BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY MONDAY, MAY 13, 2013 ALL TIMES ARE IN EASTERN STANDARD TIME VERY COOL AIR MASS IN PLACE TODAY AS DEW POINTS FALL INTO 20'S AND HIGH TEMPS. ARE HELD TO HIGH 50'S NORMAL AVERAGE HIGH TEMPERATURE IS NOW 66F The new chilly Canadian air mass which began arriving yesterday and continued to advect in overnight has brought much cooler and drier air today. There is a threat of frost or light freezing temperatures developing overnight tonight in the low lying areas. We're not likely to reach our record low of 33 degrees set here on the summit on , May 14, 1895. There is well below freezing air just 5000 feet up with Mt. Washington reporting temperatures in the the low 20's early this afternoon. Today's observations: 7 A.M. Weather: Clear, stratocumulus, few cumulus distant W-N, few cirrus in all quadrants Temperature: 46F; Dew Point: 30F; Wind: W at 10 kts Sea-level pressure: 29.94 ins. Hg, rising then more slowly Visibility: 55 miles, distant haze 6-hour min. temp: 41F 24-hour precip: 0.03 inch BHO SA 1155 CLR 55 139/46/30/2610/994/ SC LYR/FEW SML CU DSNT W-N FEW CI ALQDS DSNT HZ WND 23V29/ 8/801 51015 MANUAL 70003 ASOS 70002 10047 20041 10 A.M. Weather: Scattered cumulus, scattered cirrus Temperature: 53F; Dew Point: 30F; Wind: WSW at 10 kts, Wind: Direction variability SW-WNW, Wind: Gust to 18 kts past hour Sea-level pressure: 29.97 ins. Hg, rising then more rapidly Visibility: 55 miles, distant haze BHO SA 1455 55 SCT 250 SCT 55 148/53/30/2510/997/ DSNT HZ GST 18 KTS PST HR WND 23V29/ 8/101 53009 1 P.M. Weather: Scattered cumulus, moderate cumulus, stratocumulus formed by the spreading out of cumulus, scattered cirrus Temperature: 56F; Dew Point: 29F; Wind: W at 10G18 kts, Wind: Direction variability SW-WNW, Sea-level pressure: 29.96 ins. Hg, falling slightly Visibility: 60 miles, except 70 miles NW, distant haze BHO SA 1755 60 SCT 250 SCT 60 144/56/29/2610G18/996/ FEW MDT CU/SCCU VSBY NW 70 DSNT HZ WND 22V30/ 8/401 56004 10058 20046 WEATHER SUMMARY FOR SUNDAY, MAY 12, 2013 MOTHERS DAY TEMPERATURE (DEGREES F) MAX.....70 NORMAL.....65 MIN.....47 NORMAL.....47 MEAN....59 NORMAL.....56 DEPARTURE FROM 30-YEAR NORMAL....................+3 TOTAL DEPARTURE FOR THE MONTH...................+35 [+2.7 DEGREE/DAY] HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY.............6 DEPARTURE..........-4 TOTAL HEATING UNITS FOR THE MONTH............93 DEPARTURE.........-40 TOTAL HEATING UNITS FOR THE SEASON.........5615 DEPARTURE........-552 TOTAL HEATING UNITS LAST SEASON TO DATE....4859 DIFFERENCE.......+756 PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY...............30 W AT 6:37 P.M. AERO....................32 W AT 6:37 P.M. ASOS....................33 W AT 6:34 P.M. DAVIS...................29 WNW AT 4:46 P.M. RMY: 32 THE FASTEST MILE FOR YESTERDAY.............24 W AT 6:33 P.M. MAXIMUM 2-MINUTE ASOS AVERAGE..............24 W AT 6:34 P.M. MAXIMUM 2-MINUTE DAVIS AVERAGE.............21 W AT 6:34 P.M. AVERAGE WIND SPEED AND DIRECTION.........11.7 W ASOS..................11.7 DAVIS.................10.4 WSW [250 deg] PRECIPITATION (INCHES) THROUGH THIS MORNING (EST) TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.03 DEPARTURE............-0.10 ASOS..............0.02 TOTAL PRECIPITATION FOR THE MONTH..........0.94 DEPARTURE...........-0.53 ASOS..............0.89 TOTAL PRECIPITATION FOR THE YEAR..........17.32 DEPARTURE...........-2.70 ASOS..............N/A* *ASOS malfunctioned during storm on 2/8-9, leading to erroneous totals 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.............0.0 TOTAL SNOWFALL FOR THE SEASON.............99.0 DEPARTURE...........+36.3 PRELIMINARY CLIMATE SUMMARY FOR MAY 2013 CALENDAR DAY DATA DATA REPORTED: DATE: MAX/MIN/MEAN/DEP/PRECIP/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST AERO: Aerovane wind recording system gust RMY: RMY = R.M. Young wind gust recording system added 8/9/2011 TSTM: Thunderstorm day (thunder heard some time during day) ....: Data not yet available, records not finalized 5/1 67/45/56/+3/0.00/845/100 18 E AERO 16 MPH E RMY 17 5/2 75/43/59/+6/T/669/79 29 NE AERO 26 MPH NE RMY 29 5/3 54/42/48/-5/0.00/706/83 24 NE AERO 25 MPH NE RMY 28 5/4 55/40/48/-6/0.00/843/99 21 NE AERO 23 MPH NE RMY 23 5/5 58/37/48/-6/0.00/752/88 17 ENE AERO 17 MPH ENE RMY 20 5/6 66/40/53/-1/0.00/.../.. 17 S AERO 18 MPH S RMY 20 5/7 77/50/64/+9/0.00/.../.. 21 S AERO 23 MPH S RMY 25 5/8 71/55/63/+8/0.42/.../.. 31 SSE AERO 35 MPH SSE RMY 35 TSTM 5/9 66/56/61/+6/0.41/.../.. 16 NE AERO 16 MPH NE RMY 18 TSTM 5/10 79/54/66/+11/T/.../.. 18 S AERO 21 MPH S RMY N/A 5/11 70/56/63/+7/0.06/.../.. 43 SSW AERO 44 MPH SSW RMY 46 5/12 71/47/59/+3/0.05/339/39 30 W AERO 32 MPH W RMY 32 5/13 morning low temp: 41F; the normal low is now 47F DAILY RECORDS FOR MAY 2013 None so far. DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated): 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 RECORDS FOR MAY 14 HIGH 85F IN 1961 LOW 33F IN 1895 PRECIP 1.93 INCHES IN 2006 PEAK GUST 53 MPH S IN 2009 TODAY'S REPORT PREPARED BY: Robert Skilling