Saturday, May 20, 2017

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

DAILY DISCUSSION AND CLIMATE SUMMARY
SATURDAY, MAY 20, 2017
ALL TIMES ARE IN EASTERN STANDARD TIME

COLD FRONT PASSAGE FRIDAY EVENING BRINGS RETURN TO COOLER AIR…

After the record setting heat of the last few days, a cold front
crossed the area on Friday evening, which dropped the temperature
from the high of 89F at 1 PM EST yesterday (not a record) to 81F
at 6 PM, 64F at 9 PM, 56F at midnight and 51F before sunrise this
morning. Early morning mid-level clouds moved southward during the
morning leaving the sky mostly sunny with a few thin cirrus. The
high temperature has reached only the middle 60’s today. A peak
wind gust of 35 mph from the west during the early afternoon on
Friday has continued to diminish, and the wind has become light
and variable at mid-day today. Visibility has been very good at
70-75 mph all day, with a dew point in the low 30’s.

The high temperature of 96F on the 18th was not only a record for
the date and for the month of May, it was also the highest
temperature of 95F or more so early in the year, breaking the
previous occurrence of 95F or more, which was 98F on June 3, 1919.
The cumulative temperature departure over the last four days of +66
degrees has nearly erased all of the negative temperature departure
accumulated over the first 15 days of the month.

Today’s Observations:

7 A.M.
Weather: Broken altocumulus, few cumulus distant WNW-NW, few
cirrus NE, clearing line NW-NE moving south
Temperature: 53F; Dew Point: 35F; Wind: NNE at 9G17 kts
Sea-level pressure: 30.27 ins. Hg, rising then more slowly
Visibility: 75 miles, SSE-SW 60 miles
6-hr Max temp: 54F
6-hr Min temp: 51F
24-hr precip: 0.00 in.
BHO SA 1155 E120 BKN 75 251/53/35/0309G17/027/ FEW CU DSNT WNW-NW
FEW CI NE CLRNG NW-NE MVNG S VSBY SSE-SW 60/ 8/171 51028 10054 20051

10 A.M.
Weather: Scattered altocumulus, thin scattered cirrus
Temperature: 57F; Dew Point: 32F; Wind: ENE at 8 kts
Sea-level pressure: 30.29 ins. Hg, rising
Visibility: 75 miles
BHO SA 1455 140 SCT 220 -SCT 75 258/57/32/0708/029/ 8/031 50007

1 P.M.
Weather: Thin scattered cirrus
Temperature: 63F; Dew Point: 33F; Wind: N at 5 kts
Sea-level pressure: 30.29 ins. Hg, falling slightly
Visibility: 75 miles
6-hr Max temp: 64F
6-hr Min temp: 53F
BHO SA 1755 220 -BKN 75 256/63/33/3505/029/ FEW AC DSNT SE-SW
WND LGT AND VRB/ 8/031 58002 10064 20053

SUMMARY FOR FRIDAY, MAY 19, 2017

TEMPERATURE (DEGREES F)
MAX…..89   NORMAL…..67
MIN…..56   NORMAL…..49
MEAN….73   NORMAL…..58

DEPARTURE FROM 30-YEAR NORMAL……………………+15
TOTAL DEPARTURE FOR THE MONTH…………………….-2 [-0.3 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………0   DEPARTURE……….-8
TOTAL HEATING UNITS FOR THE MONTH………….220   DEPARTURE………+27
TOTAL HEATING UNITS FOR THE SEASON………..5553   DEPARTURE……..-675
TOTAL HEATING UNITS LAST SEASON TO DATE……5216   DIFFERENCE…….+337

COOLING DEGREE DAYS (SEASON JAN TO DEC)
TOTAL COOLING UNITS FOR YESTERDAY……………8   DEPARTURE……….+7
TOTAL COOLING UNITS FOR THE MONTH…………..36   DEPARTURE………+28
TOTAL COOLING UNITS FOR THE SEASON………….56   DEPARTURE………+46
TOTAL COOLING UNITS LAST SEASON TO DATE………4   DIFFERENCE……..+52

PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY……………….35   W AT  1:13 P.M. *
AERO……………………33   W AT  1:13 P.M. *
ASOS……………………36   W AT 12:52 P.M.
DAVIS…………………..34 WSW AT  1:14 P.M. RMY 37
FASTEST MILE FOR YESTERDAY…………………28   W AT 12:52 P.M.
MAXIMUM 2-MINUTE ASOS AVERAGE………………24   W AT 14:38 P.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE……………..25   W AT 12:54 P.M.
AVERAGE WIND SPEED AND DIRECTION………….14.7   W
ASOS………………….13.8
DAVIS…………………12.7 WNW [283 deg.]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M….0.00  DEPARTURE……-0.14
ASOS…………..0.00
TOTAL PRECIPITATION FOR THE MONTH……….3.16  DEPARTURE……+0.81
ASOS…………..3.23
TOTAL PRECIPITATION FOR THE YEAR……….23.97  DEPARTURE……+3.07
ASOS……………N/A ***
*** ASOS annual total not available due to erroneous readings

PRELIMINARY CLIMATE SUMMARY FOR MAY CALENDAR DAY DATA
DATE: MAX/MIN/MEAN/DEP/PRECIP/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

5/1  50/43/47/-6/T/034/04                  21 N   AERO 18 N   RMY 22
5/2  65/42/54/+1/0.26/136/16               41 W   AERO 44 W   RMY 43
5/3  52/42/53/0/0.00/595/70                37 WNW*AERO 39 WNW RMY 40
5/4  65/40/53/-1/0.00/724/85               23 S   AERO 23 S   RMY 24
5/5  51/44/48/-6/0.73/000/00               28 E   AERO 28 E   RMY N/A
5/6  65/50/58/+4/0.23/094/11               46 SSE AERO 48 SSE RMY 49
5/7  63/47/55/0/T/670/78                   35 S   AERO 38 S   RMY 39
5/8  54/38/46/-9/T/224/26                  29 WSW AERO 29 WSW RMY 32
5/9  53/36/45/-10/T/251/29                 20 ESE AERO 17 ESE RMY 19
5/10 57/42/50/-5/0.00/225/26               17 NNE AERO 16 NW  RMY N/A
5/11 58/45/52/-4/0.00/443/51               23 NE* AERO 23 NE  RMY 23
5/12 57/41/49/-7/0.01/…/..               21 NE  AERO 20 NE  RMY 19
5/13 57/41/49/-7/0.19/…/..               24 ENE AERO 24 E   RMY N/A
5/14 47/43/45/-12/1.49/…/..              33 NNE AERO 36 N   RMY 36
5/15 58/43/51/-6/0.24/…/..               36 NNW AERO 40 NNW RMY 41
5/16 79/51/65/+8/0.00/…/..               26 WNW AREO 26 WNW RMY 29
5/17 90/60/75/+18/T/…/..                 32 SSE AERO 33 SW* RMY 34
5/18 96/69/83/+25/0.01/,,,/..              39 WNW AERO 41 WNW RMY 42 TSTM
5/19 89/56/73/+15/T/…/..                 35 W   AERO 33 W   RMY 37

5/20 Low temp since midnight is 51F; normal low is now 49F

DAILY RECORDS FOR MAY

5/17/17: DAILY RECORD MAXIMUM TEMPERATURE OF 90F,
BREAKS PREVIOUS RECORD OF 88F SET IN 1974
AND TIED IN 1977

5/17/17: DAILY RECORD HIGH MINIMUM TEMPERATURE OF 60F,
TIES PREVIOUS RECORD SET IN 1932

5/18/17: DAILY RECORD MAXIMUM TEMPERATURE OF 96F,
BREAKS PREVIOUS RECORD OF 88F SET IN 1906
AND TIED IN 1936 AND 1986;
BREAKS PREVIOUS MONTHLY RECORD OF 94F SET ON
MAY 26, 2010

5/18/17: DAILY RECORD HIGH MINIMUM TEMPERATURE OF 69F,
BREAKS PREVIOUS RECORD OF 61F SET IN 1943

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: Mike Iacono