Climate of Colorado and the
Fort Collins Weather Station
Wendy Ryan
Assistant State Climatologist
What’s so Crazy about Colorado?
• High elevation (highest state in the Union
– by far)
• Mid-Latitude location (lively seasonal
changes)
• Interior Continental Location far from
atmospheric moisture sources
• Complex Mountain topography
The Result?
Generous sunshine and low
humidity, i.e. people like it here
Large Seasonal
Temperature Variations
Greeley, Colo.
Large diurnal temperature
ranges and rapid changes
Kersey, Colo.
Blanca, Colo.
Frequent but highly variable
precipitation
(for every “upslope,”
there’s a “downslope”)
Photo by Wendy Ryan
Lots of Snow
(sometimes)
National Annual Average Snowfall
For our latitude,
we are one of the
snowiest places in
the world!
Show Nationa PRISM map of
average annual precip
Show Colorado PRISM map of
average annual precip
Highly seasonal precipitation patterns with
considerable geographic diversity in “seasonality”
Water Year Average Precipitation for Selected Stations
Grand Junction
Vail
Vail Pass
Georgetown
Denver
Burlington
5.0
4.5
Precipitation (inches)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
A few storms contribute a large fraction of
the annual precipitation in many years
Fort Collins Daily Accumulated Precipitation
25
Accum Normal
WY2003
Precipitation (inches)
20
15
10
5
0
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Day
May
Jun
Jul
Aug
Sep
Large Year-to-Year
Variations in Precipitation
Joe Wright SWE 2010 vs 2011
SnoTel – Snow Telemetry
• High elevation monitoring of
precipitation and snowpack.
• Automation of Snow Courses
– Manual observations of SWE
and Snow Depth started in the
early 1900’s.
• Why?
– 75% of our water supply in the
Western U.S. comes from
mountainous areas.
– Traditional weather monitoring
is done in populated areas,
not remote mountain
locations.
– SnoTel fills this important data
gap for water supply
monitoring and forecasting.
Snow Water Equivalent (SWE)
• Snow Pillow
– “Pillow” that is filled
with an anti-freeze
solution.
– The weight of the
snow on the pillow
forces the solution into
the pressure
transducer where it is
measured.
– This gives us the
amount of water in the
snowpack.
Precipitation
• Height of the gage is
dictated by the
amount of snow the
site receives.
• Gage designed to
hold the annual
amount of
precipitation at the
site – Includes
summer precipitation!
• Alter shield to reduce
wind affect on gage
catch.
Rain Gage
Others?
• Some SnoTel stations have additional
equipment such as:
– Air Temperature
– Solar Radiation
– Wind Speed and Direction
– Soil temperature
– Soil moisture
What about Fort Collins?
Fort Collins Precipitation
Fort Collins Temperatures
How Do We Compare to Other
Locations?
Normal Monthly Precipitation
3
Fort Collins Z=5004'
Hourglass Z = 9520'
Steamboat Springs Z = 6636'
Monthly Precipitaton (in)
2.5
2
1.5
1
0.5
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Month
Aug
Sep
Oct
Nov
Dec
Monthly Mean Temperatures
80
Fort Collins Z=5004'
Hourglass Z = 9520'
70
Steamboat Springs Z = 6636'
Mean Temperature F
60
50
40
30
20
10
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Month
Aug
Sep
Oct
Nov
Dec
Daily Records
Station
Fort Collins
Hourglass
Steamboat Springs
All-time Max Temp
103
91
99
Station
Fort Collins
Hourglass
Steamboat Springs
Date
7/21/2005
7/8/1989
7/17/1909
All-time Min Temp
-41
-32
-54
Daily Maximum Precip (in)
4.63
2.79
2.71
Date
7/29/1997
3/19/2003
3/2/1929
Date
2/1/1951
2/5/1989
1/7/1913
How Do We Get These Numbers?
Continuous Monitoring:1889-2014
• We are a National Weather Service Cooperative Station (ID 05-3005-4)
• We take manual observations, for our official record, twice a day at
0700 and 1900 MST.
• We have a full automated station that runs continuously on a 10-minute
basis and is available here: ccc.atmos.colostate.edu/~autowx
Fort Collins Temperatures
80.0
Annual Mean Temperatures
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
1880
Annual Mean Temperature
Annual Maximum Temperature
Annual Minimum Temperature
1900
1920
1940
1960
Year
1980
2000
2020
What do we measure?
