BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS 02186
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA
 
DAILY DISCUSSION AND CLIMATE SUMMARY
TUESDAY, JULY 10, 2007   
ALL TIMES ARE IN EASTERN STANDARD TIME
 
"BACK-DOORED" TWICE IN 24 HOURS! 
TEMPERATURE DROPPED 16 DEGREES IN AN HOUR
QUASI-STATIONARY FRONT SEPERATES COOL AND 
DAMP FROM HOT AND HUMID AIRMASSES
 
Both Sunday and Monday afternoons featured the passage of 
typical "back-door" cold fronts (come from northeast)
with temperature drops of 15 to 17 degrees in just one hour. 
Yesterday the thermometer readings went from 86 degrees at 
4 p.m. to 70 degrees at 5 p.m. and then on down to 61 degrees
just a few hours later.  On Sunday, the drop went from 90 
degrees at 3 p.m. to the mid-60's in the late afternoon and 
then on down to 62 degrees during the evening.
 
An oscillating front moving back and forth across southern
New England's coastal areas during the past two days has
begun to move back northward as a warm front today
and will likely dissipate by late today.
 
We've updated the number of thunderstorm days this month to 
a total of 4 days and this has now been officialy entered into
our daily records.  Rainfall for the month has finally reached
about one inch and is close to normal for July to date. 
 
Today's observations:
 
7 A.M.   
Weather: Partial obscurement with fog obscuring 9/10 of sky    
Temperature: 66F, Dew point: 66F, Wind: SE at 04 kts 
Sea-level pressure: 29.99 inches Hg, rising
Visibility: 1/16 mile in heavy fog, variable zero in heavy fog    
6-hour min temp: 62F     
24-hour rainfall: 0.07 inch 
BHO SA 1155 –X 1/16VF 154/66/66/1304/999/ F9 VSBY 0V1/16 SUN VSB/
53012 ASOS 70006 MANUAL 70007 10066 20062 
 
10 A.M.   
Weather: Partial obscurement with haze obscuring 3/10 of sky, 
Scattered cirrus   
Temperature: 72F, Dew point: 65F, Wind: NE at 07 kts 
Sea-level pressure: 30.00 inches Hg, rising 
Visibility: 4 miles in haze
BHO SA 1455 –X 250 SCT 4H 159/72/65/0507/000/ H3/ 8/001 52005 
 
1 P.M.   
Weather: Partial obscurement with haze obscuring 1/10 of sky and
thin scattered high cirrus, few altocumulus overhead   
Temperature: 79F, Dew point: 68F, Wind: NE at 08 kts 
Sea-level pressure: 29.98 inches Hg, falling 
Visibility: 6 miles in haze, 8 miles to the southwest  
BHO SA 1755 –X 300 –SCT 6H 151/79/68/0408/998/ H1 FEW AC FLOCCUS OVHD  
8/081 58008 10080 20066 
 
WEATHER SUMMARY FOR MONDAY, JULY 9
 
TEMPERATURE (DEGREES F)
MAX.....86    NORMAL.....81 
MIN.....61    NORMAL.....61
MEAN....74    NORMAL.....71
DEPARTURE FROM 30-YEAR NORMAL........+3
TOTAL DEPARTURE FOR THE MONTH.......-15  (-1.9 DEGREES/DAY)
 
PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY..............27 NNE AT 3:24 P.M.*     
                   AEROVANE...............24 NNE AT 3:24 P.M.*   
                   ASOS...................N/A  #
                   DAVIS..................27 ESE AT 9:56 A.M.         
FASTEST MILE FOR YESTERDAY................20 NNE AT 25 NW AT 3:57 P.M.      
MAXIMUM 2-MINUTE ASOS AVERAGE.............N/A  # 
MAXIMUM 2-MINUTE DAVIS AVERAGE............22 ESE AT 9:57 A.M.          
AVERAGE WIND SPEED AND DIRECTION........ 9.0 E 
                   ASOS...................N/A  #
                   DAVIS................ 8.9 ENE [070 deg] 
* last of several occurrences...

# ASOS WINDS SWITCHED OFF BY NWS 6/6, IT IS NOT KNOWN WHEN 
THAT DATA WILL RESUME
 
PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.07  DEPARTURE.....-0.05
                         ASOS..............0.06  
TOTAL PRECIPITATION FOR JULY...............0.98  DEPARTURE.....-0.12 
                         ASOS..............0.90    
TOTAL PRECIPITATION FOR THE YEAR..........27.96  DEPARTURE.....+1.19 
                   ASOS FOR YEAR..........27.31    
 
PRELIMINARY CLIMATE SUMMARY FOR JULY 2007......CALENDAR DAY DATA
DATA REPORTED:
DATE: MAX/MIN/MEAN/DEP/PRECIP/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST
 
AERO: Aerovane recording wind system when significant
TSTM: Thunderstorm day
....: Data not yet available
 
7/1  70/52/61/-9/0.02/649/71/28 W      
7/2  73/50/62/-8/0/841/92/   29 WNW 
7/3  75/53/64/-6/0/839/92/   23 NW 
7/4  78/58/68/-2/0.09/465/51/45 SSE 
7/5  80/61/71/ 0/0.24/383/42/38 SSE TSTM *
7/6  83/62/73/+2/0.01/.../../46 WNW TSTM *
7/7  81/60/71/0/0/.../../    32 WSW  
7/8  90/62/76/+5/0.41/.../../36 NW Aero 33 MPH TSTM 
7/9  86/61/74/+3/0.20/354/39 27 NNE TSTM
      
7/10 morning low temp 62 deg; normal low 62. 
 
* TSTM days added to record, not previously recorded for this month 
  here in the daily climat reports
 
NEW DAILY RECORDS FOR JULY 2007: 
 
None to date
 
DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):
 
RECORDS FOR JULY 10
HIGH 99F IN 1911
LOW 46F IN 1890
PRECIP 1.68 INS IN 1933
WIND 75 MPH W IN 1985
 
RECORDS FOR JULY 11
HIGH 98F IN 1911
LOW 49F IN 1890
PRECIP 1.87 INS IN 1959
WIND 53 MPH NW IN 1988
 
TODAY'S REPORT PREPARED By: Robert Skilling