backdoor cold front

File:A Satellite View of a Back-door Cold Front (14295309881).jpg

A backdoor cold front, or backdoor front, is a cold front moving south or southwest along the northeast of the Atlantic seaboard in North America, particularly in the New England region of United States and the Great Lakes. Typically occurring in spring, the front drives cool Atlantic air from the east or northeast into northeastern US that supersedes the warmer continental air. The front is termed "backdoor" because it arrives from the east, meaning it originates from the opposite direction of a typical cold front and therefore comes through the region's "back door."[https://www.theweatherprediction.com/habyhints/273/ WHAT IS A BACK DOOR COLD FRONT?] {{Webarchive|url=https://web.archive.org/web/20210417183402/http://www.theweatherprediction.com/habyhints/273/ |date=2021-04-17 }} Jeff Habby from The Weather Prediction.comEbsart, L.F., Pagnotti, V. and Lettau, B. 19 . Climatological aspects of Eastern United States back-door cold frontal passages.Mon. Weath Rev., 101, 627–35,

Formation

A backdoor cold front occurs when the clockwise motion around a high-pressure system pulls in colder air toward the south and west of it. This is where a synoptic wind motion creates a wind flow from the cool North Atlantic Ocean that brings in the backdoor front. A cold front, however, approaches from the north, northwest or west, and its wind direction will generally be from those directions (since most weather moves west to east), except this does not happen with a backdoor cold front. Rather, a back door cold front arrives from a particular direction, where it will move in an opposite direction, unlike a regular cold front.[https://www.koaa.com/weather-science/2019/02/18/what-is-a-backdoor-cold-front/ What is a Backdoor Cold Front?] {{Webarchive|url=https://web.archive.org/web/20190219033809/https://koaa.com/weather-science/2019/02/18/what-is-a-backdoor-cold-front/ |date=2019-02-19 }} KOAA News5. February 18, 2019.[https://www.mcall.com/news/weather/mc-nws-lehigh-valley-backdoor-cold-front-20190501-h6fyljkba5hfvhd55qjrvo7bcq-story.html The backdoor cold front is here. It means spring today and summer tomorrow, with storms and heavy rain ahead.] by Stephanie Sigafoos from The Morning Call. 1 May 2019.

In spring, the Atlantic ocean is still cool (below 50 F/10 C), and hence the air above it is also cool. On occasion, that air can move south out of high pressure area in the Canadian Maritimes and southward down the New England coast or the northern states. The high pressure system's clockwise flow directs cold moist air southward and westward into Northeast US. The area where these two airmasses collide is illustrated by the frontal boundary in Northern New England (near the Gulf of Maine) and northern New Jersey. Low clouds develop along and behind the front. As a backdoor cold front withdraws, temperatures can rise rapidly.[https://glossary.ametsoc.org/wiki/Backdoor_cold_front backdoor cold front] {{Webarchive|url=https://web.archive.org/web/20220306215048/https://glossary.ametsoc.org/wiki/Backdoor_cold_front |date=2022-03-06 }} American Meteorological Society. 26 January 2012

Characteristics

File:Backdoor.gif

Backdoor fronts would point toward the southeast direction, but they can alter, such as an east–west emplacement or may move towards the northeast if the cold front is encircling a subtropical cyclone. The leading boundary of this cold air forms a cold front, which is typically represented on surface analysis charts as a front aligned roughly east-west. The backdoor cold front may move towards the southwest or west. Heatwaves are frequently ended by a backdoor front – This is when temperatures are around {{convert|80|F|0}}, which is warm for May standards, whereby the front will lower the temperature down to around {{convert|50|F|0}} by the next day.[https://theweatherprediction.com/habyhints2/661/ BACK DOOR COLD FRONT] {{Webarchive|url=https://web.archive.org/web/20200113085659/http://theweatherprediction.com/habyhints2/661/ |date=2020-01-13 }} Jeffy Habby from The Weather Prediction.com

During the spring months, when ocean temperatures of the Atlantic Ocean are still cool, backdoor fronts can drop temperatures by more than {{convert|20|F-change|0}} in just a few hours, because their force is assisted by the cool, oceanic air mass that lies over the cool north Atlantic waters. They are mostly shallow, with much of the maritime air only reaching a few thousand feet aboveground and thus would rarely pass the over the Appalachian Mountains. The clouds associated with the backdoor cold front stretch from southern Illinois to North Carolina. Low clouds develop along and behind the front because such the front's winds usually come from the ocean, in addition to scattered showers, although the precipitation is mist and drizzle. Its effects may last a few hours or a couple of days, depending on the system.[https://www.weatherbug.com/news/Gloomy-Weather-It-Might-Be-A-Back-Door-Cold-Front Gloomy Weather? It Might Be A Back Door Cold Front] {{Webarchive|url=https://web.archive.org/web/20220413184105/https://www.weatherbug.com/news/Gloomy-Weather-It-Might-Be-A-Back-Door-Cold-Front |date=2022-04-13 }} By WeatherBug Meteorologist, Andrew Rosenthal. August 13, 2015.

Areas affected

Back door cold fronts are common from southeast Canada to New Jersey, due to cool Atlantic water lingering near the coast in spring. They normally impact southeastern Canada (including Nova Scotia), the New England coast, south to the New Jersey coast. New York City feels the effects of backdoor cold fronts much less than Boston. The warm Gulf Stream prevents the cool onshore flow of the front, so regions from southeast Virginia southward are typically not impacted by backdoor cold fronts. Backdoor fronts can create contrasting temperatures between the seaboard and inland areas in spring and early summer – For instance, Boston may experience cloudy skies with temperatures hovering between {{convert|40|and|50|°F|0}}, while Trenton, New Jersey, which is around {{convert|250|km|order=flip|abbr=on}} to the southwest, might experience mild and sunny conditions with temperatures near {{convert|75|°F|0}}.

=Notable examples=

On May 27, 2014, a backdoor cold front from southeast Canada came down the New England coast. Boston struggled to reach {{convert|50|°F|0}}, when it was {{convert|79|°F|0}} two days earlier. Worcester set a record low-maximum on the May 28 when it had a high of {{convert|47|°F|0}}, which was below the average high of {{convert|69|°F|0}}. In New York City, after reaching a high of {{convert|86|°F|0}} on May 27, the high only reached {{convert|64|°F|0}} the next day after the front passed. Between May 28 and 29, maximum temperatures dropped from {{convert|83|°F|0}} to {{convert|59|°F|0}} at Harrisburg, Pennsylvania and from {{convert|88|°F|0}} down to {{convert|62|°F|0}} in Washington, DC.[https://weatherworksinc.com/news/what-is-a-backdoor-cold-front Backdoor Cold Front: 40's in Late May?] {{Webarchive|url=https://web.archive.org/web/20201128193906/https://weatherworksinc.com/news/what-is-a-backdoor-cold-front |date=2020-11-28 }} Mike Murphy from Weather Works. August 6, 2014.

On March 29, 2025, after a warm front had moved northeast past New York city earlier in the day, the same front moved back southwest as a backdoor cold front later in the afternoon. Notable temperature drops were from {{convert|66|°F|0}} to {{convert|54|°F|0}} degrees in five minutes at Laguardia Airport, {{convert|79|°F|0}} to {{convert|68|°F|0}} in ten minutes at Hofstra University, and {{convert|79|°F|0}} to {{convert|53|°F|0}} in one hour at Central Park. [https://twitter.com/jackinthebachs/status/1906106611040473117] {{Webarchive|url=https://twitter.com/jackinthebachs/status/1906106611040473117 |date=2025-03-30 }}