BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS 02186 ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY SATURDAY, SEPTEMBER 19, 2009 ALL TIMES ARE IN EASTERN STANDARD TIME COOLEST TEMPERATURE OF THE SEASON THIS MORNING AT 45... SPECTACULAR VISIBILITY NEAR 80 MILES UNDER A SUNNY SKY... A cold front passed southward over New England on Friday evening, touching off a brief rain shower that left a trace of rain yesterday afternoon just after 5 PM EDT. Cooler, drier air moved in overnight, and the low temperature this morning of 45 was the coolest of the season to date. The dew point has dropped to the upper 30s this morning, and in the dry air the visibility has climbed to near or slightly better than 80 miles. There have been only a few distant clouds visible today. Today's observations: 7 A.M. Weather: Clear, few cumulus distant E-SE, few stratocumulus distant NW-NNE Temperature: 48F, Dew point: 39F, Wind: WNW at 10 kts Wind: Direction variable W-NW Sea-level pressure: 30.16 inches Hg, rising Visibility: 80 miles 6-hour minimum temp: 45F 24-hour precipitation: Trace BHO SA 1155 CLR 80 214/48/39/2910/016/ FEW CU DSNT E-SE FEW SC DSNT NW-NNE WND 26V32/ 8/500 53024 10051 20045 10 A.M. Weather: Clear, few cumulus distant ESE, few stratocumulus distant WNW-NNE Temperature: 56F, Dew point: 40F, Wind: NW at 15G23 kts Wind: Direction variable W-NNW Sea-level pressure: 30.19 inches Hg, rising Visibility: 80 miles BHO SA 1455 CLR 80 222/56/40/3115G23/019/ FEW CU DSNT ESE FEW SC DSNT WNW-NNE WND 27V34/ 8/500 50008 1 P.M. Weather: Thin scattered cirrus fibratus Temperature: 63F, Dew point: 39F, Wind: WNW at 10 kts Wind: Direction variable W-NNW Sea-level pressure: 30.18 inches Hg, falling Visibility: 80 miles 6-hour max. temp: 63F BHO SA 1755 250 –SCT 80 220/63/39/3010/018/ WND 27V33/ 8/001 58002 10063 20048 WEATHER SUMMARY FOR FRIDAY, SEPTEMBER 18 TEMPERATURE (DEGREES F) MAX.....71 NORMAL.....71 MIN.....47 NORMAL.....53 MEAN....59 NORMAL.....61 DEPARTURE FROM 30-YEAR AVERAGE...........-2 TOTAL DEPARTURE FOR THE MONTH...........-25 [-1.6 DEGREES/DAY] HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY.............6 DEPARTURE.......+1 TOTAL HEATING UNITS FOR THE MONTH............57 DEPARTURE.......-1 TOTAL HEATING UNITS FOR THE SEASON...........91 DEPARTURE.......+2 TOTAL HEATING UNITS LAST SEASON TO DATE......46 DIFFERENCE.....+45 PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY.............35 WSW AT 1:24 P.M. AEROVANE..............30 WSW AT 2:48 P.M. * ASOS..................33 W AT 2:48 P.M. DAVIS................ 34 SW AT 1:14 P.M. FASTEST MILE FOR YESTERDAY...............26 WSW AT 1:23 P.M. MAXIMUM 2-MINUTE ASOS AVERAGE............25 W AT 1:24 P.M. MAXIMUM 2-MINUTE DAVIS AVERAGE...........25 WSW AT 1:24 P.M. AVERAGE WIND SPEED AND DIRECTION.......14.3 WSW ASOS................13.8 DAVIS...............13.7 WSW [250 DEG] * Last of several occurrences. PRECIPITATION (INCHES) THROUGH THIS MORNING (EST) TOTAL PRECIPITATION 24 HRS ENDING 7 A.M...Trace DEPARTURE....-0.14 ASOS..............0.00 TOTAL PRECIPITATION FOR MONTH..............2.29 DEPARTURE....-0.16 ASOS..............2.33 TOTAL PRECIPITATION FOR THE YEAR..........37.06 DEPARTURE....+1.14 ASOS.............38.25 PRELIMINARY CLIMATE SUMMARY FOR SEPTEMBER 2009 CALENDAR DAY DATA DATA REPORTED: DATE: MAX/MIN/MEAN/DEP/PRECIP/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST AERO: Aerovane wind recording system gust when significant TSTM: Thunderstorm day (thunder heard some time during day) ....: Data not yet available, records not finalized 9/1 71/51/61/-6/0/773/98 17 NW 9/2 76/54/65/-1/0/786/100 22 S 9/3 77/56/67/+1/0/587/75 19 SW 9/4 77/60/69/+3/0/764/98 18 NE 9/5 81/59/70/+5/0/591/76 25 NNW 9/6 64/53/59/-6/0/743/96 31 NNE 9/7 70/52/61/-4/0/709/92 20 WSW 9/8 75/56/66/+1/0/369/48 18 WSW 9/9 68/55/62/-2/0/352/46 36 NNE AERO 33 MPH NNE 9/10 65/53/59/-5/0/603/79 31 ENE 9/11 61/54/58/-6/0.49/000/00 30 NE 9/12 63/60/62/-1/1.74/000/00 30 NNE 9/13 76/58/67/+4/0.06/393/52 28 NW 9/14 74/55/65/+2/0/699/93 22 WSW 9/15 75/56/66/+4/0/.../.. 22 WNW 9/16 61/53/57/-5/T/.../.. 31 NNE 9/17 60/49/55/-7/0/.../.. 27 N 9/18 71/47/59/-2/T/.../.. 35 WSW AERO 30 MPH WSW 9/19 morning low temp: 45F; the normal low is now 52F NEW DAILY RECORDS FOR SEPTEMBER 2009 TO DATE... None. DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated): RECORDS FOR SEPTEMBER 19 HIGH 87F IN 1906,1983 LOW 37F IN 1929 PRECIP 3.69 INCHES IN 1936 PEAK GUST 48 MPH NE IN 1972 RECORDS FOR SEPTEMBER 20 HIGH 90F IN 1983 LOW 34F IN 1979 PRE 4.57 INS IN 1899 WIND 44 MPH NE IN 1972 TODAY'S REPORT PREPARED BY: Mike Iacono