• Temperature-Max/Min/Dry
and Wet Bulb
• Precipitation
• Solar Radiation
• Barometric Pressure
• Evaporation
• Wind Run
• Snowfall and Snow Depth
Temperature Measurement Overview
• Temperature measured in ºF
for manual thermometers and
º K for electronic which are
then converted.
– Liquid-In-Glass (LIG)
Thermometers
• These are our OFFICIAL
temperature measurements
– Maximum/Minimum
Temperature System (MMTS)
• Backup to LIG
– HMP45C
• Electronic sensor that
measures both temperature
and humidity on a continuous
basis.
– Hygrothermograph
• Chart recording device that
measures temperature and
relative humidity.
Liquid In Glass
• Maximum Thermometer
– There is a constriction at the bulb of the thermometer that allows
the mercury to go up but not back down, therefore recording the
maximum temperature each day.
• Minimum Thermometer
– Alcohol filled tube (bore) with and index (glass “dumbell”). The
alcohol will flow around the index and read the current
temperature while the index will stay at the minimum temperature
unless it is pushed lower by the alcohol. The minimum is read
from the RIGHT HAND SIDE OF THE INDEX.
• Dry-bulb
– Current temperature reading
• Wet-bulb
– Dry-bulb with a “sock” that is wet with distilled water and
ventilated. As the air flow past the sock, the water evaporates
cooling the reading. The closer the wet bulb to dry bulb is greater
the humidity. The farther apart the dryer the air.
MMTS
• NWS has converted
many LIG sites to the
MMTS system.
– More consistent than
human observers.
• MMTS thermistor is
connected to a display
inside the station which
records the max/min
temperatures.
• The resistance recorded
by the thermistor is
inversely proportional to
the temperature.
HMP45C
• Measures temperature and humidity
– Temperature is measured with at platinum
resistance thermometer
• Uses platinum to detect the resistance change
with temperature.
• More accurate than thermocouples.
• Larger temperature ranges than thermistors.
– Humidity is measured with a capacitive
relative humidity sensor.
• Sense water by applying an AC signal between
two plates and measuring the change in
capacitance caused by the amount of water
present.
Hygrothermograph
• Measures temperature
(F) by sensing difference
in expansion of two metal
plates (bimetallic
element).
• Measures relative
humidity (%) by the
change in length of
human hair.
• These elements are
recorded with pens on a
weekly chart.
Precipitation
• Manual Gages- Most measure in 0.01”
– 8” NWS Standard Rain Gage
– 4” Plastic CoCoRaHS gage
– Plastic Wedge Gage
• Automated/Chart Recording Gages –
Resolution varies.
– Belfort Universal Weighing Bucket
• 0.01” reported on a weekly chart
– Fischer-Porter Weighing Bucket
• 0.1” reported every 15 minutes.
– Tipping Bucket
• 0.01” reported every 10 minutes.
Solar Radiation
• CMP3 Kip and Zonen
Pyranometer
– The CMP3 pyranometer consists of a
thermopile sensor, coated with a black
absorbent coating.
– The paint absorbs the radiation and
converts it to heat.
– The resultant temperature difference is
converted to a voltage by the copperconstantan thermopile.
– The thermopile has a field of view of
180 degrees and the angular
characteristics needed to fulfill the
cosine response requirements.
– Spectral Range of 300-2800 nm
– Measured in W/m2
Barometric Pressure
• Mercurial Barometer –
Measures actual Inches of Hg
to the thousandth of an inch.
– Our reading is corrected for
temperature but not sea level.
• Barometric Pressure Sensor
– Utilizes silicon capacitive
pressure sensor.
– Measured in millibars or inches
of Mercury.
Class A Evaporation Pan
– Made of $Monel metal$ – an alloy of Ni, Cu and Fe that has low
expansion/contraction, dull finish and low oxidation. (newer pans
are cheaper low Carbon stainless steel)
– Diameter of 47.5 in (120.7 cm) has a depth of 10 in (25 cm)
– Uses stilling well and hook gage to measure water level to
hundredth on an inch (also available in cm).
