Wednesday, February 18, 2015

ABC4 Dan Pope's Pinpoint Forecast - afternoon February 18th 2015

SNOWLESS IN SALT LAKE CITY!


Tuesday, February 17, 2015

Smith and Morehouse Reservoir 2013

Smith and Morehouse Reservoir Utah scenic photos - Matt Pope 2013



ABC4 Chief Meteorologist Dan Pope's Pinpoint Forecast - February 17th, 2015

Moab 2006

Moab Utah scenic photos - Matt Pope 2006






Saint George 2003

Saint George Utah scenic photos - Matt Pope 2003







Snow Canyon 2003

Snow Canyon Utah scenic photos - Matt Pope 2003









ABC4 Dan Pope's Pinpoint Forecast - Evening - February 17th, 2015

Fox 13 Morning forecast for February 17th, 2015

KUTV - Weather forecast for Tuesday evening, Februrary 17, 2015

Monday, February 16, 2015

ABC4 Chief Meteorologist Dan Pope's Pinpoint Forecast - February 16th, 2015

Short sleeve WX for Utah's Dixie! Lots of sunshine next 7 days with temps in the 70's

Will we go 5 for 5 in record breaking high temps for SLC?

Unusually warm weather for February

Friday, February 13, 2015

January Monthly Weather Almanac



January Monthly Weather Almanac
in Text and Link Format

WeatherCasts:
7-Day Forecasts by ABC4 Weather:
     http://www.abc4.tv/weather/
7-Day Forecasts by the National Weather Service:
     http://www.wrh.noaa.gov/slc/forecast/textproduct.php?pil=SFT&sid=UT
ClimateCasts:
Driest Days of January in Salt Lake City (<30% Chance of Precipitation):
     1, 6-9, 21, 25-26, 29
Wettest Days of January in Salt Lake City (>35% Chance of Precipitation):
     5, 10-11, 13, 15-16, 18, 23, 28
Long-Range Climatic Outlook (by the UCCW):      http://www.utahweather.org/UWC/utahs_climate/long_range_outlook.html
Long-Range Climatic Outlook (by the NWS-CPC):
     http://www.cpc.noaa.gov/products/predictions/long_range/two_class.html
Climatic normals and records:
     http://www.wrcc.dri.edu/summary/climsmut.html
Historical daily weather events in Utah:
     http://www.utahweather.org/UWC/utahs_daily_wx_almanac/Utahs_daily_weather_history.html
AstroCasts:
Lunar Phases:
     http://tycho.usno.navy.mil/vphase.html
For visible planets and other astronomical events:
     http://www.hansenplanetarium.net/
For Sunrise & Sunset Tables, Moon Rise & Moon Set Tables:      http://aa.usno.navy.mil/data/docs/RS_OneYear.html
Holiday Weather Information for Salt Lake City:
     
http://www.wrh.noaa.gov/Saltlake/climate/holidaywx.html

Wednesday, February 11, 2015

Wood Burning Advisories

In the fall of 1992, a Wood and Coal Burning Control Program was instituted by the Department of Environmental Quality for the State of Utah, in cooperation with the public, to control woodsmoke emissions and carbon monoxide along the Wasatch Front. The woodburning program was started because chemical analysis of particulate filters showed that 16% of the particulate on the filters came from woodsmoke. The idea is to prevent an exceedance of the particulate, or PM10 (National Standard of 150 micrograms/cubic meter), and the carbon monoxide standard (9 parts per million) during winter inversions. The program starts on November 1 and ends on March 1.
The Wood and Coal Burning Control Program uses three colors (green, yellow and red) to let the public know when they can or cannot burn wood or coal in stoves or fireplaces. Green means wood/coal burning is allowed. Yellow means a voluntarily reduction of all wood/coal burning. Red means to stop all residential burning--unless the wood/coal stove or fireplace is the only source of heat for the home. Warnings and fines may be levied against anyone ignoring a no-burn period.
Click here for more information on Utah's Wood and Coal Burning Advisories
Much of the information for this section originally appeared in the copyrighted book Utah's Weather and Climate, edited by Dan Pope and Clayton Brough, in 1996. UCCW Directors have received permission from the copyright owners of this book to reproduce such information on its website and to revise and updated it where appropriate.

