About the Dashboard Graphics
This page provides full descriptions of the weather, climate, and water graphics that are displayed in the WWA Intermountain West Climate Dashboard, and provides links to additional resources related to those graphics.
The temperature and precipitation maps are derived from observations at individual meteorological stations in the National Weather Service Cooperative Observer Network (COOP), and the Automated Weather Data Network (AWDN). Interpolation (estimation) of values between these known points is performed to produce continuous shaded contours. Interpolation procedures can cause incorrect values in data-sparse regions.
Note that observations from NRCS SNOTEL sites are not included in these maps; therefore, most high mountain areas are in the “data-sparse” regions subject to interpolation errors, if the climate anomalies differ between mountain areas and the nearest COOP and AWDN stations, at lower elevations.
These maps are products of the High Plains Regional Climate Center (HPRCC), using data delivered through the Applied Climate Information System (ACIS) developed at the University of Nebraska-Lincoln. These near-real-time data should be considered to be preliminary, having been subjected to minimal quality control.
In these maps, “average” refers to a 1981–2010 climate normal.
For additional temperature and precipitation maps, and for maps of other climate variables including individual station data, visit HPRCC.
Snowpack telemetry (SNOTEL) sites are automated stations operated by the USDA Natural Resources Conservation Service (NRCS) that measure snow water equivalent (SWE), the depth of water that would result by melting the snowpack at the measurement site. SWE is determined by measuring the weight of snow resting on a pressure-sensitive pillow (like a very large bathroom scale) at the SNOTEL site, and converting that measurement into inches of water equivalent.
The Current Snowpack as % of Normal map from NRCS depicts the conditions averaged across a set of SNOTEL sites that are either within or immediately adjacent to the outlined basin. For each SNOTEL site that is actively reporting data, the current SWE is calculated as percentage of the historic (1981-2010) median SWE for that date. Then for each basin, these % of normal values for active SNOTEL sites are averaged across each basin to generate the % of normal value for that basin. The number of SNOTEL sites representing each basin ranges from 1 to 31, depending on the basin and the number of actively reporting sites. This table from NRCS has the same data as in the map, but also reports the number of SNOTEL sites reporting for each basin.
Note that SNOTEL sites are point samples of complex and spatially variable basin snowpacks. Collectively, the SNOTEL sites within a basin may over- or under-estimate actual basin snow conditions, particularly if the highest and lowest elevations in a given basin (which have fewer SNOTEL sites) have unusual snowpack anomalies. Also, not all SNOTEL sites may be reporting on a given day.
For additional SNOTEL maps visit NRCS here.
For State Basin Outlook Reports, visit NRCS here and select the state from the dropdown menu.
The US Drought Monitor maps are based on expert synthesis of drought indicators including (but not limited to) the Palmer Drought Severity Index, soil moisture, streamflow, precipitation, and measures of vegetation stress, as well as reports of drought impacts. The USDM categories are assigned so that they generally correspond with one or more of the objectively measured indicators, listed above, being in these percentile classes:
D0 (abnormal dryness) – 20th-30th percentile
D1 (moderate drought) – 10th-20th percentile
D2 (severe drought) – 5th-10th percentile
D3 (extreme drought) – 2nd-5th percentile
D4 (exceptional drought) – 0th-2nd percentile
The USDM is produced in partnership between the National Drought Mitigation Center (NDMC) at the University of Nebraska-Lincoln, the United States Department of Agriculture, and NOAA. The US Drought Monitor is released weekly (every Thursday) by the NDMC, and it represents data collected through that Tuesday. Both academic and government drought experts participate in weekly calls to discuss changes to the forthcoming USDM, and this input is compiled by the author(s) named on each week’s map.
The weekly state USDM maps for Colorado, Utah, and Wyoming show the same drought categories and boundaries as the nationwide map, but at a higher spatial resolution and with the county boundaries shown, so that local conditions can be more easily discerned.
Each USDM is released with a text discussion (scroll down) that provides supporting detail on drought conditions in different parts of the country.
The SPI is a drought index, developed by then-Colorado state climatologist Thomas McKee and others, based on the historical probabilities of receiving a given amount of precipitation over a given period. The SPI was designed to explicitly capture that it is possible to simultaneously experience relatively wet conditions on one or more time scales, and relatively dry conditions at other time scales. Consequently, a separate SPI value is calculated for different time scales.
