{"id":1555,"date":"2025-01-10T08:00:00","date_gmt":"2025-01-10T13:00:00","guid":{"rendered":"https:\/\/site.extension.uga.edu\/forsyth\/?p=1555"},"modified":"2025-01-09T10:23:11","modified_gmt":"2025-01-09T15:23:11","slug":"understanding-weather-forecasts","status":"publish","type":"post","link":"https:\/\/site.extension.uga.edu\/forsyth\/understanding-weather-forecasts\/","title":{"rendered":"Understanding weather forecasts"},"content":{"rendered":"\n
\"A
The National Oceanic and Atmospheric Administration\u2019s Temperature Outlook map shows the probability that temperatures in particular regions will be higher or lower than normal on specific dates. Image from NOAA<\/figcaption><\/figure>\n\n\n\n

Heather N. Kolich, ANR Agent, UGA Extension Forsyth County<\/p>\n\n\n\n

University of Georgia Climatologist and Director of the UGA Weather Network Pam Knox recently reported in her weekly blog, Climate and Agriculture in the Southeast, that she received numerous questions related to media reports of colder temperatures predicted to arrive in the Southeast. Some reports included \u201cominous pictures of snowfall maps showing up to a foot of snow.\u201d<\/p>\n\n\n\n

\u201cJust because someone shows a scary snowfall map on social media it does not mean it will happen or even that it is likely to occur,\u201d Knox cautioned. \u201cIt might be one out of 50 or so model runs.\u201d<\/p>\n\n\n\n

The various weather model maps are a snapshot of possible conditions at one point in time. A few hours later, the same model might show a very different map.<\/p>\n\n\n\n

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To understand weather prediction maps, let\u2019s look at the January 7-11, 2025 Temperature Outlook map from the National Oceanic and Atmospheric Agency (NOAA) (above), which was issued on January 1, 2025. The map shows a large area of dark blue covering the Southeast, which might make you think we\u2019re in for a deep freeze. What the map attempts to show, however, is the likelihood that temperatures in the regions will be higher or lower than normal for these dates. The dark blue color means that NOAA is very confident (90-100% certain) that from January 7 to January 11, temperatures will be lower than normal across the states indicated. The red color means that NOAA is confident (60-70% certain) that temperatures will be higher than normal along the west coast for those same dates. The map does not predict what the actual temperature will be, nor does it indicate how much they will vary from the normal temperatures.<\/p>\n\n\n\n

The high confidence comes from the fact that all the weather models agreed that a pattern shift would start on New Year\u2019s Eve, bringing in air from the Arctic. Weather models are complex mathematical calculations using data from several sources, such as satellite data, aircraft observations, weather balloons, stream gauges, and citizen scientists with personal weather stations. The output of the calculations helps develop weather forecasts or maps for the earth surface as well as conditions at different heights above it. There are many different models used to generate regional, global, short-range, and medium-range forecasts for temperature, precipitation, wind, and weather hazards, such as snow, freezing rain, and fire. Confidence in a forecast increases when multiple models and model runs generate very similar predictions.<\/p>\n\n\n\n

Other types of weather outlook maps show predicted anomalies across regions, such as a temporary temperature change of -15 F. This prediction indicates the temperature might be 15 degrees cooler than the normal temperature for the region at the specified time or date. In the Atlanta area in January, the normal high temperature is 54 degrees and the normal low is 36 degrees. With a -15 F anomaly, the area would temporarily experience a high of 39 degrees and a low of 21 degrees.<\/p>\n\n\n\n

\"A
A temperature anomaly forecast of -15 F predicts that temperatures in an area will be 15 degrees Fahrenheit cooler than normal temperatures for that date. Since the normal low temperature in January in Atlanta is around 36 degrees, a -15 F anomaly could mean overnight temperatures only reach 21 degrees. Image from the National Weather Service<\/figcaption><\/figure>\n\n\n\n

For the record, the January 7 early morning temperature was 23 degrees Fahrenheit according to my personal weather station. The National Weather Service predicts overnight low temperatures will remain in the 20s through Monday, January 13. That\u2019s as far out as the January 7 forecast goes. These temperatures are low enough to cause frozen water pipes, frostbite, hypothermia, or other cold injury to people, pets and livestock working or spending time outdoors.<\/p>\n\n\n\n

But what about that deep snow?<\/p>\n\n\n\n

\u201cAs far as wintry precipitation goes, most of the maps shown on social media are just clickbait,\u201d Knox cautioned. \u201cYou cannot trust any snowfall map that is more than two days out, because the conditions for snow to occur require very specific weather conditions that include cold air to hit a spot at the same time that there is enough moisture there to form wintry precipitation.\u201d<\/p>\n\n\n\n

The reason we don\u2019t see snow very often in the Southeast is that the specific snowfall conditions rarely occur. It\u2019s more usual for the moist air to move east before the really cold air arrives from the northwest. We\u2019re more likely to see freezing rain with this weekend\u2019s weather.<\/p>\n\n\n\n

But I\u2019m writing this on January 7, and I checked that forecast a few minutes ago.<\/p>\n\n\n\n

\"A
The Probability of Freezing Rain map issued by the National Weather Service on January 7, 2025 indicates that is a 5-20% chance that western parts of Georgia will experience up to .01 inch of freezing rain accumulation on Friday, January 10. Image from NWS.<\/figcaption><\/figure>\n\n\n\n

\u201cBoth the strength and timing of the temperature anomalies are going to change over time as new observations and forecast model results come in, so you need to keep monitoring forecasts for updated conditions\u201d Knox said.<\/p>\n\n\n\n

\"A
Despite social media posts claiming deep snow for Georgia first weekend of the New Year, data from numerous sources analyzed by multiple weather models correctly predicted zero snow accumulation in Georgia. Image from NWS<\/figcaption><\/figure>\n\n\n\n

Knox recommends monitoring weather forecasts through credible, scientific sources such as the NWS, which continuously monitors conditions, updates predictions, and provides unbiased information.<\/p>\n","protected":false},"excerpt":{"rendered":"

University of Georgia Climatologist and Director of the UGA Weather Network Pam Knox recently reported in her weekly blog, Climate and Agriculture in the Southeast, that she received numerous questions related to media reports of colder temperatures predicted to arrive in the Southeast. Some reports included \u201cominous pictures of snowfall maps showing up to a foot of snow.\u201d<\/p>\n

\u201cJust because someone shows a scary snowfall map on social media it does not mean it will happen or even that it is likely to occur,\u201d Knox cautioned. \u201cIt might be one out of 50 or so model runs.\u201d<\/p>\n

The various weather model maps are a snapshot of possible conditions at one point in time. A few hours later, the same model might show a very different map.<\/p>\n","protected":false},"author":452,"featured_media":1550,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[363,362],"class_list":["post-1555","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-anr","tag-weather-forecasting","tag-weather-forecasts"],"_links":{"self":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts\/1555","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/users\/452"}],"replies":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/comments?post=1555"}],"version-history":[{"count":3,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts\/1555\/revisions"}],"predecessor-version":[{"id":1558,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/posts\/1555\/revisions\/1558"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/media\/1550"}],"wp:attachment":[{"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/media?parent=1555"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/categories?post=1555"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/site.extension.uga.edu\/forsyth\/wp-json\/wp\/v2\/tags?post=1555"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}