Weather Terms and Definitions

ClimateThe average and expected weather conditions of an area over a long period of time--usually for 30 years or more.
Climatologist: A person who studies the climate and its effect on the environment. Climatologists analyze long-term weather patterns and make long-range weather predictions. Today, a professional climatologist usually has a degree in climatology, geography, or meteorology.
Cold front: The boundary between an advancing cold air mass and a relatively warmer air mass. Generally characterized by steady precipitation followed by showers.
Disturbance/Impulse: An unsettled area of weather located in the middle or upper part of the atmosphere. Clouds and precipitation are often present.
Fair: Less than 4/10ths opaque cloud cover, no precipitation, and no extremes in temperature, visibility or wind.
Front: The transition zone between two distinct air masses. The basic types are cold, warm, and occluded fronts. Stormy weather is often found along a front.
High: The center of a high-pressure area, which is an air mass with barometric pressure exceeding atmospheric pressure. Usually brings dry, fair weather, and is accompanied by outward wind flow.
Hydrologist: A person who studies the properties and distribution of water. Hydrologists analyze the earth's water supply and predict surface runoff. Today, a professional hydrologist usually has a degree in hydrology, engineering, or meteorology.
Inversion: Warmer air above colder air, a reversal of the normal situation.
Jet streamStrong narrow bands of winds in the atmosphere. These winds often steer fronts and low-pressure systems.
Low: The center of a low-pressure area, which is an air mass with barometric pressure less than atmospheric pressure. Usually accompanied by cyclonic and inward wind flow, and often produces cloudy, stormy weather..
Meteorologist: A person who studies the atmosphere and its weather. Meteorologist analyze atmospheric phenomena and make short and medium-range weather forecasts. Today, a professional meteorologist usually has a degree in meteorology or physics. 
Microburst: A strong local downdraft from a thunderstorm with peak gusts lasting two to five minutes.
Orographic uplift: Air forced vertically by hills and mountains. It can create clouds and rain. 
Precipitation: Any water, whether liquid or solid that falls from the atmosphere to the ground. It includes rain, snow, hail and sleet.
Precipitation Probability: The stated probability (or percent change) of precipitation is a specific forecast giving the chance for precipitation at any point in the forecast area. For example: if a 40% probability is forecast for a specific location, measurable precipitation (above a "trace") should be received at that location four times out of 10 such forecasts; or there are four chances out of 10 that it will rain at a particular point during the period of the forecast.
Words used to qualify such probability forecasts--known as "expression of uncertainty"--are as follows:
%
Expressions
Area Qualifying
0%
None
None
10-20%
Slight chance
Isolated or few
30-50%
Chance
Scattered
60-70%
Likely
Numerous
80-100%
Near certain 
Near certain
Ridge: An elongated area of high pressure in the atmosphere.
Showers: Precipitation that starts and stops suddenly, or that occurs for only a short period of time.
Trace: A precipitation amount too small to measure. Less than one hundredth of an inch of precipitation.
Trough: An elongated area of low pressure.
Virga: Streaks or wisps of precipitation falling from a cloud but evaporating before reaching the ground.
Weather: The condition of the atmosphere at any given time and place with respect to temperature, pressure, winds, humidity, cloudiness, precipitation, etc.
Williams Wave: A "wave" that forms on a cold front because of developing low pressure in Nevada. The wave moves eastward along the front, causing the front to stall and intensify. The front then produces heavy precipitation as it moves through Utah. This meteorological phenomena is called a "Williams Wave" after meteorologist Phil Williams who discovered that this type of storm can bring very heavy snow to Salt Lake City. A Williams Wave can bring four to six inches of snow in less than twelve hours to the valleys of the Wasatch Front, and one to two feet of snow within 24 hours to the higher Wasatch Mountains. Depending on the position of the jet stream and storm front, central and southern Utah can also experience Williams Waves.
Much of the information for this section originally appeared in the copyrighted book Utah's Weather and Climate, edited by Dan Pope and Clayton Brough, in 1996. UCCW Directors have received permission from the copyright owners of this book to reproduce such information on its website and to revise and updated it where appropriate.

