BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA

DAILY DISCUSSION AND CLIMATE SUMMARY
TUESDAY, MAY 12, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

ANOTHER BELOW NORMAL AND BREEZY DAY UNDER PARTLY SUNNY SKIES...

Yesterday's rain totaled 0.22". While a lightning bolt was 
observed to the west late yesterday afternoon, thunder was not 
heard, thus we didn't record a thunderstorm day. At any rate,
the activity yesterday was associated with a cold front that
came through last night, which has set us up for today's 
below normal temperatures and blustery westerly breeze.

The day started clear, but it didn't take long for clouds to
pop with the "heating" of the day. Stratocumulus this morning
has transitioned to cumulus this afternoon.

The air mass continues to dry out this afternoon with dew
points dropping into the mid 20s. Definitely adds a chill to
the air.

The high so far today is 55F, this is 10 degrees below the 
daily normal high of 65F. The low since midnight is 37F,
which is 10 degrees below the daily normal low of 47F.

Here are some interesting stats on the cold air mass we 
just had this past weekend per our Chief Scientist Mike
Iacono..

The low temperature of 31F on Sunday was the latest freeze
(32F or less) since 32F on May 10, 1977 and the latest 31F
or lower since 30F on May 12, 1963.  The latest freeze on
record remains 30F on May 16, 1936.

Here is the rankings on latest freeze at Blue Hill..

BHO Latest Freezing Temperature, deg F (1885-2020):

1) 30F on 16 May 1936
2) 29F on 12 May 1907
   30F on 12 May 1963
4) 28F on 11 May 1900
   31F on 11 May 1907
   31F on 11 May 1913
   30F on 11 May 1923
8) 29F on 10 May 1900
   31F on 10 May 1902
   31F on 10 May 1947
   32F on 10 May 1966
   32F on 10 May 1977 
   31F on 10 May 2020 


PRELIMINARY STATS FOR APRIL 2020

TEMPERATURE, Deg. F
Avg. Max. 50.6 [-5.1]
Avg. Min. 35.8 [-1.9]
Mean      43.4 [-3.3]
24-hour corrected mean: 42.9
Max. for month: 63F on the 7th
Min. for month: 28F on the 1st

HEATING DEGREE DAYS
Total heating units:    648 [+97]
Total for the season:  5521 [-514]
Total for last season: 5900

PRECIPITATION, Inches
Total: 7.71 [+3.16]
Greatest in 24 hrs: N/A 

SNOWFALL, Inches
Total: 4.3 [+1.3]
Greatest in 24 hrs: 4.3 ins. on the 18th

WIND, mph
Avg. uncorrected wind speed: 13.9 mph
Avg. corrected wind speed:   14.3 mph
Prevailing wind direction:   W [24%]
Peak gust and direction:     79 S on the 13th

SUNSHINE:
Campbell-Stokes card minutes: 8358 minutes of possible 23250 or 36%
Astronomical total minutes: 8676 minutes of possible 24148 or 36%



Today's Observations:

7 A.M.
Weather: Clear, few stratocumulus distant SW-NW, few cirrus
distant W-N-E 
Temperature: 44F; Dew Point: 32F; Relative Humidity: 62%
Wind: WNW at 12G21 kts  
Sea-level pressure: 29.87 ins. Hg: rising, then more rapidly
Visibility: 60 miles
6-hr Max temp: 44F
6-hr Min temp: 37F
24-hr Precip:  0.22 ins.
24-hr Snowfall: 0.0 ins.
BHO SA 1155 CLR 60 115/44/32/3012G21/987/ FEW SC DSNT SW-NW
FEW CI DSNT W-N-E/ 8/501 53024 70022 10044 20037 

10 A.M.
Weather: Broken stratocumulus
Temperature: 48F; Dew Point: 30F; Relative Humidity: 49%
Wind: WNW at 13G22 kts
Sea-level pressure: 29.89 ins. Hg: falling, then rising
Visibility: 70 miles 
3-hr Precip:  0.00 ins.
3-hr Snowfall: 0.0 ins.
BHO SA 1455 E45 BKN 70 122/48/30/3013G22/989/ 8/500 53007