The SPI maps shown on the Dashboard are developed by the National Drought Mitigation Center (NDMC) and the High Plains Regional Climate Center (HPRCC). The HPRCC SPI maps shown here, updated daily, are also available at timescales of 1, 2, 4, 6, 9, and 24 months. The Western Regional Climate Center (WRCC) produces a set of national SPI maps showing values for each climate division, updated monthly, at timescales of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 18, 24, 30, 36, 48, 60, and 72 months.
The historical probabilities of receiving a given amount of precipitation are standardized so that an SPI of zero indicates the mean historical precipitation (1981-2010), and other SPI values correspond to the number of standard deviations that the observed precipitation value departs from the long-term mean, for a normally distributed random variable. Since precipitation is not normally distributed at most timescales in most regions, a transformation is first applied so that the transformed precipitation values follow a normal distribution.
An SPI value of -1 indicates moderate drought severity and means that only 16% of all periods would be expected to be drier. An SPI value of -2 indicates severe drought, with only 2.5% of periods would be expected to be drier. For more information on the SPI and how it is calculated see this page at the Western Regional Climate Center.
The Evaporative Demand Drought Index (EDDI) exploits the strong physical relationship between evaporative demand (E0) and actual loss of water from the land surface through evapotranspiration. E0 is the “thirst of the atmosphere,” estimated by the amount of water that would evaporate from the soil and be transpired by plants if the soil were well watered. EDDI measures the signal of drought using information on the rapidly evolving (daily) conditions of the atmosphere to estimate their impact on land-surface moisture, and vice versa. EDDI’s effectiveness in reflecting the moisture conditions on the land surface is based on feedbacks between the atmosphere and land that are particularly strong during the warm season, when drought is of greatest concern. See this 2-page description of EDDI for more information.
The data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record..
The drought category shown (D0, D1, D2, D3, D4) is a function of the depth of reference evapotranspiration accumulated over a given period of record (4-week, 8-week, 12-week) with respect to a climatology of 1981-2010. The drought categories are consistent with the US Drought Monitor's Percentile Ranking Scheme.
These state maps from USGS show the current (actually the previous day’s) daily streamflow compared to historical streamflows for that gage for day of the year. The color of the circle indicates the percentile ranking of the current daily streamflow among the distribution of historic daily streamflows; see the key below the map thumbnail images. “Low” (red) means the current flow is the record low for that date, while “High” (black) means that the current flow is the record high for that date. The open circles indicate gages that are reporting current flows, but don’t have sufficiently long historic records to be given a percentile ranking.
To access the current flow data for each gage shown on the map, click the “Current Streamflow – XX” header above each thumbnail map, then when that page from USGS loads, mouse-over the gage of interest.
Additional streamflow maps are available from USGS here.
The streamflow forecast map shown from January through May is generated by NRCS, based on their forecasts for one or more forecast points within each basin. The map colors indicate the forecasted spring-summer runoff as a percent of the 1981-2010 normal spring-summer runoff.
(Important Note: Starting in water year 2013, NRCS and NOAA will continue to collaborate on streamflow forecasts, but the forecast values will no longer be strictly coordinated between some of the NOAA NWS River Forecast Centers, including the Colorado Basin River Forecast Center; thus, the NRCS forecast may differ from the NOAA forecast for the same forecast point in the Colorado Basin.)
Forecasts of natural runoff are based principally on observations of precipitation, snow-water equivalent (SWE), and antecedent precipitation in the fall before winter snowfall begins. The forecasts become more accurate as the season progresses and the influences on spring-summer runoff are increasingly captured in the observations. The forecasts earlier in the season assume that climatic factors during the remainder of the snow accumulation and melt season will have an average affect on runoff.
For more information about NRCS streamflow forecasts, go here.
Additional streamflow forecast information:
NOAA streamflow forecasts are available through the following websites of individual River Forecast Centers (RFCs):
- Colorado Basin RFC (also includes Great Basin)
- Missouri Basin RFC (includes South Platte and North Platte)
- West Gulf RFC (includes Rio Grande)
- Arkansas Basin RFC
NOAA/NWS River Basin Forecast Centers in the western U.S. have an interactive website that shows streamflow forecasts as inputs to reservoirs.
For NRCS State Basin Outlook Reports, visit here and select the state from the dropdown menu.
For a monthly summary of snowpack conditions and streamflow forecasts for the western U.S. from the NRCS National Water and Climate Center, visit here.
These diagrams are generated daily by Reclamation based on their latest operational data. The fraction that each tea-cup symbol is filled indicates the current reservoir contents as a fraction of the capacity (i.e., % Full). The size of the teacup is not proportional to the capacity of the reservoir. The first two values provided next to each teacup (e.g., 208746/344800) are the reservoir contents in acre-feet and the capacity in acre-feet, respectively.