Weather Instruments

The following weather instrument companies provide weather instruments that are suitable for individuals or schools. 

Weather Information for Gardeners

Through the different stages of development, fruit can withstand different critical temperatures. Kill rates differ to the percentage of buds that could die if temperatures
drop below the critical level. Fruit trees should normally be planted in April.
CRITICAL TEMPERATURE CHART

STAGE OF DEVELOPMENT

FRUIT
KILL RATE
1
2
3
4
5
6
7
8
9
GREEN FRUIT
APPLES

50%
9
14
19
24
26
27
27
27
27
30
APRICOTS

50%

10
16
19
22
25
26


30
PEACHES

50%
10
13
16
20
24
26
27


30
PEARS

50%
8
13
20
22
24
25
26
26

30
PRUNES

50%
7
10
14
20
24
25
26
26

30
SWEET CHERRIES
10%
17
22
25
26
27
27
28
28
28
30
TART CHERRIES
10%
5
19
26
27
27
28
28
28

30

Early Planting Schedule

Asparagus, Cabbage, Onions, Spinach and Turnips
March 15 - May 1
Peas
March 15 - May 15
Broccoli
March 15 - July 15
Radishes
March 15 - September 1
Lettuce, Parsnips, Potatoes, Cauliflower, Parsley, Swiss Chard
March 20 - July 1

Late Planting Schedule

Dry Beans
May 5 - June 11
Celery
May 5 - June 15
Sweet Corn
May 5 - July 1
Summer Squash, Cucumber, Spinach
May 5 - June 20
Peppers, Eggplant
May 20 - June 20
Lima Beans, Cantaloupe, Tomatoes, Snap Beans, Winter Squash, Watermelon, Soybeans
May 20 - June 10

PLANTING TIPS

Start semi-hardy vegetables indoors:
Peppers 8 weeks
Tomatoes 6 weeks
Squash and Melons 3-4 weeks

Plant seeds when soil is very dry.
Pick an area that gets full sun all day and has good soil.
Pick recommended varieties of vegetables.
Around 15-20 days after you have planted your lettuce, radishes, etc., replant for a staggered harvest.
Add organic matter such as sawdust, compost, leaves, or straw to your garden. This will enhance the capacity of the water retention in sandy soil, and allow oxygen to get to roots in clay soil.

Water adequately - usually 1.50" per week.
Fertilize at time of planting and once per month.
Enjoy your harvest!

Much of the information for this section originally appeared in the copyrighted book Utah's Weather and Climate, edited by Dan Pope and Clayton Brough, in 1996. UCCW Directors have received permission from the copyright owners of this book to reproduce such information on its website and to revise and updated it where appropriate.

Sunshine

Utah receives plenty of sunshine. On an annual basis, Salt Lake City receives 67% of all possible sunshine, averaging 125 clear days, 101 partly cloudy days, and 139 cloudy days a year. In comparison, Milford receives 70% of all possible sunshine, averaging 151 clear days, 103 partly cloudy days, and 111 cloudy days. Salt Lake City's sunniest month is July (with 83% possible sunshine), while Milford's brightest month is June (with 83% possible sunshine).
The average daily accumulation of solar energy generally increases the farther south one travels from the Utah-Idaho border. Average daily accumulations range from 400 langleys in the northern part of Utah, to about 500 langleys in the extreme southwestern part of the state. (A langley is a unit of radiant energy equal to one gram calorie per square centimeter.) The greatest energy accumulations occur during the summer months. Logan/USU averages about 670 langleys per day during July, and Salt Lake City about 690. South of Utah, Las Vegas, Nevada averages about 748 langleys in June. By contrast, the accumulations during the month of December are 275 langleys at Las Vegas, while in the northern portion of the state, Salt Lake City accumulates an average of only 154 langleys and Logan/USU 148 langleys.

Much of the information for this section originally appeared in the copyrighted book Utah's Weather and Climate, edited by Dan Pope and Clayton Brough, in 1996. UCCW Directors have received permission from the copyright owners of this book to reproduce such information on its website and to revise and updated it where appropriate.