1 P.M.
Weather: Broken cumulus
Temperature: 54F; Dew Point: 27F; Relative Humidity: 34%
Wind: W at 17G26 kts, peak wind 29 kts at 12:36 P.M.
Sea-level pressure: 29.87 ins. Hg: falling, then rising
Visibility: 70 miles 
6-hr Max temp: 55F
6-hr Min temp: 44F
6-hr Precip:  0.00 ins.
6-hr Snowfall: 0.0 ins.
BHO SA 1755 E55 BKN 70 116/54/27/2817G26/987/ PK WND 2729/36/
8/100 55006 10055 20044

SUMMARY FOR MONDAY, MAY 11, 2020 

TEMPERATURE (DEGREES F)
MAX.....65   NORMAL.....65
MIN.....43   NORMAL.....46
MEAN....54   NORMAL.....56

DEPARTURE FROM 30-YEAR NORMAL.................. -2
TOTAL DEPARTURE FOR THE MONTH..................-23 [-2.3 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY...............11  DEPARTURE....... +1
TOTAL HEATING UNITS FOR THE MONTH..............143  DEPARTURE.......+20
TOTAL HEATING UNITS FOR THE SEASON............5664  DEPARTURE......-494
TOTAL HEATING UNITS LAST SEASON TO DATE.......6042  DEPARTURE......-378

COOLING DEGREE DAYS (SEASON JAN TO DEC)
TOTAL COOLING UNITS FOR YESTERDAY................0  DEPARTURE........ 0
TOTAL COOLING UNITS FOR THE MONTH................2  DEPARTURE........-1
TOTAL COOLING UNITS FOR THE SEASON...............2  DEPARTURE........-3
TOTAL COOLING UNITS LAST SEASON TO DATE..........0  DEPARTURE........+2

PEAK GUST AND AVERAGE WIND SPEED (MPH) 
PEAK WIND GUST FOR YESTERDAY....................39 S   AT 11:47 A.M.  
                   AERO.........................43 S   AT  5:34 P.M.  
                   ASOS.........................40 SSW AT  5:34 P.M. 
                   DAVIS........................43 S   AT 11:42 A.M. RMY 41
FASTEST MILE FOR YESTERDAY......................29 S   AT  1:58 P.M. 
MAXIMUM 2-MINUTE ASOS AVERAGE...................29 S   AT 11:47 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE..................28 S   AT 11:42 A.M.
AVERAGE WIND SPEED AND DIRECTION................13.2 S               
                   ASOS.........................13.2
                   DAVIS........................12.8 SSW [211 deg.]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.22  DEPARTURE......+0.09
                         ASOS..............0.21
TOTAL PRECIPITATION FOR THE MONTH..........1.61  DEPARTURE......+0.26
                         ASOS..............1.60
TOTAL PRECIPITATION FOR THE YEAR..........18.65  DEPARTURE......-1.25
                         ASOS.............19.20

SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M..........0.0  DEPARTURE........0.0
TOTAL SNOWFALL FOR THE MONTH..............Trace  DEPARTURE........0.0
TOTAL SNOWFALL FOR THE SEASON..............31.9  DEPARTURE......-30.8

PRELIMINARY CLIMATE SUMMARY FOR APRIL CALENDAR DAY DATA
DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN.)/SUN(%)/PEAK GUST/AERO/RMY GUST
AERO: Aerovane wind recording system gust
RMY:  R.M. Young wind gust recording system
TSTM: Thunderstorm day (thunder heard some time during day)
....: Data not yet available, records not finalized
M:    Missing data

