Climatological Report (Monthly)
Issued by NWS Denver/Boulder, CO

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CLMDEN

DENCLMDEN 000
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CLIMATE REPORT
NATIONAL WEATHER SERVICE BOULDER, CO
240 AM MDT TUE OCT 1 2013

...................................

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2013...

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2013

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH              97   09/06/2013
                        09/05/2013
                        09/04/1995
 LOW               17   09/29/1985
HIGHEST            97R  09/06        97       0       95  09/01
                        09/05
LOWEST             38   09/28        17      21       45  09/28
                                                          09/22
AVG. MAXIMUM     78.6              78.5     0.1     80.3
AVG. MINIMUM     54.2              48.3     5.9     52.3
MEAN             66.4              63.4     3.0     66.3
DAYS MAX >= 90      7               3.4     3.6        7
DAYS MAX <= 32      0               0.0     0.0        0
DAYS MIN <= 32      0               0.8    -0.8        0
DAYS MIN <= 0       0               0.0     0.0        0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         4.67   1961
 MINIMUM            T   1892
                        1944
TOTALS           5.61R             0.96    4.65     2.95
DAILY AVG.       0.19              0.03    0.16     0.10
DAYS >= .01        10               6.5     3.5        5
DAYS >= .10        10               3.3     6.7        3
DAYS >= .50         3               0.6     2.4        3
DAYS >= 1.00        2               0.1     1.9        1
GREATEST
 24 HR. TOTAL    2.39   09/14 TO 09/15           09/25 TO 09/26
                                                          09/07 TO 09/07
                                                          09/07 TO 09/07
 STORM TOTAL       MM                                 MM
 (MM/DD(HH))            MM                    09/26(00) TO 09/26(00)
                                                 09/07(00) TO 09/07(00)7
                                                 09/07(00) TO 09/07(00)7

SNOWFALL (INCHES)
RECORDS
 TOTAL             MM   MM
TOTALS            0.0               1.3

DEGREE_DAYS
HEATING TOTAL      83               125     -42       69
 SINCE 7/1         83               141     -58       69
COOLING TOTAL     133                76      57      113
 SINCE 1/1        999               764     235     1235

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
........................................................

WIND (MPH)
AVERAGE WIND SPEED              9.2
RESULTANT WIND SPEED/DIRECTION   2/183
HIGHEST WIND SPEED/DIRECTION    45/220    DATE  09/22
HIGHEST GUST SPEED/DIRECTION    64/220    DATE  09/22

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM
AVERAGE SKY COVER           0.50
NUMBER OF DAYS FAIR            8
NUMBER OF DAYS PC             14
NUMBER OF DAYS CLOUDY          8

AVERAGE RH (PERCENT)     59

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              0     MIXED PRECIP               0
HEAVY RAIN                5     RAIN                       8
LIGHT RAIN               15     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                      12     FOG W/VIS <= 1/4 MILE      4
HAZE                      1

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.

...SEPTEMBER 2013 A MONTH OF HEAVY RAINFALL AND FLOODING...