Freeze Dates and Freeze-Free Season

Freeze Dates (in PDF) for numerous Utah cities and locations have been published by Dr. Donald T. Jensen, retired Utah State Climatologist of the Utah Climate Center at Utah State University, Logan, Utah. 

Air Quality and Pollution

The valleys of the Wasatch Front of northern Utah experience their greatest concentrations of nitrogen oxides, carbon monoxide and particulates from November through February. Ozone reaches its highest concentrations in June through August. Highest concentrations of nitrogen oxides and carbon monoxide occur during the morning and evening rush-hour periods of traffic. Ozone reaches its peak during early afternoon. During the spring and fall months, there are minimal short-lived episodes of pollution. During these transition seasons, sufficient circulation exists due to weather systems to preclude significant pollution episodes.
Surface visibility is reduced due to the pollution in the atmosphere. Back in the coal burning days, Salt Lake City recorded 29 days in January 1944 of haze and smoke that reduced the visibility to six miles or less. Additionally, 25 days of haze and smoke were noted in November 1937, and 26 days in November 1944. As in the case of heavy fog, November through February are the "pollution" months. An even 100 days of haze and smoke was noted in this period during the late fall and winter of 1943-1944.
Since 1948, there has been an average of 41 days of haze and smoke during November through February. December and January average 13 days, February eight days, and November seven days. 
Much of the information for this section originally appeared in the copyrighted book Utah's Weather and Climate, edited by Dan Pope and Clayton Brough, in 1996. UCCW Directors have received permission from the copyright owners of this book to reproduce such information on its website and to revise and updated it where appropriate.

February Monthly Weather Almanac


February Monthly Weather Almanac
in Text and Link Format

WeatherCasts:
7-Day Forecasts by ABC4 Weather:
     http://www.abc4.tv/weather/
7-Day Forecasts by the National Weather Service:
     http://www.wrh.noaa.gov/slc/forecast/textproduct.php?pil=SFT&sid=UT
ClimateCasts:
Driest Days of February in Salt Lake City (<30% Chance of Precipitation):
     1, 3-5, 7, 9-10, 15, 19-21, 24-29
Wettest Days of February in Salt Lake City (>35% Chance of Precipitation):
     8, 12, 14, 16-18, 22-24
Long-Range Climatic Outlook (by the UCCW):      http://www.utahweather.org/UWC/utahs_climate/long_range_outlook.html
Long-Range Climatic Outlook (by the NWS-CPC):
     http://www.cpc.noaa.gov/products/predictions/long_range/two_class.html
Climatic normals and records:
     http://www.wrcc.dri.edu/summary/climsmut.html
Historical daily weather events in Utah:
     http://www.utahweather.org/UWC/utahs_daily_wx_almanac/Utahs_daily_weather_history.html
AstroCasts:
Lunar Phases:
     http://tycho.usno.navy.mil/vphase.html
For visible planets and other astronomical events:
     http://www.hansenplanetarium.net/
For Sunrise & Sunset Tables, Moon Rise & Moon Set Tables:      http://aa.usno.navy.mil/data/docs/RS_OneYear.html

For 2000 & Beyond: Surviving Utah's Severe Weather
     video and other educational resources:
     
http://www.utahweather.org/education.html

Tuesday, February 10, 2015

March Monthly Weather Almanac

March Monthly Weather Almanac
in Text and Link Format

WeatherCasts:
7-Day Forecasts by ABC4 Weather:
     http://www.abc4.tv/weather/
7-Day Forecasts by the National Weather Service:
     http://www.wrh.noaa.gov/slc/forecast/textproduct.php?pil=SFT&sid=UT
ClimateCasts:
Driest Days of March in Salt Lake City (<25% Chance of Precipitation):
     6-10, 18, 20-21
Wettest Days of March in Salt Lake City (>40% Chance of Precipitation):
     2, 11, 13-14, 24
Long-Range Climatic Outlook (by the UCCW):      http://www.utahweather.org/UWC/utahs_climate/long_range_outlook.html
Long-Range Climatic Outlook (by the NWS-CPC):
     http://www.cpc.noaa.gov/products/predictions/long_range/two_class.html
Climatic normals and records:
     http://www.wrcc.dri.edu/summary/climsmut.html
Historical daily weather events in Utah:
     http://www.utahweather.org/UWC/utahs_daily_wx_almanac/Utahs_daily_weather_history.html
AstroCasts:
Lunar Phases:
     http://tycho.usno.navy.mil/vphase.html
For visible planets and other astronomical events:
     http://www.hansenplanetarium.net/
For Sunrise & Sunset Tables, Moon Rise & Moon Set Tables:      http://aa.usno.navy.mil/data/docs/RS_OneYear.html

