2007 Monsoon Season Statistics

The 2007 Monsoon Season started on July 8th, after three consecutive days of the daily average dew point being at or above 55°F. The daily average dew point was 56.9°F on the 8th, 55.4°F on the 9th and 55.9°F on the 10th. The highest daily dew point average was a remarkable 70.8°F on both July 31st and August 1st. Around September 9th a large ridge persisted over the entire western United States, with a cut-off low off the coast of Northern California, as well as an area of high pressure near the southern California border with Mexico. With these two systems, the flow throughout the state turned to a dry southwesterly to westerly flow, resulting in the 2007 Monsoon coming to an end. The monsoon season was 64 days in length, with 56 of those being considered monsoon days. The longest streak of consecutive monsoon days, was twenty-four occurring from August 10th to September 2nd. A monsoon day is when the daily dew point average is at or above 55°F. The graph to the left shows the daily average dew points from July 8th to September 10th.

During the 2007 Monsoon Season, we recorded a total of 4.38in. of rainfall, with a peak rain rate of 4.68in/hr. occurring with the storm that moved through the area on September 1st. The largest storm total was 0.86in., which occurred on July 21st thru 22nd. The following, is the precipitation broken into months: July: 2.32in.  ;  August: 1.21in.  ;  September: 0.85in.

Throughout the monsoon season, nineteen storms affected the area, with thirteen of those producing measurable rainfall (>0.009in). Of those nineteen, eleven were consider minor, two moderate, five significant and one severe. The one severe storm that moved through the area occurred on September 1st, bringing with it extremely heavy rainfall and strong winds, with a peak wind gust of 47mph from the NE. This peak wind gust was the highest we recorded during the monsoon season. Clicking on the links (dates) below will take you to the storm statistics pages for some of the storms that occurred during the monsoon season. The graph below shows the total rainfall for the thirteen storms that brought the area measurable precipitation. (Notice: The six storms that were only trace amounts are not present on the graph.)

Radar Loop Available:
Photos Available:
  • July 21st thru 22nd
  • July 28th  
  • July 30th
  • July 31st  
  • August 16th
  • August 25th
  • August 29th
  • August 30th
  • September 1st  

    For a detailed list of storms that effected the area this monsoon season, and for all of 2007/2006 click the link below:
    http://www.weatherbus.com/storm_data.php

    During the entire season, from July 8th to September 10th, we recorded a total of 2,097,303 strokes of lightning, with a peak strike rate per minute of 618, occurring on July 27th at 3:45pm. The top lightning count day was July 21st, with 105,947 strokes recorded. Below is a list of the top five lightning count days:
    July 21st: 105,947
    July 22nd: 87,260
    July 27th: 83157
    July 31st: 82,909
    July 30th: 80,165


    2007 Monsoon Season TimeLine:
    1. July 8th
      1. The monsoon season starts after three consecutive days of the average daily dew point being at our above 55°F (July 8th: 56.9°F; July 9th: 55.4°F; July 10th: 55.9°F)
    2. July 8th to July 11th
      1. Four consecutive monsoon days.
      2. No storms affected the area during this time.
    3. July 12th to July 13th
      1. First break in the monsoon season.
      2. The daily dew point average on the 12th was 52.5°F and on the 13th it was 52.8°F.
    4. July 14th to July 15th
      1. Two consecutive monsoon days.
      2. One Storm
      3. Trace amount of rain was recorded during this period on the 14th.
    5. July 16th
      1. Second break in the monsoon season.
      2. Daily average dew point of 52.8°F.
    6. July 17th
      1. Dew point rises back to monsoon criteria.
      2. Daily average dew point of 55.5°F.
    7. July 18th
      1. Third break in the monsoon season.
      2. Daily average dew point of 54.2°F.
    8. July 19th - August 7th
      1. Twenty consecutive monsoon days.
      2. Ten Storms
      3. During this period, 2.36in. of rain was recorded.
    9. August 8th - August 9th
      1. Third break in the monsoon season.
      2. Daily average dew point of 54.7°F on the 8th and 54.0°F on the 9th.
    10. August 10th - September 2nd
      1. Twenty-four consecutive monsoon days.
      2. Seven Storms
      3. During this period, 1.95in. of rain was recorded.
    11. September 3rd - September 4th
      1. Fourth break in the monsoon season.
      2. Daily average dew point of 48.1°F on the 3rd, and 54.1°F on the 4th.
    12. September 5th - September 9th
      1. Five consecutive monsoon days
      2. One Storm
      3. During this period 0.03in. of rain was recorded.
    13. September 10th
      1. The 2007 Monsoon Season Ends


    2007 Monsoon Season Compared to the 2006 & 2005 Monsoon Season

    Year Begin Date End Date # of Monsoon Days Total Rain Total Lightning Count
    2007 July 8 September 10 56 days 4.38in. 2,097,303 strokes
    2006 June 28 September 15 71 days 5.38in. 3,055,634 strokes
    2005 July 17 September 9 47 days 2.43in. 1,964,184 strokes


    Public Information Statement, Released By The National Weather Service Forecast Office In Phoenix, About The Monsoon Season 

    PUBLIC INFORMATION STATEMENT...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
540 AM MST THU SEP 13 2007

...MONSOON 2007 ENDED SEPTEMBER 11TH...

