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8-14 Day outlooks are issued daily between 3pm & 4pm Eastern Time. All forecasts issued on weekends are completely automated while all weekday outlooks are modified by the forecaster.
 
Please refer to the U.S. Prognostic Discussion for an explanation of terms and symbols used on these maps.
 
 
HOME> Outlook Maps> 8-14 Day Outlooks > About 8-14 Day maps
 
How to read the 8-14 Day Outlook Maps

Analog Maps
 

Upper Air Map

Product Interpretation: The upper air map shows the 500 hPa heights (black lines, meters) and anomalies (red for positive, blue for negative, meters) which result from averaging together the observed maps having the 10 highest pattern correlations with the official forecast. These 10 analogs are selected by performing a pattern correlation of the official forecast with observed maps in a 35-day time window centered on the centered date of the forecast, over the Pacific-North America region (60W westward to 175E, 20N to 70N), for observed maps from 1950 to 2010, and ranking the maps by their correlation scores. The 10-analog average map is then correlated with the original forecast over the PNA region, and the value of the correlation is listed in the upper left corner of the map. The 500 hPa anomalies represent the deviation of the forecast from the 1981-2010 average of 30 observed 500 hPa height maps for the same calendar period covered by the forecast. For 6-10-(8-14-)day forecasts, the averaging period of the forecast covers the centered date listed at the bottom of the image and the 2(3) days before and after the centered date, for a total for 5(7) days.

Surface Maps

Product Interpretation: These maps show the number of times, out of the top ten 500 hPa height analogs, that the observed temperature or precipitation was in either the below or the above category. These counts are indicated by the shading of the pixels on the maps, where blue or brown and red or green indicate one of 5 categories (counts ranging from 5 to 10) of the below or above category of temperature or precipitation, respectively. In white areas, the counts for either of the extreme (below or above) categories were less than 5. The categories vary by region and calendar week, and are determined by dividing the observed weekly means into three categories, each of which occurs 1/3 of the time during the climatology period (currently 1981-2010). Under ideal conditions, the coldest (driest) 10 years would define the below category, the warmest (wettest) ten years would define the above category, and the remaining years would define the middle category.

Text Data

Product Interpretation: The link on the top of the page to the top 10 analog dates in text format lists the top analogs found between 1950 and 2010 which correspond to todays official 500-HPA outlook. The analog dates selected are those with the highest correlation with the official 500-HPA outlook over the PNA region. The format of the text file is YYMMDD/PPPP where YYMMDD is the two digit year, month, and day of the analog center date and PPPP represents the number of days comprising the analog period [0500 = 5 days and 0700 = 7 days]. The order of the top 10 analogs listed are in terms of correlation value with the date corresponding to the highest correlation listed on top.




814 Day Forecasts