River Safety Information:     http://www.kcwc.org/RiverSafety.aspx

Tornadoes

video

Winter Storms

video

Lightning

video

Flash Floods

video

Monday, February 9, 2015

Avalanches

video

Experimental Long-Range Weather Predictions

Experimental Long-Range Weather Predictions

by R. Clayton Brough, UCCW Climatologist, May, 2005
     During the past several years, an increasing number of individuals and companies have inquired about the accuracy of various long-range weather predictions offered by private companies and non-government sources. Currently, UCCW officials are analyzing some of these long-range predictions and their claims of accuracy--which will be publicized in 2006.
     For example, the The Old Farmer's Almanac claims that it uses "a secret formula that was devised...in 1792" which "predict[s] weather trends and events by comparing solar patterns and historical weather conditions with current solar activity." This Almanac claims that "although neither we nor any other forecasters have as yet gained sufficient insight into the mysteries of the universe to predict the weather with total accuracy, our results are almost always very close to our traditional claim of 80 percent [accuracy]."
     In comparison, WeatherPlanner claims that it uses a "proprietary scientific process" based on "historical weather information" that was "originally developed in the 1930s by Dr. Irving P. Krick." This company--which produces daily weather predictions "of expected precipitation and temperatures up to a year in advance" for specific locations--claims that some of its predictions "were correct 77 percent of the time in 1998 and 83 percent of the time in 1999."
     Although I do not endorse or support the methods or predictions made by the The Old Farmer's Almanac, WeatherPlanner, or other such companies or sources, I do feel that these predictions are "interesting" or "possibly useful" if and when they match known climatological precipitation probabilities--such as days or weeks which are statistically (and historically) the wettest during a particular month for a specific location.

 

Comparative Study of Long-Range Forecasts from two Commercial Providers and Forecasts using Climatology
and Persistence to Actual Observations taken at
Salt Lake City, Utah, over a Twelve-Month Period (2004-2005)

by Dan A. Risch, Meteorologist, CCM
Associate Chairman, Board of Consultants, UCCW
August, 2006
     This study compares weather parameters at Salt Lake City, Utah that were forecast by two long-range commercial forecast providers to actual observed conditions. The parameters of temperature and precipitation where used in the study and a determination was made as to how well the two providers did in forecasting a year in advance for Salt Lake City, Utah. These two providers are referred to as Provider A and Provider B. The time period this study covers is slightly different for each provider. Provider A covers November 2004 through October 2005. Provider B covers December 2004 through November 2005. So there is a one month shift in the study periods. Additionally climatology and persistence forecasts were compared to the actual Salt Lake City conditions. The time period used for the climatology and persistence forecasts were December 2004 through November 2005.
     The results of the temperature forecast comparison show that Provider A was correct 39 percent of the time while Provider B was correct 47 percent of the time. Climatology was correct 55 percent of the time, and Persistence was correct 65 percent of the time.
     Results for the combined yes- / no-precipitation day forecasts, showed Provider A was correct 54 percent of the time, Provider B was correct 59 percent of the time, climatology was correct 60 percent of the time, and persistence was correct 70 percent of the time. The forecasts for yes-precipitation days only, show Provider A was correct 46 percent of the time, Provider B was correct only 19 percent of the time, climatology was correct 30 percent of the time, and the persistence forecast was correct 57 percent of the time.
     In general there was little skill shown by Provider A or Provider B. Their highest scores were a little above 50/50 with the correct forecasts in the combined yes- and no-precipitation day forecast. It is interesting to note that if no precipitation had been forecast for the entire year that the resultant correct forecasts would have been near 60%. The Climatology and Persistance forecasts both outperformed the two commercial Providers.
DATA COLLECTED FROM PROVIDERS
Provider AForecast information covering the period from November 2004 through October 2005 was collected from this provider. This provider issued forecasts using blocks of days to which they applied word descriptors indicating what type of temperatures and precipitation they were forecasting.
For temperature forecasts Provider A used the following terms: 