SEPTEMBER 2013 GOT OFF TO A HOT AND DRY START AS A STRONG AND
PERSISTENT UPPER LEVEL RIDGE OF HIGH PRESSURE REMAINED CENTERED OVER
COLORADO. DENVER EXPERIENCED A SEVEN DAY STRETCH OF 90+ DEGREE
WEATHER FROM THE 2ND THROUGH THE 8TH...WITH THREE DAILY HIGH
TEMPERATURE RECORDS TIED OR BROKEN DURING THIS PERIOD. THIS HOT AND
DRY PERIOD WOULD FINALLY END BY THE 9TH AS THE UPPER RIDGE SHIFTED
INTO THE CENTRAL PLAINS STATES...AND A COLD FRONT MOVED INTO
NORTHEASTERN COLORADO. THIS FRONT TRIGGERED STRONG THUNDERSTORMS
WITH VERY HEAVY RAIN AND HAIL ACROSS THE INTERSTATE 76 CORRIDOR OF
THE DENVER METRO AREA. BY THE 1OTH...THE UPPER HIGH WAS CENTERED
OVER THE SOUTHERN MISSISSIPPI VALLEY...WITH AN UPPER LEVEL LOW
PRESSURE SYSTEM CENTERED OVER SOUTHERN NEVADA. THIS PATTERN PRODUCED
A DEEP SOUTHERLY FLOW OVER THE REGION WHICH PUMPED COPIOUS AMOUNTS
OF MONSOONAL MOISTURE INTO COLORADO FROM THE SOUTH. IN ADDITION...A
WEAK STATIONARY FRONT STRETCHED ALONG THE FRONT RANGE FOOTHILLS INTO
THE PALMER DIVIDE. THIS RESULTED IN VERY COOL TEMPERATURES AND
MODERATE TO HEAVY RAIN ACROSS METRO DENVER...PALMER DIVIDE AND
FRONT RANGE FOOTHILLS. ON THE 11TH...THE STATIONARY FRONT REMAINED
OVER THE AREA WITH DEEP SUBTROPICAL MOISTURE CONTINUING FLOW INTO
COLORADO FROM THE SOUTH. BY LATE AFTERNOON OF THE 11TH...A WEAK
UPPER LEVEL DISTURBANCE MOVED INTO THE DENVER METRO AREA AND STALLED
NEAR ERIE. HEAVY RAIN BANDS ASSOCIATED WITH THIS DISTURBANCE
PRODUCED VERY HEAVY RAIN AND FLASH FLOODING ACROSS THE FOOTHILLS
FROM NORTHERN JEFFERSON COUNTY TO THE WYOMING BORDER EASTWARD INTO
THE ADJACENT PLAINS. LARIMER...BOULDER AND SOUTHWESTERN WELD
COUNTIES AS WELL AS PARTS OF AURORA WERE HARDEST HIT WITH 5 TO 9
INCHES OF RAINFALL RECORDED FROM LATE AFTERNOON ON THE 11TH THROUGH
THE MORNING OF THE 12TH. ON THE 12TH...VERY COOL TEMPERATURES ALONG
WITH AREAS OF HEAVY RAIN CONTINUED WITH AN ADDITIONAL 2 TO 6 INCHES
OF RAIN ACROSS THE FOOTHILLS AND EASTERN SECTIONS OF DENVER.
FLOODING BECAME MORE SEVERE AND WIDESPREAD DURING THE EVENING OF THE
12TH AS THE RAIN CONTINUED....WITH MANY ROADS CLOSED. RAIN DECREASED
ON THE 13TH...HOWEVER THE FLOOD WATERS SPREAD INTO THE PLAINS OF
LARIMER AND WELD COUNTIES. MORE HEAVY RAIN DEVELOPED ACROSS METRO
DENVER ON THE 14TH...WITH UP TO THREE INCHES OF RAIN MEASURED IN
PARTS OF AURORA...WITH SOME FLOODING REPORTED. ON THE 15TH...A WEAK
COLD FRONT MOVED INTO THE REGION BRINGING VERY COOL TEMPERATURES AND
MORE HEAVY RAIN TO THE AREA. ONE TO THREE INCHES OF RAIN WAS
MEASURED IN MANY AREAS...WITH FLOODING REPORTED FROM THE NORTHERN
SUBURBS OF DENVER NORTH INTO BROOMFIELD AND SOUTHWESTERN WELD
COUNTY. TOTAL RAINFALL FROM THIS EVENT RANGED FROM UNDER THREE
INCHES NEAR DOWNTOWN DENVER TO OVER 17 INCHES AROUND BOULDER AND
PARTS OF AURORA. WARMER AND DRIER WEATHER RETURNED TO THE THE FRONT
RANGE OF COLORADO ON THE 16TH AND CONTINUED THROUGH THE 21ST...AS A
DRIER SOUTHWESTERLY FLOW ALOFT DEVELOPED OVER THE REGION. UPPER
LEVEL STORM SYSTEMS BROUGHT ADDITIONAL RAINFALL TO DENVER ON THE
22ND...23RD AND THE 27TH...WITH THE COLD FRONT ON THE 27TH BRINGING
FALL LIKE TEMPERATURES TO NORTH CENTRAL AND NORTHEASTERN COLORADO.
MILD AND DRY WEATHER RETURNED TO DENVER THE LAST FEW DAYS OF THE
MONTH AS UPPER LEVEL HIGH PRESSURE BUILT OVER THE ROCKY MOUNTAIN
REGION.



