BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS 02186 ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY SATURDAY, DECEMBER 19, 2009 ALL TIMES ARE IN EASTERN STANDARD TIME VERY COLD AND DRY AHEAD OF MAJOR SNOWSTORM TONIGHT... Cirrostratus and altostratus clouds have dominated the sky today with only a few breaks visible to the north and northeast. This morning was slightly warmer than yesterday with a low of 14, but a slight inversion was enough to create some dramatic looming effects on the mountains to our northwest. These were stretched above the horizon much higher than usual, and this was occurring at mid-day, much later in the day than we typically see these effects. Both Ponkapoag and Houghton's ponds were completely frozen this morning. The dew point dropped to the middle single digits below zero earlier today; these are the lowest dew points of the season so far. Today's observations: 7 A.M. Weather: Broken altocumulus, overcast cirrostratus, breaks in overcast N-NE, thin spots in overcast NW-NE, few stratocumulus offshore ENE-ESE, thin smoke layer along horizon NW-SSE Temperature: 15F, Dew point: -7F, Wind: NNW at 4 kts Sea-level pressure: 29.96 inches Hg, rising Visibility: 80 miles 6-hour minimum temp: 14F 24-hour precipitation: 0.00 24-hour snowfall: 0.00 Average snow depth: none BHO SA 1155 E200 BKN 220 OVC 80 145/15/-7/3304/996/ BINOVC N-NE THN SPTS IOVC NW-NE FEW SC OFFSHR ENE-ESE THN K LYR ALG HRZN NW-SSE WND LGT/ 8/578 55010 10016 20014 10 A.M. Weather: Overcast altostratus, few breaks in overcast distant N-NE, higher cirrostratus clouds visible distant NNW-NE, few stratocumulus offshore E-ESE, thin smoke layer along horizon all quadrants, looming of mountains WNW-NW, sun occasionally dimly visible Temperature: 19F, Dew point: -3F, Wind: NW at 9 kts, Sea-level pressure: 29.93 inches Hg, falling Visibility: 80 miles BHO SA 1455 E200 OVC 80 136/19/-3/3209/993/ FEW BINOVC DSNT N-NE HIR CLDS VSBL DSNT NNW-NE FEW SC OFFSHR E-ESE THN K LYR ALG HRZN ALQDS LOOMING OF MTNS WNW-NW SUN OCNL DMLY VSBL/ 8/578 55009 1 P.M. Weather: Scattered altocumulus, overcast altostratus, few lower cumulus E, thin smoke layer NNW-NE, looming of mountains WNW-NW, sun occasionally dimly visible Temperature: 25F, Dew point: 8F, Wind: N at 8 kts, Sea-level pressure: 29.82 inches Hg, falling Visibility: 80 miles 6-hour max. temp: 25F BHO SA 1755 120 SCT E150 OVC 80 099/25/8/3508/982/ FEW LWR CU E THN K LYR NNW-NE LOOMING OF MTNS WNW-NW SUN OCNL DMLY VSBL WND LGT/ 8/57/ 56037 10025 20015 WEATHER SUMMARY FOR FRIDAY, DECEMBER 18 TEMPERATURE (DEGREES F) MAX.....26 NORMAL.....38 MIN......6 NORMAL.....23 MEAN....16 NORMAL.....30 DEPARTURE FROM 30-YEAR AVERAGE............-14 TOTAL DEPARTURE FOR THE MONTH..............+3 [+0.0 DEGREES/DAY] HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY............49 DEPARTURE.......+15 TOTAL HEATING UNITS FOR THE MONTH...........573 DEPARTURE....... +2 TOTAL HEATING UNITS FOR THE SEASON.........1733 DEPARTURE......-127 TOTAL HEATING UNITS LAST SEASON TO DATE....1770 DIFFERENCE......-37 PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY.............37 W AT 4:10 A.M. * AEROVANE..............37 W AT 1:51 A.M. ASOS..................37 NW AT 1:34 A.M. DAVIS.................38 W AT 1:50 A.M. THE FASTEST MILE FOR YESTERDAY...........28 W AT 1:51 A.M. MAXIMUM 2-MINUTE ASOS AVERAGE............26 NW AT 5:53 A.M. MAXIMUM 2-MINUTE DAVIS AVERAGE...........29 WNW AT 1:14 A.M. AVERAGE WIND SPEED AND DIRECTION.......17.0 WNW ASOS................16.6 DAVIS...............17.1 WNW [290 DEG] * Last of several occurrences 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....+1.31 ASOS..............4.01 TOTAL PRECIPITATION FOR THE YEAR..........53.51 DEPARTURE....+4.22 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.....+5.5 TOTAL SNOWFALL FOR THE SEASON..............14.0 DEPARTURE.....+5.6 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 26/6/16/-14/0/0/.../.. 37 W AERO 37 MPH W 12/19 morning low temp: 14F; the normal low is now 23F 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 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 RECORDS FOR DECEMBER 20 HIGH 61 IN 1957 LOW -16 IN 1942 PRECIP 1.69 INS. IN 1936 SNOWFALL 8.3 INS. IN 1995 PEAK GUST 75 MPH S IN 2002 TODAY'S REPORT PREPARED BY: Mike Iacono