  • chilly
  • cool
  • cooler (coming off of hot)
  • cold
  • very cold
  • hot
  • mild
  • milder (coming off of cold)
  • seasonable
  • warm

  • For precipitation forecasts Provider A used the following terms:




  • rain
  • rain showers
  • snow
  • snow showers
  • showers
  • snowstorm
  • thunderstorms

  • Provider B

    Forecast information covering December 2004 through November 30, 2005 was collected from this provider. Forecast data for December 1 and 2 were not available. This provider issued forecasts on a daily basis through the period of interest. These forecasts used temperature ranges for the daily maximum's, and descriptors indicating what type of precipitation they were forecasting.

    For temperature forecasts Provider B used:




  • a range for maximum temperature

  • For precipitation forecasts Provider B used the following terms:




  • rain
  • chance of rain
  • rain likely
  • snow or snow showers
  • chance of snow or snow showers
  • rain/snow at higher elevations
  • chance of rain/snow at higher elevations
  • thunderstorms/showers
  • chance of thunderstorms/showers

  • DATA COLLECTED FROM SALT LAKE CITY
    All though there are several locations in the Salt Lake Valley that collect temperature and precipitation data. The official site representing Salt Lake City is located at the Salt Lake City International Airport (KSLC) and is operated by the National Oceanic and Atmospheric Administration (NOAA) through the National Weather Service (NWS). It is this site that was chosen to provide the actual weather data for comparison to the forecast data from the two providers and to climatology. The NWS provides a summary of daily weather conditions recorded at the airport site. This summary includes maximum and minimum temperatures and precipitation in both snow and liquid forms. The summary is published monthly in a form called WS Form F-6 which is available on the Salt Lake City NWS web site. It is from this form that the comparative data for KSLC was collected for the period of November 2004 through November 2005.

    COMPARING THE DATA
    Temperature

    With Provider A, a scheme was developed to convert the terms used to describe the temperature conditions so that they could be directly compared to the actual temperatures recorded. A simple above normal, normal and below normal table was developed. Provider A temperature terms were then put into this three category table using the following criteria:
    chilly = below normal
    cool = below normal
    cooler (coming off of hot) = above normal
    cold = below normal
    very cold = below normal
    hot = above normal
    mild = normal
    milder (coming off of cold) = below normal
    seasonable = normal
    warm = normal

    Provider B gave temperature ranges with their forecasts and these could be directly compared to actual records with no conversion necessary.

    The actual temperature records from KSLC were converted to fit in the 3 category table developed for Provider A's temperature forecasts to allow for comparison to those forecasts. Inserting the actual recorded maximum and minimum temperatures into one of the three categories as described for Provider A was done by looking at the standard deviation of the normal maximums and minimums for each day for KSLC. If either the daily maximum or daily minimum temperature (or both) were above one standard deviation higher than the average maximum or minimum for the day, then that day was added to the above normal category. Similarly, if either the maximum or minimum temperature (or both) were below one standard deviation lower than the average maximum or minimum for the day, then that day was added to the below normal category. All other days were added into the normal category.

    The standard deviations used in this exercise were taken from the Western Regional Climate Center (WRCC) web site (http://www.wrcc.dri.edu/climsum.html). These deviations were based on KSLC data over the 30 year period from 1971 through 2000. The standard deviations were calculated separately for each days maximum and minimum temperature.

    A "climatology" forecast for temperatures was also developed. Average temperatures for the period from 1971 through 2000 were used as the climatological forecast. Additionally a "persistence" forecast was developed, where the maximum and minimum temperatures that occurred on one day were used as the forecast for the next day.
    Precipitation

    In the case of both Provider's, if a forecast of precipitation of either rain or snow was given for any particular day, then that day was considered a forecast precipitation-day. Forecasts using the term "chance" or the term "high elevation" as used by Provider B were considered a non-precipitation-day forecast. This day was then compared directly to the KSLC precipitation records. If a trace or more of either rain or snow or both fell on a particular day that was a forecast precipitation-day by a Provider it was considered to have been correct (a hit). Additionally if no precipitation was forecast and no precipitation occurred then it was also considered a hit.

