BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS 02186 ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY TUESDAY, DECEMBER 29, 2009 ALL TIMES ARE IN EASTERN STANDARD TIME BLAST OF ARCTIC AIR BRINGS STEADILY FALLING TEMPERATURES WEST WINDS GUSTING 50 TO 64 MPH SENDING WIND CHILL TEMPERATURES TO 5 TO 10 BELOW ZERO Wind gusts from the west early this afternoon are in the following range over 50 MPH: Maximum, Inc. Merlin 64 mph Maximum, Inc. Maestro 61 MPH W Davis system: 57 MPH W 420C system: 55 MPH W Aerovane and ASOS: 53 MPH W An Arctic cold frontal passage after sunrise this morning has been marked by some cloudiness but more importantly by strong winds together with some steadily falling temperatures from 27F at midnight to 22F at 7 a.m. Then, despite increasing amounts of sunshine, the temperature readings were dropping about one degree per hour reaching down to 15F at noon. The fastest 2-minute wind was 37 MPH W with a gust to 55 MPH W both happened at 12:25 P.M. Average wind chills have dropped to -5 to -10F. Today's observations: 7 A.M. Weather: Scattered altocumulus and altocumulus lenticularis Temperature: 22F, Dew point: 8F, Wind: W at 19G31 kts, Wind: Peak wind gust 41 kts W at 5:59 a.m. Sea-level pressure: 29.55 inches Hg, slightly Visibility: 35 miles, light haze 6-hour minimum temp: 22F 24-hour precipitation: 0.08 inch 24-hour snowfall: 0.1 inch Average snow depth: None (few small patches around summit) BHO SA 1155 70 SCT 100 SCT 35 007/22/8/2619G31/955/ FEW SC SW-NW ACSL ALQDS PK WND 2641/1059/ 8/540 ASOS 70009 MANUAL 70008 10027 20022 10 A.M. Weather: Scattered dense cirrus, broken cirrus, few stratocumulus, few altocumulus lenticularis, sun dimly visible Temperature: 18F, Dew point: 5F, Wind: W at 24G41 kts, Wind: Peak wind gust 41 kts W at 9:50 a.m. Wind: Direction variable WSW to WNW Sea-level pressure: 29.66 inches Hg, rising Visibility: 30 miles, light haze BHO SA 1455 200 SCT E220 BKN 250 BKN 30 045/18/5/2824G41/966/ FEW SC FEW ACSL DENS CI SUN DMLY VSB LGT HZ PK WND 2741/50/ WND 24V30 8/542 53038 1 P.M. Weather: Clear, few stratocumulus distant NW and along and offshore northeast thru east Temperature: 15F, Dew point: -2F, Wind: W at 30G45 kts, Wind: Peak wind W at 48 kts @ 12:25 p.m., Wind: Direction variable WSW to NW, Wind: Wind chill -4F Sea-level pressure: 29.71 inches Hg, rising Visibility: 35 miles with light distant haze 6-hour maximum temp: 22F BHO SA 1755 CLR 35 062/15/-2/2830G45/971/ FEW SC DSNT NW FEW SC ALG/OFFSHR NE-E FEW ACSL LGT DSNT HZ N-NNE PK WND 2748/25/ WND 24V31/ WNDCHILL -4F/ 8/540 51017 10022 20015 WEATHER SUMMARY FOR MONDAY, DECEMBER 28 TEMPERATURE (DEGREES F) MAX.....41 NORMAL.....36 MIN.....27 NORMAL.....20 MEAN....34 NORMAL.....28 DEPARTURE FROM 30-YEAR AVERAGE.............+6 TOTAL DEPARTURE FOR THE MONTH.............-14 [-0.7 DEGREES/DAY] HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY............31 DEPARTURE........-6 TOTAL HEATING UNITS FOR THE MONTH...........950 DEPARTURE.......+21 TOTAL HEATING UNITS FOR THE SEASON.........2110 DEPARTURE......-108 TOTAL HEATING UNITS LAST SEASON TO DATE....2126 DIFFERENCE......-16 PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY.............40 W AT 6:58 P.M. AEROVANE..............42 W AT 6:58 P.M. ASOS..................39 W AT 6:58 P.M. DAVIS.................41 W AT 6:28 P.M. THE FASTEST MILE FOR YESTERDAY...........29 W AT 6:29 P.M. MAXIMUM 2-MINUTE ASOS AVERAGE............29 WSW AT 6:30 P.M. MAXIMUM 2-MINUTE DAVIS AVERAGE...........29 WSW AT 6:29 P.M. AVERAGE WIND SPEED AND DIRECTION.......14.8 WSW ASOS................14.1 DAVIS...............13.6 SW [230 DEG] PRECIPITATION (INCHES) THROUGH THIS MORNING (EST) TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.08 DEPARTURE....-0.07 ASOS..............0.09 TOTAL PRECIPITATION FOR THE MONTH..........5.55 DEPARTURE....+1.44 ASOS..............5.74 TOTAL PRECIPITATION FOR THE YEAR..........55.12 DEPARTURE....+4.35 ASOS.............56.41 SNOWFALL (INCHES) THROUGH THIS MORNING (EST) TOTAL SNOWFALL 24 HRS ENDING 7 A.M..........0.1 DEPARTURE.....-0.3 TOTAL SNOWFALL FOR THE MONTH...............25.1 DEPARTURE....+15.6 TOTAL SNOWFALL FOR THE SEASON..............28.1 DEPARTURE....+15.7 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/-14/0/0/540/99 37 W AERO 37 MPH W 12/19 30/14/22/-8/0.01/0.1/000/00 38 N 12/20 26/16/21/-9/1.04/13.7/000/00 42 NNW 12/21 30/15/23/-7/0/0/409/75 45 WNW AERO 45 MPH WNW 12/22 28/14/21/-8/0/0/528/97 35 W 12/23 23/10/17/-12/0/0/441/81 29 W 12/24 36/14/25/-4/0/0/055/10 31 NW 12/25 35/25/30/+1/0.02/0.1/185/34 18 NNE 12/26 42/30/36/+8/0.01/0.1/000/00 38 E 12/27 52/35/44/+16/0.45/0/033/06 * 50 ESE AERO 51 MPH SE 12/28 41/27/34/+6/0.08/0.1/.../.. 40 W AERO 42 MPH W 12/29 our morning low temp: 22F thur 7 a.m.; the normal low is now 20F * sunshine added for 27th, was reported as zero NEW DAILY RECORD FOR DECEMBER 2009 12/3 NEW RECORD HIGH MAXIMUM TEMPERATURE of 67F; surpasses previous record of 61F in 1932, 1950. 12/20 NEW RECORD DAILY SNOWFALL 13.7 INCHES; surpasses previous record of 8.3 inches in 1995 DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated): RECORDS FOR DECEMBER 29 HIGH 72 IN 1984 LOW -19 IN 1933 (RECORD FOR DECEMBER) PRECIP 1.91 INS. IN 1945 SNOWFALL 18.4 INS. IN 1945 PEAK GUST 95 MPH S IN 1966 (RECORD FOR DECEMBER) RECORDS FOR DECEMBER 30 HIGH 60 IN 1984 LOW -18 IN 1933 PRECIP 1.48 INS. IN 1891 SNOWFALL 7.5 INS. IN 1956 PEAK GUST 81 MPH WNW IN 1962 TODAY'S REPORT PREPARED BY: Robert Skilling