Additional reservoir teacup diagrams or operational data for Colorado, Utah, and Wyoming can be accessed as follows:
Great Plains region of Reclamation (includes Bighorn Basin, Boysen, Buffalo Bill, Colorado-Big Thompson, Fry-Ark, North Platte, Wind River) - alternate page.
Upper Colorado Region of Reclamation (includes Upper Colorado River Basin, Upper Rio Grande Basin, and nearly all of Utah).
For reservoirs that are not operated by Reclamation (including Bear Lake, Dillon Reservoir, Strawberry Reservoir, and many others), see the NRCS State Basinwide Reservoir Summaries (updated monthly).
The NOAA CPC seasonal temperature outlooks forecast the likelihood (percent chance) of the 1-month or 3-month temperatures occurring in the above-average, near-average, and below-average categories, based on the historic (1981-2010) distribution of temperatures. These three categories, or terciles, are bounded so that an equal fraction (33.3%) of the historic temperatures is in each category.
The numeric values on the maps do not refer to actual temperature values, but to the probability, in percent, that temperatures will be in one of these three terciles, if that probability is different than 33.3%. The shading indicates areas in which the odds are tilted towards warmer-than-average (A, orange shading) or cooler-than-average (B, blue shading) condition. The numeric values indicate the probability that temperatures will be in the above-average or below-average tercile--with a corresponding decrease in the opposite category. The near-average category remains at 33.3% likelihood, unless the forecast probability is very high for the above- or below-average tercile, or a near-average forecast is more likely than the other two categories.
Thus, areas with dark orange shading indicate a 40.0–50.0% chance of below-average, a 33.3% chance of near-average, and a 16.7–26.6% chance of above-average temperatures. Light orange shading displays a 33.3–39.9% chance of below-average, a 33.3% chance of near-average, and a 26.7–33.3% chance of above-average temperatures, and so on. Equal Chances (EC) represents equal odds or a 33.3% probability for each tercile, indicative of areas where forecast signals are weak or conflicting. “N” indicates an increased chance of near-average conditions, but this is not forecast very often.
The skill of the temperature outlooks largely comes from the status of ENSO, and recent warming trends.
Seasonal Precipitation Outlook (NOAA Climate Prediction Center - CPC)
The NOAA CPC seasonal precipitation outlooks forecast the likelihood (percent chance) of the 1-month or 3-month temperatures occurring in the above-average, near-average, and below-average categories, based on the historic (1981-2010) distribution of precipitation. These three categories, or terciles, are bounded so that an equal fraction (33.3%) of the historic precipitation values is in each category.
The numeric values on the maps do not refer to actual precipitation values, but to the probability, in percent, that precipitation will be in the most likely of these three terciles, if that probability is different than 33.3%. The shading indicates areas in which the odds are tilted towards wetter-than-average (A, green shading) or drier-than-average (B, brown shading) condition. The numeric values indicate the probability that precipitation will be in the above-average or below-average tercile--with a corresponding decrease in the opposite category. The near-average category remains at 33.3% likelihood, unless the forecast probability is very high for the above- or below-average tercile, or a near-average forecast is more likely than the other two categories.
Thus, areas with dark brown shading indicate a 40.0–50.0% chance of below-average, a 33.3% chance of near-average, and a 16.7–26.6% chance of above-average precipitation. Light brown shading displays a 33.3–39.9% chance of below-average, a 33.3% chance of near-average, and a 26.7–33.3% chance of above-average temperatures, and so on. Equal Chances (EC) represents equal odds or a 33.3% probability for each tercile, indicative of areas where forecast signals are weak or conflicting, or the forecast is believed to have poor skill. “N” indicates an increased chance of near-average conditions, but this is not forecast very often.
The skill of the precipitation outlooks largely comes from the status of ENSO.
Quantitative Precipitation Forecasts (QPFs) are issued by the NOAA Hydrometeorologic Prediction Center (HPC) and incorporate the latest surface and upper air analyses, radar data, satellite data, and model guidance from the NAM, NGM, GFS and RUC forecast models. The 5-day QPF map shows the total precipitation expected over the 5-day period between the “Valid” and “Thru” dates shown in the lower left corner of the map. The contour intervals (left side) are in inches. Any closed contour with a forecasted value over 1” is marked with an “x”, and the forecasted value is shown on the map.
More information about the QPFs from NOAA HPC is available here.
