2004 WEATHER SUMMARY

Annandale Virginia - Barcroft Hills Weather Center

MOST UNUSUAL RECORDS

• HAIL - August 11th Record Size Hail of 2.5 inches by 3.0 inches.

Quarter size hail started around 1610 and was followed by about one or two minutes around (1616 to 1618) of very large hail that were as large as 3.0 inches by 2.5 inches.

      It put some dents in our car top and broke a cup off of my anemometer.

• TEMPERATURE - The lowest annual maximum temperature of 92 °F was recorded on four dates: May 23rd, June 17th, July 5th, and July 14th. 

• RAIN RATE - Maximum rain rate was 13.71 inches per hour on December 23rd at 1436 hours. (Lasting less than one minute at this rate but a new record rate on Davis Vantage Pro)  The five minute maximum precipitation amount in this storm was 0.49 inches and was the third most intense rainfall since rainfall intensity records were started in 1991.

• THUNDER - The first thunderstorm of the year occurred on April 23rd and was the latest first thunderstorm of the year since thunder records were started at this station in 1995.  May made up for the lack of thunder as thunder was recorded on 14 days.

TEMPERATURE

YEAR

• The average mean temperature for 2004 was 56.23 °F which was a little above average for the yearly mean temperature. The 24-year average is 55.95 °F.
• Highest annual maximum temperature 92 °F was recorded on May 23^rd, June 17^th, July 5^th, and July 14^th. This is the lowest maximum for the year on record. The earlier record was 94 °F in July 1982, August 1989, and July 2003.
• Lowest annual minimum temperature was 5 °F on January 10th (the lowest recorded minimum for year since 1994). January 10th was also the coldest day of the year with a daily mean temperature of 11.5 °F.
• There were 18 days that were equal to or greater than 90 °F for the maximum temperature in 2004. The annual average is 30 days.
• There were 89 days which were less than or equal to 32 °F for the minimum temperature.  Last year recorded 95 the most <= 32 °F days since 1996 which had 97 days. The average is 84 days.

MONTH

• January with a mean temperature of 28.3 °F was the coldest month of the year and was the coldest January since 1994. The month also had the greatest negative average monthly mean temperature departure of -5.7 °F for 2004. January had 17 days that the high temperature for the day didn’t climb above freezing. The previous 24-year record for January was 13 days in 1982 and for all months was December 1989 with 14 days. The maximum on the 10th was only 18 °F and the lowest maximum temperature in January since 1997.
• 82 °F on September the 13th, 22nd, and 23rd was a -6.5 °F departure for the lowest daily maximum for the month. This is the lowest monthly maximum temperature ever recorded for September in the last 24 years except for 1992 when 82 °F was also recorded. 
• May with a mean temperature of 70.9 °F was the warmest May since 1991 and had the greatest positive average monthly mean temperature departure of +6.4 °F for 2004.
• Both January and February had the greatest number of days (26 days) with the minimum temperature equal to or lower than 32 °F.         

DAY

· The coldest day of 2004 was on January 10^th with a daily mean temperature of 11.5 °F.  Only four Januarys in the last 24-years have had a daily mean temperature lower than the 11.5 °F. The warmest day in January was January 4th when the temperature was 72°F and tied for second place as the warmest temperature in January in the last 24 years at this station. The record was 74 °F set in 2002.

· The lowest daily maximum temperature for 2004 occurred on January 10^th and was 18 °F which was the lowest maximum for any day since January 18, 1997.

RANGE

·  The 40 °F temperature range on April 17th was the greatest daily temperature range for the year.

· The 1 °F temperature range on October 20th was the lowest daily temperature range for the year. This also holds the 24-year record for the lowest temperature range ever to occur in the last 24 years. It was a rare record for October as low temperature ranges generally occur during the winter months.

· September’s average temperature range was only 15.3 °F the eighth lowest in the last 24-years due to the cloudiness and humid conditions of this September; only January and October were lower. March had the greatest temperature range average for the month.

PRECIPITATION

YEAR

· The total number of days this year with measurable precipitation was 134 days the most for a year since 1996 other than last year when we set the 24 year record of 157.