THE OFFICIAL ONSET FOR THE MONSOON OCCURS WHEN THE AVERAGE DAILY DEW
POINT TEMPERATURE...AS OBSERVED AT PHOENIX SKY HARBOR INTERNATIONAL
AIRPORT...REACHES OR EXCEEDS 55 DEGREES FOR THREE CONSECUTIVE DAYS.
HOWEVER...THE ENDING DATE OF THE MONSOON REQUIRES MORE OF A
SUBJECTIVE DETERMINATION...AND IS GENERALLY DEDUCED BY LOOKING AT
UPPER LEVEL WIND PATTERNS. IF FORECAST MODELS CONTINUE TO DEPICT A
PERMANENT TRANSITION TO DRIER WESTERLY FLOW ACROSS THE REGION BEYOND
SEVEN DAYS...AND THE FLOW IS EXPECTED TO RESULT IN A PROGRESSIVE
DOWNWARD TREND OF AVERAGE DEW POINT TEMPERATURES BELOW 55 DEGREES
...A DATE CAN BE DETERMINED FOR THE EXODUS OF MOISTURE AND THE END
OF THE MONSOON.

SEPTEMBER 11TH WILL MARK THE END OF THE 2007 MONSOON SEASON FOR
PHOENIX. A BRIEF SUMMARY IS LISTED BELOW.


START DATE     END DATE      MONSOON DAYS*   PRECIPITATION (INCHES)

  JUL 19        SEP 11            48            0.67 (7/19-9/11)

*(MONSOON DAY...A DAY WHERE THE AVERAGE DAILY SURFACE DEW POINT
  TEMPERATURE REACHED OR EXCEEDED 55 DEGREES. AVERAGE IS 55 DAYS.)

HOW DID THIS SEASON COMPARE TO PREVIOUS YEARS? THIS YEAR TIED AS THE
EIGHTH DRIEST ON RECORD...AND WAS THE DRIEST SINCE 1993 WHEN 0.61
INCHES OF RAIN FELL. THE WETTEST PERIOD OCCURRED IN 1911 WHEN 8.58
INCHES OF RAIN FELL...THE DRIEST BEING 1932 WHEN 0.21 INCHES FELL.
THE LONG TERM AVERAGE FOR THIS PERIOD IS 2.35 INCHES. THIS
COMPARISON IS BASED ON DATA FROM JULY 1ST THROUGH SEPTEMBER 15TH FOR
PHOENIX...WITH RECORDS DATING BACK TO 1896.

DUE TO THE SOMEWHAT CHAOTIC NATURE OF THUNDERSTORMS ACROSS THE
VALLEY...RAINFALL AMOUNTS ACROSS THE METRO AREA CAN VARY GREATLY
EACH YEAR. SOME RAINFALL AMOUNTS FROM AROUND THE AREA INCLUDE...
4.01 INCHES AT APACHE JUNCTION...3.38 INCHES AT CASA GRANDE...4.13
INCHES AT CAREFREE...0.42 INCHES AT PHOENIX DEER VALLEY AIRPORT...
0.94 INCHES AT FOUNTAIN HILLS...AND 1.22 INCHES AT YOUNGTOWN.

A COMMONLY ASKED QUESTION IS WHETHER OR NOT RAINFALL DURING THE
MONSOON IS CHANGING /OR BECOMING LESS/. BASED ON THE LONG TERM TREND
FOR PHOENIX THE ANSWER IS NO. THE DATA SHOW THAT THERE IS GREAT
VARIABILITY FROM ONE YEAR TO THE NEXT...AND EVEN ONE DECADE TO THE
NEXT. THERE IS ALSO A LONG TERM OSCILLATION WHICH APPEARS IN THE
DATA SET...WITH PEAKS IN RAINFALL AMOUNTS /WET/ DURING THE
1910S...1950S AND 1980S...AND TROUGHS /DRY/ DURING THE 1930S...1970S
AND THE 2000S.

$$

MEYERS/INIGUEZ