• Pan should always be <4.00” and never below 2.50”.
– Usually coupled with a totalizing anemometer which records miles
of wind blowing past the pan
– Some evaporation stations also measure max and min water
temperature.
Evapotranspiration
• Mimics plant ET using a
ceramic cap and fabric
covering.
• Cheaper than alternative
methods.
Wind
• Mounted on a 10 meter (33 feet)
tower.
• The rotation of the propeller
produces a AC voltage signal
which is counted over a
specified interval by the DCP
(data collection platform).
– Measured in mph or
meters/second.
• The wind vane is light weight
and direction sensed by a
potentiometer calibrated to N.
– Measured in Degrees.
Snow
• Manual
– Snowfall measured on white snowboards
to tenth of an inch with a simple ruler.
• Snowboard is cleared after it is measured
to reduce effects of compaction and
melting.
– Snow depth measured throughout the
station yard and averaged.
• Automated
– Ultrasonic snow depth sensors
• Send out an ultrasonic sound pulse which
bounces off the target and returns.
• Time of flight is calculated, speed of
sound in air is known (and corrected for
temperature) from which distance of travel
can be calculated.
• This distance is offset by the height of the
sensor which produces the depth of snow
on the ground.
Celebrating the History of the
Fort Collins Weather Station!
Climate Quiz
1. Which Colorado City receives the LEAST
annual precipitation?
a.
b.
c.
d.
Burlington, CO
Grand Junction, CO
Rocky Ford, CO
Center, CO
Climate Quiz
2. Which location receives the MOST
Annual precipitation?
a.
b.
c.
d.
Wolf Creek Pass
Loveland Pass
Buffalo Pass
Longs Peak
Climate Quiz
3. What is the WARMEST temperature ever
recorded in Colorado?
a.
b.
c.
d.
111
114
118
121
Climate Quiz
4. What is the COLDEST temperature ever
recorded in Colorado?
a.
b.
c.
d.
-81
-71
-61
-51
Climate Quiz
5. What city is WARMEST during the
WINTER (DJF) months?
a.
b.
c.
d.
Greeley
Las Animas
Canon City
Grand Junction
Climate Quiz
6. What city has the LONGEST growing
season?
a.
b.
c.
d.
Sterling
Fort Collins
Burlington
Palisade
Climate Quiz
7. Which site recorded the highest amount
of snowfall in one snow season?
a.
b.
c.
d.
Steamboat Springs
Wolf Creek Pass
Loveland Pass
Long’s Peak
Climate Quiz
8. What is the one day maximum
SNOWFALL for Fort Collins?
a.
b.
c.
d.
5.6”
19.0”
21.1”
26.8”
Climate Quiz
9. What is the Annual Average Temperature
Fort Collins?
a.
b.
c.
d.
45.8°
50.3°
55.6°
60.2°
Climate Quiz
10. What is the Annual Average
Precipitation for Fort Collins?
a.
b.
c.
d.
13.84”
15.84”
16.10”
19.84
Climate Quiz BONUS
Bonus.
How much and where is the current
statewide record for 24 hour
precipitation?
a.
b.
c.
d.
11.08” at Holly
11.85” at Ft. Carson
4.63” at Ft. Collins
9.08” at Boulder
For one more point, which year was it recorded?
For more information!
• Climate Center Website:
http://ccc.atmos.colostate.edu
• Fort Collins Weather Station:
http://ccc.atmos.colostate.edu/~autowx
• Chrisman Field Weather Station:
www.atmos.colostate.edu/wx/fcc/fccwx_current.php
• Coagmet:
http://ccc.atmos.colostate.edu/~coagmet
Answers!
1. D 6.98” Center
2. C 73” Buffalo Pass
3. B 114 Sedgwick (7/11/54) and Las Animas (7/1/33)
4. C -61 Maybell 2/1/85
5. C Canon City is warmest during the winter
6. D Growing season of 187 days in Palisade
7. B 837.5” Wolf Creek Pass
8. C 21.1” 11/20/79
9. B Ft Collins average temperature = 50.3 deg
10. C 16.10”
Bonus: B Fort Carson broke the Holly record of 11.08” set
in 1965 with 11.85” of rain recorded in 24 hours on
September 12, 2013.