BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS 02186 ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY FRIDAY, DECEMBER 18, 2009 ALL TIMES ARE IN EASTERN STANDARD TIME TEMPERATURES MODERATE AFTER VERY COLD 24 HOURS ANOTHER VERY SUNNY DAY DURING A SUNNY MONTH Under completely sunny skies the very cold Arctic air mass began to moderate today with temperatures reaching the mid-20's by early afternoon. At the same time the air was extremely dry with a dew point of -5F and relative humidity down to 26%. This morning's low temp. of 6F (5.5) occurred before dawn and was our coldest since 6F last March 4th. Snow making at the ski area began yesterday and was going full blast all of last night. The ski area expects to open this weekend. A few small patches of natural snow can be seen around the summit but a lot of man-made snow has accumulated as a very thin spotty cover. Ponkapoag Pond appears to have frozen over for a second time this month while Houghtons has only 2 ot 3/10's of ice cover. Yesterday (and probably today too) was the 2nd of two days with 100% of the possible bright sunshine this month bringing the monthly average percent up to 60 or well above the norm for December which is 46%. Today's observations: 7 A.M. Weather: Clear, stratocumulus offshore NE-SE, few altocumulus and altocumulus lenticularis S-NW Temperature: 7F, Dew point: -4F, Wind: WNW at 17G25 kts, Wind: Peak wind gust 29 kts from WNW at 6:15 a.m., Windchill: -13F Sea-level pressure: 30.19 inches Hg, rising Visibility: 70 miles 6-hour minimum temp: 6F 24-hour precipitation: 0.00 24-hour snowfall: 0.00 Average snow depth: none BHO SA 1155 CLR 70 225/7/-4/2918G23/019/ SC LYR OFFSHR DSNT NE-SE FEW ACSL/AC S-NW PK WND 2929/15/ WNDCHILL -13F/ 8/540 53000 10007 20006 10 A.M. Weather: Clear, few stratocumulus distant offshore NE-SE and few altocumulus distant west, few cirrus Temperature: 16F, Dew point: -7F, Wind: WNW at 11G19 kts, Wind; Direction variable WSW to NW Sea-level pressure: 30.21 inches Hg, rising Visibility: 80 miles BHO SA 1455 CLR 80 230/16/-7/3011G19/021/ SC LYR OFFSHR DSNT NE-SE FEW AC DSNT W FEW CI/ WND 25V31 8/541 52005 1 P.M. Weather: Clear, stratocumulus offshore distant ENE-ESE, few altocumulus and altocumulus lenticular WNW-NNW, cirrus distant WSW-W Temperature: 25F, Dew point: -5F, Wind: W at 11G20 kts, Wind: Direction variable WSW to NW Sea-level pressure: 30.14 inches Hg, falling Visibility: 80 miles 6-hour max. temp: 25F BHO SA 1755 CLR 80 208/25/-5/2811G20/014/ SC DSNT OFFSHR ENE-ESE FEW AC/ACSL WNW-NNW CI DSNT WSW-W WND 24V31/ 8/541 58022 10025 20007 WEATHER SUMMARY FOR THURSDAY, DECEMBER 17 TEMPERATURE (DEGREES F) MAX.....22 NORMAL.....38 MIN......7 NORMAL.....23 MEAN....15 NORMAL.....31 DEPARTURE FROM 30-YEAR AVERAGE............-16 TOTAL DEPARTURE FOR THE MONTH.............+17 [+0.8 DEGREES/DAY] HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY............50 DEPARTURE.......+16 TOTAL HEATING UNITS FOR THE MONTH...........524 DEPARTURE.......-13 TOTAL HEATING UNITS FOR THE SEASON.........1684 DEPARTURE......-142 TOTAL HEATING UNITS LAST SEASON TO DATE....1738 DIFFERENCE......-54 PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY.............52 WNW AT 5:43 A.M. AEROVANE..............52 WNW AT 5:42 A.M. ASOS..................48 W AT 6:15 A.M. DAVIS.................49 WNW AT 5:43 A.M. THE FASTEST MILE FOR YESTERDAY...........32 WNW AT 5:43 A.M. MAXIMUM 2-MINUTE ASOS AVERAGE............31 W AT 5:42 A.M. MAXIMUM 2-MINUTE DAVIS AVERAGE...........33 W AT 5:42 A.M. AVERAGE WIND SPEED AND DIRECTION.......20.9 WNW ASOS................18.6 DAVIS...............20.2 W W [285 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..........3.94 DEPARTURE....+1.45 ASOS..............4.01 TOTAL PRECIPITATION FOR THE YEAR..........53.51 DEPARTURE....+4.36 ASOS.............54.77 SNOWFALL (INCHES) THROUGH THIS MORNING (EST) TOTAL SNOWFALL 24 HRS ENDING 7 A.M......... 0.0 DEPARTURE.....-0.4 TOTAL SNOWFALL FOR THE MONTH...............11.0 DEPARTURE.....+5.9 TOTAL SNOWFALL FOR THE SEASON..............14.0 DEPARTURE.....+6.0 PRELIMINARY CLIMATE SUMMARY FOR DECEMBER 2009 CALENDAR DAY DATA DATA REPORTED: DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/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 12/1 41/28/35/-1/0/0/497/89 29 NW 12/2 51/33/42/+6/0.08/0/345/62 30 SSE 12/3 67/47/57/+22/1.01/0/428/77 69 SSE AERO 73 MPH SSE 12/4 52/40/46/+11/0/0/488/88 26 W 12/5 42/30/36/+1/0.79/4.7/000/00 36 N 12/6 33/25/29/-5/0.09/0.6/513/93 36 NW 12/7 36/25/31/-3/0/0/050/09 22 WSW 12/8 39/25/32/-3/0/0/512/93 27 WNW 12/9 45/29/37/+4/1.23/5.7/000/00 52 ENE AERO 46 MPH ENE 12/10 40/26/33/0/0/0/351/64 46 WSW AERO 39 MPH W 12/11 26/20/23/-9/0/0/395/72 46 WSW AERO 41 MPH WSW 12/12 30/18/24/-8/0/0/548/100 36 W AERO 33 MPH W 12/13 46/23/35/+3/0.74/0/274/50 35 SSE AERO 31 MPH SSE 12/14 41/33/37/+6/0/0/186/34 29 NW 12/15 46/34/40/+9/0/0/006/01 35 W AERO 32 MPH W 12/16 35/22/29/-2/T/T/459/84* 43 W AERO 44 MPH W 12/17 22/7/15/-16/0/0/545/100 52 WNW AERO 52 MPH WNW 12/18 our morning low temp: 6F; the normal low is now 23F * sunshine % and mins. corrected down 1%, 5 mins. NEW DAILY RECORD FOR DECEMBER 2009 12/3 NEW RECORD HIGH MAXIMUM TEMPERATURE of 67F; surpasses previous record of 61F in 1932, 1950. DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated): RECORDS FOR DECEMBER 18 HIGH 59 IN 1928 LOW -11 IN 1919 PRECIP 1.44 INS. IN 1915 SNOWFALL 7.0 INS. IN 1904 PEAK GUST 76e W IN 1978 RECORDS FOR DECEMBER 19 HIGH 59 IN 1899 LOW -1 IN 1919 PRECIP 2.06 INS. IN 1986 SNOWFALL 14.1 INS. IN 1945 PEAK GUST 68 NE IN 1986 TODAY'S REPORT PREPARED BY: Robert Skilling