BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS 02186 ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY WEDNESDAY MAY 5, 2010 ALL TIMES ARE IN EASTERN STANDARD TIME A BEAUTIFUL SUNNY, WARM AND DRY DAY A perfectly sunny, warm and dry day today has temperatures still running close to 10 degrees warmer than normal. The air is very dry with temperatures in the 70's by afternoon and dew points dropping into the 30's. Our relative humidity had dropped close to 25%. Visibility has been 70 miles with only some distant light haze. It is just an amazingly beautiful early May day. THUNDERSTORMS BROUGHT HIGH WIND GUSTS BUT LITTLE RAINFALL YESTERDAY AFTERNOON PEAK WIND GUSTS TUESDAY AFTERNOON, MAY 4TH 1. Maximum, Inc. Merlino: 62 MPH WNW 2. Aerovane wind system: 60 MPH WNW 3. Davis wind system: 55 MPH WNW @ 4:10 PM EDT (fastest 2-min. sustained wind: 37 MPH WNW @ 4:12 PM EDT) 4. Maximum, Inc. Merlin: 51 MPH 5. 420C recorder: 51 MPH WNW @ 4:11 PM EDT 6. ASOS recording system: 51 MPH WNW a 4:12 PM EDT (fastest 2-min. sustained wind: 37 MPH WSW @ 5:52 PM EDT) A fastest mile of 40 MPH WNW and then WSW was recorded during the two periods of very strong winds. At least one thunderstorm began with a brilliant nearby flash of lightning at 4:09 PM EDT and a downpour of rain with 0.06 in. in 5 mins. ending 4:16 PM. A second storm which may have included some thunder occurred during the late afternoon brought a peak wind gust to just under 50 MPH W and 0.03 inch of rain. Today's observations: 7 A.M. Weather: Clear, few cirrus and dense cirrus distant NNW-N, thin smoke layer south thru northwest Temperature: 56F, Dew point: 44F, Wind: W at 10 kts Sea-level pressure: 29.93 inches Hg, rising Visibility: 65 miles, 70 miles northwest, thin smoke layer south through northwest light distant haze 6-hour minimum temp: 50F 24-hourly precip: 0.09 inch BHO SA 1155 CLR 65 135/56/44/2610/993/ FEW CI/DENS CI DSNT NNW-N VSBY NW 70 THN K LYR DSNT S-NW LGT DSNT HZ/ 8/002 51024 MANUAL 70009 ASOS 70008 10056 20050 10 A.M. Weather: Clear, few cirrus distant N-ENE smoke layer aloft distant SW-NW, light distant haze Temperature: 67F, Dew point: 39F, Wind: W at 11 kts, Wind: Direction variable WSW-WNW Sea-level pressure: 29.94 inches Hg, rising Visibility: 70 miles, light distant haze BHO SA 1455 CLR 70 139/67/39/2711/994/ FEW CI DSNT N-ENE K LYR ALF DSNT SW-NW DSNT LGT HZ WND 24V30/ 8/001 51004 1 P.M. Weather: Clear, few small cumulus forming distant WNW-N, thin smoke layer aloft NW-E, patches haze aloft Temperature: 75F, Dew point: 38F, Wind: WNW at 13G20 kts, Wind: Direction variable WSW-NNW Sea-level pressure: 29.92 inches Hg, falling Visibility: 70 miles, light distant haze 6-hourly max. temp: 75F BHO SA 1755 CLR 70 131/75/38/2913G20/992/ FEW SML CU FRMG DSNT WNW-N THN K LYR ALF NW-E PTCHS THN HZ ALF WND 24V33/ 8/100 56008 10075 20056 WEATHER SUMMARY FOR TUESDAY, MAY 4 TEMPERATURE (DEGREES F) MAX.....81 NORMAL.....63 MIN.....52 NORMAL.....43 MEAN....67 NORMAL.....53 DEPARTURE FROM 30-YEAR AVERAGE...............+14 TOTAL DEPARTURE FOR THE MONTH................+70 [+17.3 DEGREES/DAY] HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY.............0 DEPARTURE.......-12 TOTAL HEATING UNITS FOR THE MONTH.............0 DEPARTURE.......-51 TOTAL HEATING UNITS FOR THE SEASON.........5482 DEPARTURE......-595 TOTAL HEATING UNITS LAST SEASON TO DATE....5925 DIFFERENCE.....-443 PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY.............51 WNW AT 3:11 P.M. AEROVANE..............58 WNW AT 3:11 P.M. ASOS..................51 WNW AT 3:12 P.M. DAVIS.................55 WNW AT 3:10 P.M. THE FASTEST MILE FOR YESTERDAY...........40 WSW AT 4:53 P.M. * MAXIMUM 2-MINUTE ASOS AVERAGE............37 WSW AT 4:52 P.M. MAXIMUM 2-MINUTE DAVIS AVERAGE...........37 WNW AT 3:12 P.M. AVERAGE WIND SPEED AND DIRECTION........13.5 WSW ASOS.................13.5 DAVIS................12.3 W [260 DEG] * last of several occurrences... PRECIPITATION (INCHES) THROUGH THIS MORNING (EST) TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.09 DEPARTURE......-0.04 ASOS..............0.08 TOTAL PRECIPITATION FOR THE MONTH..........0.13 DEPARTURE......-0.39 ASOS..............0.11 TOTAL PRECIPITATION FOR THE YEAR..........30.49 DEPARTURE.....+12.02 ASOS.............30.56 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......-0.1 TOTAL SNOWFALL FOR THE SEASON..............64.4 DEPARTURE......+4.3 PRELIMINARY CLIMATE SUMMARY FOR MAY 2010 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 5/1 81/58/70/+18/0.00/0.0/.../.. 29 SE 5/2 87/56/72/+20/0.00/0.0/.../.. 29 SSW 5/3 80/62/71/+18/T/0.0/.../.. 41 W AERO 50 MPH W 5/4 81/52/67+14/0.09/0/.../.. 51 WNW AERO 58 MPH WNW TSTM 5/5 our morning low temp: 50F; the normal low is now 44F NEW DAILY RECORDS FOR MAY 2010 5/1 - minimum temp. of 58F equals record high minimum for the date set in 2001 DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated): RECORDS FOR MAY 5 HIGH 92F IN 1949 LOW 30F IN 1891 PRECIP 2.74 INCHES IN 1922 SNOWFALL 3.0 INCHES IN 1917 PEAK GUST 58 MPH S IN 1966 & 58e MPH SW IN 1976 RECORDS FOR MAY 6 HIGH 90F IN 1930 LOW 29F IN 1891 PRECIP 1.04 INCHES IN 1890 SNOWFALL TRACE IN 1917,1996 PEAK GUST 65 MPH SSE IN 1989 TODAY'S REPORT PREPARED BY: Robert Skilling