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NWS new local three-month temperature outlook
Published August 23, 2006
On the third Thursday of every month, researchers, farmers, ranchers, and a multitude of others with an interest in climate turn to the national threemonth temperature and precipitation outlook issued by NOAA’s Climate Prediction Center for a glimpse at what conditions to expect (see pages 15 and 16). Now, thanks to a new product that went online last month, they have the option of zooming in on climate prediction information at a local level.
On July 21, NOAA’s National Weather Service (NWS) introduced the Local Three-Month Temperature Outlook (L3MTO), the first in a series of online local climate products to be released by the NWS over the next two years. The L3MTO is available on all NWS Weather Forecast Office (WFO) climate webpages, offering users pie charts, tables, and text to help interpret the outlook for local climate conditions. The local climate pages can be easily accessed from a national map at http://www.weather.gov/climate/. The NWS hopes to unveil a downscaled Local 3-Month Precipitation Outlook (L3MPO) in 2008.
The L3MTO is downscaled or translated from the three-month national temperature outlook, but contains the same type of information: the likelihood (chance) of above-average, average, and below-average temperature, and the probability of exceedance—the expected chance for a certain temperature to be exceeded during a given time. The difference is that the L3MTO extracts more spatial detail, presents the product information in several different formats, and provides interpretation information.
The L3MTO is available for about 1,160 locations nationwide, although the number of locations could increase to approximately 4,000 sites in the future, depending upon user requirements. The product’s web interface includes clickable maps and text options to help navigate from one location to another. For example, Figure 1 displays all the locations around Phoenix, AZ, where the L3MTO is available. Users can move within and between states by using the arrow feature above the map.
While the national three-month outlook allows users to gain quick at-a-glance information for the entire country, it does not provide enough detail to be useful at the local level (Figure 2). The L3MTO is presented in several different formats to meet a wide range of user needs. The first product format you will encounter online is a series of pie charts. The pie chart provides the most likely category, as well as the probability for the other two categories to occur, while the national outlook only provides the most likely category.
The next product format of the L3MTO suite is the temperature range graph (Figure 3), which displays all 13 future 3-month forecast periods for an entire year. The climatological median is plotted between five different user-selected confidence intervals (or levels ofexpected chance), which include 99, 95, 90, 75, and 50 percent. Supportive text is available by clicking in the confidence interval for any one of the three-month periods, to help with interpretation. The median value means that during the present climatological reference period (1971–2000), 50 percent of the year’s temperature was greater than and 50 percent was less than the median.
The Probability of Exceedance component appears as a chart or a table, with the chart also displaying the observed three-month temperature for the previous five years, for comparison (Figure 4).
As with all long term outlooks and forecasts, limitations exist with the L3MTO. For example, the L3MTO cannot provide a high confidence outlook for an exact three-month temperature value or a departure from that value; the product is in probabilistic format. To help the user assess the skill of the L3MTO, every product component includes a link to a verification tool that was developed by CLIMAS and expanded to include local climate outlook hindcast information and requirements. The outlook hindcast information is available from December 1994 to 2003. A hindcast is a method of assessing forecast or model prediction accuracy in which forecasts or model results are compared with a known period in the past. The requirements include a selection of forecast target seasons and specific years for computation of verification statistics. New users are encouraged to visit the “Questions and Feedback” tab to offer suggestions on the L3MTO.
The next local outlook product, scheduled for release in the summer of 2007, is the Three-Month Outlook of Local El Niño/La Niña Impacts on temperature and precipitation. Eventually, additional meteorological parameters will be added.