The experimental seasonal precipitation guidance (aka “SWcast”) for CO, UT, NM, and AZ is generated on a roughly bimonthly basis by Klaus Wolter of NOAA PSD. It depicts the shift in tercile probabilities for precipitation in the 3-month season shown, similar in concept to the NOAA CPC precipitation outlooks.
In order to be indicated on this map, the forecast tilt in the odds has to be at least 3% either towards wet (above-average), dry (below-average), or near-normal (average). Shifts towards the wettest tercile (“W”) are indicated in green and are contoured in 5% increments; shifts towards the driest tercile (“D”) are indicated in red and are contoured in 5% increments; and enhanced chances of near-normal conditions of at least 3% are indicated by the letter “N”. Shifts over 10% are considered significant. Positive (negative) shifts between three and five percent are indicated by a green (red) plus (minus) sign, while minor shifts of one or two percent are left blank in this display. A question mark (“?”) indicates enhanced odds of both the wettest and driest terciles, while the middle tercile is less likely.
Presentations by K. Wolter to the Colorado Water Availability Task Force (WATF), including a discussion and executive summary of the latest PSD experimental guidance product, are archived here (click on "Long Term Weather Forecast).
“Niño 3.4” refers to the region of the equatorial central Pacific from 120°W to 170°W and 5°N to 5°S, which is widely used for monitoring ENSO conditions. The Niño 3.4 SST time-series graph, produced by the International Research Institute for Climate and Society (IRI) at Columbia University, shows monthly SST anomalies in the Niño 3.4 region from January 1982 to present. Values below zero (blue) indicate cooler temperatures, with persistent anomalies below 0.5°C being classified as La Niña (ENSO cold-phase) events. Conversely, values above zero indicate warmer temperatures, with persistent anomalies above 0.5°C being classified as El Niño (ENSO warm-phase) events. The arrow at the far right of the graph indicates the most recent monthly value.
The ENSO Prediction Plume, also produced by IRI, shows 24 different model forecasts of SST in the Niño 3.4 region for nine overlapping 3-month periods (e.g., OND = October-December) extending 11 months into the future. Differences among the forecasts of the models reflect both differences in model design, and actual uncertainty in the forecast of the possible future SST scenario. The expected skills of the models, based on historical performance, are not equal to one another. The skills also generally decrease as the lead time increases.
For more information about the ENSO forecasts, see the IRI page here.
For a technical discussion of current El Niño conditions, see the ENSO Diagnostic Discussion, a collaborative effort of the several parts of NOAA, including the research labs, the IRI, and other institutions funded by NOAA (updated on the second Thursday of the month).
For updated graphics of SST and SST anomalies, visit here and click on “Weekly SST Anomalies”:
This graphic, updated monthly, shows the most recent MEI values (black squares and line) as compared with several historical ENSO events of the same sign--La Niña or El Niño--and similar intensity (colored triangles and lines).
The Multivariate ENSO Index (MEI) was developed by Klaus Wolter and others at NOAA PSD to monitor ENSO conditions using a broader range of indicators than just SST, as in the Niño 3.4 index. MEI is based on these 6 variables, as observed over the tropical Pacific: sea-level pressure (P), zonal (U) and meridional (V) components of the surface wind, sea surface temperature (S), surface air temperature (A), and total cloudiness fraction of the sky (C). MEI is calculated monthly from the two-month running average of these variables.
MEI is similar to SST-based indices like Niño 3.4 in that negative values indicate cool-phase (~La Niña) conditions while positive values indicate warm-phase (~El Niño) conditions. Persistence of values less than -0.5 indicate La Niña events, while persistence of values greater than 0.5 indicates El Niño events. This definition of ENSO events may not always correspond to the official NOAA ENSO designations based on the Niño 3.4 index.
For more information about the MEI, see Klaus Wolter's MEI page.
The Seasonal Drought Outlook (DO) depicts general, large-scale trends from that date through the end of the forecast period (3 to 3.5 months, depending on the date of issue). The delineated areas in the DO are defined subjectively based on expert assessment of numerous indicators described above, including outputs of short- and long-term forecasting models, as well as consideration of the typical seasonal cycle (it is easier to come out of a drought during the wettest time of year, just as it is easier to worsen a drought situation during that time of year, depending on its moisture anomalies). Areas of continuing drought are approximated from the US Drought Monitor (categories D1 to D4). Note: The green areas imply at least a one-category improvement in the Drought Monitor intensity levels, but do not necessarily implythe cessation of drought conditions.
For weekly drought updates, see the latest Drought Monitor text (updated weekly).
For more drought information of all kinds, visit the US Drought Portal.