YESTERDAY..............17 WNW AT  7:23 A.M. 
MAXIMUM 2-MINUTE ASOS AVERAGE...........18 WNW AT  7:25 A.M. 
MAXIMUM 2-MINUTE DAVIS AVERAGE..........19 W   AT  7:25 A.M. 
AVERAGE WIND SPEED AND DIRECTION......10.2 W 
                   ASOS................9.2
                   DAVIS..............10.2 WSW [250 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..........2.15  DEPARTURE....+0.78
                         ASOS..............2.14 
TOTAL PRECIPITATION FOR THE YEAR..........16.76  DEPARTURE....-2.56
                         ASOS.............17.82 
 
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/.../000/00        43 NNE   AERO 40 MPH NNE
5/6  63/43/53/-1/.../189/22        24 SSE  
5/7  68/49/59/+5/.../009/01        29 S    
5/8  75/52/64/+10/0/690/80         28 S
5/9  71/55/63/+8/.../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 morning low temp: 45F; our normal low is now 46F
 
* TSTM (thunderstorm day added 5/9)
 
NEW DAILY RECORDS FOR MAY 2009...
NONE
 
DAILY EXTREMES
 
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR MAY 12
HIGH 88F IN 2001
LOW 29F IN 1907
PRECIP 1.49 INCHES IN 1968
PEAK GUST 76 MPH S IN 1974
 
RECORDS FOR MAY 13
HIGH 85F IN 1947
LOW 35F IN 1914, 2005
PRECIP 2.39 INCHES IN 2006
PEAK GUST 49 MPH NNW IN 1965
 
TODAY'S REPORT PREPARED BY: Robert Skilling