BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
SUNDAY, SEPTEMBER 20, 2015
ALL TIMES ARE IN EASTERN STANDARD TIME
 
AFTER A WARM NIGHT COLD FRONT FINALLY PASSES THIS MORNING
JUST A FEW DROPS OF RAIN ALONG THE FRONT
HUMIDITY DROPS SHARPLY--DEW POINTS GO FROM MID 60'S TO 50'S
 
A cooling trend has begun today after a weak cold frontal
passage this morning. Yesterday was the end of a very warm
for September stretch of temperatures. Along with the cooling
trend has come a sharp drop in the humidity best observed by
the change in dew point.  The dew point was in the 60's over-
night and dropped into and down into the 50's after the frontal
passage this morning.
Only a few drops of rainfall occurred this morning as the cold
front passed over us.  This continues to be a very dry September
with the precipitation total of only 1.35 inches running over
one inch below normal.  The total for the year is nearing 6 inches
below normal now at 31.60 inches.
 
Today's Observations:
 
7 A.M.
Weather: Overcast nimbostratus, few stratus fractus and stratocumulus,
break in overcast distant W-NNW, with line of clearing
Temperature: 68F; Dew Point: 66F; Wind: NW at 7 kts,
Wind: Gradually veering, apparent cold frontal passage 
Sea-level pressure: 29.92 ins. Hg, rising then more slowly
Visibility: 30 miles, hazy, except 45 miles WNW
6-hr Max temp: 68F 
6-hr Min temp: 65F
24-hr precip: trace
BHO SA 1155 E28 OVC 30 133/68/66/2809/992/ FEW SC/STFRA
BINOVC/LINE CLRG DSNT W=NNW VSBY WNW 45 WND GRDLY VEERING
APRNT COFROPA RB00E05/ 8/72/ 51020 MANUAL 6000/ 10068 2065
 
10 A.M.
Weather: Scattered Cumulus, stratocumulus, scattered altocumulus,
few lenticularis, scattered cirrus
Temperature: 72F; Dew Point 56F; Wind: NW at 7 kts,
Wind:Direction variable W-NNW
Sea-level pressure: 29.99 ins. Hg, rising, then more slowy
Visibility: 80 miles
BHO SA 1455 28 SCT 38 SCT 80 SCT 250 SCT 80 155/72/56/3207/999/
PTCH ACSL VC NW WND 27V34/ 8/841 51022
 
1 P.M.
Weather: Clear, cumulus distant ESE-S, distant altocumulus/lenticulris, NE-S,
few cirrus vicinity NE-S and distant S               
Temperature: 73F; Dew Point: 50F; Wind: NNW 9 kts
Sea-level pressure: 30.00 ins. Hg, rising then falling slightly
Visibility: 80 miles
6-hr Max: 74F
6-hr Min: 68F
BHO SA 1755 CLR 80 158/73/50/3309/000/ CU DSNT ESE-S AC/ACSL DSNT NE-S
CI FEW VC NE-S AND DSNT SE-S/ 8/141 50003 10074 20068
 
SUMMARY FOR SATURDAY, SEPTEMBER 19, 2015
  
TEMPERATURE (DEGREES F)
MAX.....80   NORMAL.....71
MIN.....62   NORMAL.....54
MEAN....71   NORMAL.....62
 
DEPARTURE FROM 30-YEAR NORMAL........................+9
TOTAL DEPARTURE FOR THE MONTH......................+122  [+6.2 DEGREES/DAY]

COOLING DEGREE DAYS (SEASON JAN TO DEC)
TOTAL COOLING UNITS FOR YESTERDAY...............6   DEPARTURE..........+5
TOTAL COOLING UNITS FOR THE MONTH.............131   DEPARTURE.........+82
TOTAL COOLING UNITS FOR THE SEASON............797   DEPARTURE........+211
TOTAL COOLING UNITS LAST SEASON TO DATE.......565   DIFFERENCE.......+232

PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY...................22  S   AT 4:56 P.M. *
                   ASOS........................22  SSW AT 3:59 P.M.   
                   DAVIS.......................22  SSW AT 1:10 P.M. RMY N/A
FASTEST MILE FOR YESTERDAY.....................N/A
MAXIMUM 2-MINUTE ASOS AVERAGE..................17  S   AT  8:21 P.M.   
MAXIMUM 2-MINUTE DAVIS AVERAGE.................16  S   AT 12:21 P.M.   
AVERAGE WIND SPEED AND DIRECTION..............10.6 SSW
                   ASOS.......................11.4 
                   DAVIS...................... 9.7 SSW [210 DEG]
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M.....trace DEPARTURE.....-0.14
                         ASOS...............0.00
TOTAL PRECIPITATION FOR THE MONTH...........1.35  DEPARTURE.....-1.09
                         ASOS...............1.33
TOTAL PRECIPITATION FOR THE YEAR...........31.60  DEPARTURE.....-5.85
                         ASOS................N/A ***
*** ASOS annual total not available due to erroneous readings
 
PRELIMINARY CLIMATE SUMMARY FOR SEPTEMBER CALENDAR DAY DATA
DATA REPORTED:
DATE: MAX/MIN/MEAN/DEP/PRECIP/SUN(MIN.)/SUN(%)/ PEAK GUST/RMY 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
 
9/1  81/65/73/+5/0.00/766/97               20 SSW RMY 20
9/2  89/64/77/+9/0.00/732/93               20 SW  RMY 21 
9/3  85/66/76/+9/T/612/78                  17 E   RMY N/A TSTM
9/4  72/58/65/0/0.00/297/38                31 ENE RMY N/A
9/5  77/55/66/-1/0.00/748/96               14 SW  RMY 18
9/6  87/57/72/+5/0.00/753/97               21 SSW RMY 22
9/7  92/63/78/+12/0.00/727/94              23 WSW RMY 24
9/8  97/70/84/+18/0.00/693/90              22 WSW RMY 24
9/9  92/70/81/+15/0.00/683/89              30 SSW RMY 33
9/10 73/62/68/+3/..../000/00               29 NE  RMY N/A
9/11 70/59/65/0/..../084/11                33 NE  RMY N/A
9/12 75/58/67/2/..../.../..                18 SSE RMY 25
9/13 66/60/63/-1/..../000/00               25 E   RMY N/A
9/14 70/53/62/-2/0.00/.../..               33 W   RMY 35
9/15 82/56/69/+5/0.00/.../..               23 W   RMY N/A
9/16 84/62/73/+10/0.00/.../..              17 NW  RMY N/A
9/17 87/64/76/+13/0.00/.../..              17 SW  RMY 16
9/18 86/64/75/+13/0.00/.../..              21 SSW RMY 21
9/19 80/62/71/+9/0.00/.../..               22 S   RMY N/A
 
9/20 low since midnight is 65F; normal low is now 53F 
 
DAILY RECORDS FOR SEPTEMBER 2015
 
**9/7 DAILY RECORD MAXIMUM TEMPERATURE OF 92F
TIES PREVIOUS RECORD SET IN 2007**
 
**9/8 DAILY RECORD MAXIMUM TEMPERATURE OF 97F
BREAKS PREVIOUS RECORD OF 93F SET IN 2007**
 
**9/8 DAILY RECORD HIGH MINIMUM TEMPERATURE OF 70F
BREAKS PREVIOUS RECORD OF 69F SET IN 1999**
 
**9/9 DAILY RECORD MAXIMUM TEMPERATURE OF 92F
BREAKS PREVIOUS RECORD OF 91F SET IN 2002**
 
**9/9 DAILY RECORD HIGH MINIMUM TEMPERATURE OF 70F
BREAKS PREVIOUS RECORD OF 69F SET IN 1999**
 
**9/17 DAILY RECORD MAXIMUM TEMPERATURE OF 87F
BREAKS PREVIOUS RECORD OF 86F SET IN 1915, 1941, AND 1991**
 
**9/18 DAILY RECORD HIGH MINIMUM TEMPERATURE OF 64F
TIES PREVIOUS RECORD SET IN 1992**
 
DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR SEPTEMBER 20
HIGH 90 IN 1983
LOW 34 IN 1979
PRECIP 4.57 INS IN 1899
PEAK GUST 44 MPH NE IN 1972
 
RECORDS FOR SEPTEMBER 21
HIGH 91 IN 1895
LOW 35 IN 1929, 1956, 1962
PRECIP 5.58 INS IN 1961 (HURRICANE ESTHER; RETURNED AS TS SEPT 25-26TH)
PEAK GUST 186 MPH S IN 1938 (GREAT NEW ENGLAND HURRICANE; CALCULATED GUST,
STATION RECORD)
 
TODAY'S REPORT PREPARED BY: Robert Skilling