    As with temperature forecasts, a "climatology" forecast for precipitation was developed. The method used for this forecast could be considered a modified climatology. In this method the average number of days that experience precipitation each month of the year was tabulated. This information was taken from NOAA Technical Memorandum NWS WR-152, Climate of Salt Lake City, Table 36. Table 36 is based on data from 1928 through 2001. The percentage chance for precipitation for each day of the year was then assessed. This data was also collected from NOAA Technical Memorandum NWS WR-152, Climate of Salt Lake City, Table 42a. Table 42a is based on data from 1928 through 2001.

    Each month was looked at individually. The average number of days that precipitation fell for a particular month was used as the number of forecast precipitation days for that month. This number was then used to find which actual days in the month to use for the precipitation-day by comparing the days with the highest chances of precipitation for that particular month, and using the number of highest-percent-chance days corresponding to the number of average days of rain the month had. For example, in January, Salt Lake City averages 10 days in the month with precipitation. So the 10 days in January that had the highest percentage chance for precipitation were chosen to be the days that precipitation fell in the climatology forecast.

    The persistence forecast was developed by forecasting precipitation for the day after a day which recorded precipitation and forecasting no precipitation for the day following a day which recorded no precipitation.

    RESULTS SUMMARY

    Temperature

    Provider A, using word descriptor forecasts for temperature that were tabled in an above normal, normal, below normal scheme was then compared to actual temperatures from KSLC, which were processed into the same above normal, normal, and below normal scheme by using plus or minus one standard deviation from the average maximum and minimum temperatures. This produced results showing Provider A temperature forecasts were correct 36 percent of the time.

    Provider B, using maximum temperature range forecasts for the daily maximum compared to the actual maximum temperature was correct 47 percent of the time with their temperature forecasts.

    Climatology, using average maximum and minimum daily temperatures, which by default are all "normal" temperatures, and comparing them to the above normal, normal, below normal scheme developed for Provider A was correct 55 percent of the time.

    Persistence, comparing maximum and minimum forecast temperatures that were tabled in the temperature scheme described above for Provider A and compared to the actual maximum and minimum temperatures that were also tabled in the same temperature scheme, was correct 65 percent of the time.

    Precipitation
    Provider A, using descriptor forecasts for type of precipitation compared to a yes/no on actual precipitation was correct 46 percent of the time on a forecast of 162 precipitation days and correct 54 percent of the time on a forecast of precipitation or a forecast of no precipitation (198 days). The number of actual precipitation days was 131*. For missed forecasts there were 102 cases where precipitation was predicted but none occurred and there were 65 cases where no precipitation was predicted and precipitation did occur.

    Provider B, using descriptor forecasts for type of precipitation compared to a yes/no on actual precipitation was correct 19 percent of the time on a forecast of 67 precipitation days and correct 59 percent of the time on a forecast of precipitation or a forecast of no precipitation (220 days). The number of actual precipitation days was 138*. For missed forecasts there were 39 cases where precipitation was predicted but none occurred and there were 109 cases where no precipitation was predicted and precipitation did occur.

    Climatology, using a yes/no precipitation-day compared to a yes/no actual precipitation-day was correct 30 percent of the time on a forecast of 91 precipitation days and correct 60 percent of the time on a forecast of precipitation or a forecast of no precipitation (219 days). The number of actual precipitation days was 138. For missed forecasts there were 50 cases where precipitation was predicted but none occurred and there were 96 cases where no precipitation was predicted and precipitation did occur.

    Persistence, using a yes/no precipitation-day compared to a yes/no actual precipitation-day was correct 57 percent of the time on a forecast of 137 precipitation days and correct 70 percent of the time on a forecast of precipitation or a forecast of no precipitation (256 days). The number of actual precipitation days was 138. For missed forecasts there were 54 cases where precipitation was predicted but none occurred and there were 54 cases where no precipitation was predicted and precipitation did occur.

    * the number of actual precipitation days varies between the providers due to a one month shift in the period when each provider was compared to Salt Lake City.