· Total precipitation measured 43.16 inches, a departure of -1.20 inches.  The year was only a little below the average in precipitation but had 134 days with measurable precipitation.

MONTH

· The greatest number of days with measurable precipitation in one month was 16 days in May.

· The 24-year record for any month is 23 days set just last May.

· June had the greatest monthly total rainfall: 5.74 inches, a +2.23 inch departure.

· October had the least monthly total rainfall: 1.38 inches a –2.00 inch departure but March had the greatest negative departure.

DRIEST PERIOD

· February had 17 consecutive days with no precipitation which is a new 24 year record for February and the driest period since 2001 (October 17 - November 19) when we set the 24 year record of 34 days.

CALENDAR DAY

· The greatest calendar day rainfall for the year was 2.19 inches which occurred on November 12^th. This maximum calendar day rainfall was the 4^th greatest in the past 24-years for the month of November.

24 HOUR PERIOD

· The 2.27 inches of rain which occurred on November 12^th - 13^th was the most precipitation to fall in a 24-hour period for 2004.

HOUR

· The greatest one-hour rainfall 0.92 inches recorded on August 11^th was the most intense one hour rainfall for 2004.

FIVE-MINUTE

· The greatest five-minute rainfall was 0.49 inches which fell on December 23^rd, the most intense since June, 1998 when 0.56 inches occurred in five minutes. The rainfall intensity record for December is only 0.11 inches in five minutes recorded in both 1993 and 2003. It is truly remarkable that this rainfall intensity surpassed all records but two SUMMER rains of greater intensity! Only the rainfall intensities on June 16, 1998 with 0.56 inches in five minutes and July 23, 1992 with 0.58 inches (records since 1991) were more intense. The December 23^rd rain was also accompanied by a wind gust of 40 mph.

SNOW

YEAR

· The year’s total snowfall at this station was 6.5 inches that was a departure of -16.1 inches.

MONTH

· January had the greatest monthly snowfall total for the year with 6.3 inches.

STORM

· The largest snowstorm of the year was 5.0 inches on January 25^th – 26^th.

· The greatest calendar day snowfall was 3.6 inches observed on January 25^th.

· The greatest snowfall on the ground at any one time was 4.5 inches on January 26^th.

WIND

YEAR

· The highest wind recorded in 2004 was on August 11^th with a gust to 50 mph from the west at 1606 associated with a severe thunderstorm that also produced hail. This was the highest wind ever recorded here in August in the last 24 years. The previous August record was 41 mph last year. This was also the highest wind recorded since November 13^th of 2003.

MONTH

· The windiest month of 2004 was January with a total wind run of 2,264 miles.

· The maximum wind gust for June of 40 mph from the WNW on the 1st at 1507 was the strongest wind gust recorded for June in the last 24-years.

· The maximum wind gust for August of 50 mph from the west on the 11^th at 1606 was the strongest wind gust recorded for August in the last 24-years.

· The maximum wind gust for November of 48 mph from the WNW on the 25^th at 1329 is the second highest wind recorded in November in the last 24 years; only last year had a higher wind gust in November.

DAY

· The windiest day for 2004 was April 4^th with a 190.3 mile wind run.

BAROMETRIC PRESSURE

YEAR

· November 14th had the year's highest barometric pressure reading of 30.80 inches. This was the highest barometer recorded in November since 1996 and the second highest pressure ever recorded in November at Annandale Weather Center. It was also the highest for any month since Jan. 31, 1999.  (The November record is 30.81 inches in 1996.) 

• November 25th also had the year's lowest barometric pressure of 29.35 inches; that was the lowest recorded in November since 1999 and the fifth lowest pressure recorded in November in the last 24 years. It was the lowest for any month since December 11th, 2003 when 29.23 inches was recorded.

SKY COVER

MONTH

• September was the cloudiest September since 1989 which holds the 24-yeat record for the month of September.
• July’s average sky cover makes it normally the clearest month of the year but this month was the cloudiest July on my records.
• The clearest month was February which was only a little clearer than average but was the clearest month of 2004 as many months were much above the average in cloudiness particularly January, July, August,  and September.

SEASON RECORDS

Spring Season -

· The mean spring temperature was 58.1 °F which was the highest since 1991 and ranked second place for the warmest in the last 24 years.