TEMPERATURES:

THE AVERAGE TEMPERATURE FOR THE MONTH OF SEPTEMBER WAS 78.6 DEGREES
F WHICH WAS 0.1 DEGREES ABOVE NORMAL. SEPTEMBER OF 1948 WAS THE
WARMEST SEPTEMBER ON RECORD WITH AN AVERAGE TEMPERATURE OF 68.3
DEGREES F. THE COLDEST SEPTEMBER ON RECORD WAS 54.8 DEGREES F WAY
BACK IN 1912.

THERE WERE 7 DAYS IN WHICH THE MAXIMUM TEMPERATURE EXCEEDED 90
DEGREES...AND NO DAYS IN WHICH THE DAYTIME HIGH TEMPERATURE DID NOT
EXCEED 32 DEGREES F. THE HIGHEST TEMPERATURE OF THE MONTH WAS 97
DEGREES WHICH OCCURRED ON THE 5TH AND 6TH...AND THE COLDEST
TEMPERATURE OF THE MONTH WAS 38 DEGREES ON THE MORNING OF THE 28TH.

BELOW IS A LIST OF RECORDS FOR SEPTEMBER 2013:

DAILY TEMPERATURE RECORDS:

  DATE      TEMPERATURE   TYPE OF RECORD    OLD RECORD   YEAR LAST
SET

SEPTEMBER 5TH  97 DEGREES   TIED RECORD HIGH   97 DEGREES      1899
SEPTEMBER 5TH  97 DEGREES        RECORD HIGH   95 DEGREES      1959
SEPTEMBER 7TH  95 DEGREES   TIED RECORD HIGH   95 DEGREES      1933

PRECIPITATION:

PRECIPITATION FOR THE MONTH OF SEPTEMBER WAS 5.61 INCHES...WHICH IS
4.65 INCHES ABOVE THE NORMAL 0F 0.96 INCHES. THIS IS THE MOST
PRECIPITATION EVER RECORDED IN DENVER FOR THE MONTH OF SEPTEMBER.
TWO DAYS DURING THE MONTH REPORTED OVER ONE INCH OF PRECIPITATION
WITH 1.11 INCHES AND 2.01 INCHES MEASURED ON THE 12TH AND 14TH
RESPECTIVELY.  NEW DAILY RAINFALL RECORDS WERE ESTABLISHED ON THE
12TH...14TH AND 23RD.

DAILY PRECIPITATION RECORDS:

 DATE          PRECIPITATION    OLD RECORD   YEAR LAST SET

SEPTEMBER 12TH   1.11              0.95          2012
SEPTEMBER 14TH   2.01              0.61          1912
SEPTEMBER 23RD   0.64       0.52          2000

TOP FIVE WETTEST SEPTEMBERS

PRECIPITATION   YEAR

5.61 INCHES     2013
4.67 INCHES     1961
3.70 INCHES     1902
3.42 INCHES     1938
2.95 INCHES     2012

SNOW:

NO SNOW WAS RECORDED DURING THE MONTH. THIS IS THE 13TH CONSECUTIVE
YEAR WITH NO SNOW IN DENVER IN THE MONTH OF SEPTEMBER. THE LAST TIME
THERE WERE THIS MANY CONSECUTIVE YEARS WITH NO SEPTEMBER WAS BACK IN
THE EARLY 1900`S (1914-1926).

NINE THUNDERSTORMS WERE OBSERVED AT DENVER INTERNATIONAL AIRPORT DURING
THE MONTH. THERE WERE FOUR DAYS WITH DENSE FOG WITH A VISIBILITY AT
OR BELOW 1/4 MILE DURING THE MONTH. A PEAK WIND OF 64 MPH FROM A
SOUTHWESTERLY DIRECTION WAS RECORDED ON THE 22ND.
$$



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