04/01  42/28/35/-6/0.00/0.0/008/01         28 NE  AERO 28 NE  RMY 30
04/02  46/35/41/0/0.34/0.0/000/00          39 NW  AER0 40 NW  RMY 41
04/03  42/38/40/-2/2.14/0.0/000/00         48 NE  AERO 53 NE  RMY 49
04/04  46/36/41/-1/0.24/0.0/278/36         38 NE  AERO 38 NE  RMY N/A
04/05  55/36/46/+3/0.00/0.0/039/05         22 S   AERO 21 S   RMY 21
04/06  61/40/51/+8/0.00/0.0/732/94         29 NW  AERO 30 NW  RMY 29
04/07  63/42/53/+10/0.00/0.0/649/83        29 W   AERO 30 W   RMY 28
04/08  50/41/46/+2/0.08/T/047/06           23 S   AERO 22 S   RMY 22 
04/09  47/37/42/-2/0.66/T/000/00           58 W   AERO 58 W   RMY 56
04/10  47/35/41/-4/0.02/T/324/41           48 W   AERO 50 W   RMY 53 
04/11  51/33/42/-3/0.00/0.0/730/92         38 WNW AERO 39 WNW RMY 40
04/12  60/33/47/+2/0.00/0.0/326/41         38 S   AERO 40 S   RMY N/A
04/13  59/50/55/+9/1.42/0.0/000/00         79 S   AERO 83 S   RMY 78
04/14  57/41/49/+3/0.00/0.0/641/80         41 W   AERO 40 W   RMY N/A
04/15  52/36/44/-3/0.02/0.0/450/56         37 W   AERO 36 W   RMY 37
04/16  47/32/40/-7/T/T/379/47              33 WNW AERO 33 WNW RMY 32
04/17  49/29/39/-8/0.01/0.0/591/73         41 W   AERO 39 W   RMY 41
04/18  37/31/34/-14/0.73/4.3/000/00        29 NE  AERO 25 NE  RMY 25
04/19  60/31/46/-2/0.00/0.0/693/85         40 SSW AERO 40 SSW RMY 41
04/20  49/37/43/-6/0.00/0.0/000/00         25 ENE AERO 22 W   RMY N/A
04/21  53/33/43/-6/0.34/T/271/33         52 S   AERO 52 S   RMY 52
04/22  43/30/37/-12/0.00/0.0/601/73        51 W   AERO 50 W   RMY 50
04/23  55/29/42/-8/0.00/0.0/545/66         31 W   AERO 29 W   RMY N/A
04/24  42/37/40/-10/0.34/0.0/000/00        31 NNE AERO 29 NNE RMY 29
04/25  60/38/49/-1/0.00/0.0/557/67         25 S   AERO 24 S   RMY 24
04/26  51/38/45/-6/0.42/0.0/000/00         51 NE  AERO 50 NE  RMY 50
04/27  39/35/37/-14/0.94/T/000/00          54 NE  AERO 52 NNE RMY 55
04/28  48/35/42/-10/0.00/0.0/159/19        28 N   AERO 27 N   RMY N/A
04/29  55/35/45/-7/0.00/0.0/656/78         24 ENE AERO 23 ENE RMY 22
04/30  52/42/47/-5/0.01/0.0/000/00         36 SE  AERO 32 SE  RMY N/A

DAILY RECORDS FOR APRIL 2020

4/13/2020
NEW PEAK GUST OF 79 MPH S, REPLACING THE OLD
RECORD OF 59 MPH SSW IN 1995

4/18/2020
NEW RECORD SNOWFALL OF 4.3 INS, REPLACING THE OLD
RECORD OF 3.7 INS IN 1965

4/27/2020
NEW RECORD LOW MAX TEMPERATURE OF 39F, REPLACING
THE OLD RECORD OF 40F IN 1917

PRELIMINARY CLIMATE SUMMARY FOR MAY CALENDAR DAY DATA
DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN.)/SUN(%)/PEAK GUST/AERO/RMY GUST
AERO: Aerovane wind recording system gust
RMY:  R.M. Young wind gust recording system
TSTM: Thunderstorm day (thunder heard some time during day)
....: Data not yet available, records not finalized
M:    Missing data

05/01  64/52/58/+5/..../0.0/.../..         46 SSE  AERO 44 SSE RMY N/A 
05/02  70/42/56/+3/..../0.0/.../..         41 NW   AERO 40 NW  RMY N/A
05/03  78/55/67/+14/0.00/0.0/.../..        35 SSW  AERO 35 SSW RMY 36
05/04  72/45/59/+5/T/0.0/.../..            37 NW   AERO 40 WNW RMY 39  
05/05  60/40/50/-4/0.00/0.0/.../..         31 NW   AERO 32 NW  RMY N/A
05/06  57/38/48/-6/T/0.0/.../..            24 ESE  AERO 22 ENE RMY 22
05/07  63/37/50/-5/0.00/0.0/.../..         30 WSW  AERO 29 WSW RMY N/A
05/08  57/40/49/-6/..../0.0/.../..         31 W    AERO 32 W   RMY N/A
05/09  44/32/38/-17/..../T/.../..          52 W    AERO 53 W   RMY 54
05/10  59/31/45/-10/0.00/0.0/.../..        46 W    AERO 46 W   RMY 49
05/11  65/43/54/-2/0.22/0.0/.../..         39 S    AERO 43 S   RMY 41

05/12 The low since midnight is 37F, the daily normal low is 47F
 
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: Matt Douglas