A squall is a sudden, sharp increase in wind speed lasting minutes, as opposed to a wind gust, which lasts for only seconds. They are usually associated with active weather, such as rain showers, thunderstorms, or heavy snow. Squalls refer to the increase to the sustained winds over that time interval, as there may be higher gusts during a squall event. They usually occur in a region of strong sinking air or cooling in the mid-atmosphere. These force strong localized upward motions at the leading edge of the region of cooling, which then enhances local downward motions just in its wake.
The 1969 Atlantic hurricane season was the most active Atlantic hurricane season since the 1933 season, and was the final year of the most recent positive Atlantic multidecadal oscillation (AMO) era. The hurricane season officially began on June 1, and lasted until November 30. The season had the highest number of systems reach hurricane status – twelve – in a single season, until that record was surpassed in 2005. The season was above-average despite an El Niño, which typically suppresses activity in the Atlantic Ocean, while increasing tropical cyclone activity in the Pacific Ocean. Activity began with a series of five tropical depressions, the first of which developed on May 29. The third system in that series, Tropical Depression Seven, caused extensive flooding in Cuba and Jamaica in early June. The final in the series formed on July 25, the same day that Tropical Storm Anna developed. Neither the former nor latter caused significant impact on land. Later in the season, Tropical Depression Twenty-Nine caused severe local flooding in the Florida Panhandle and southwestern Georgia in September.
The 1972 Atlantic hurricane season was a significantly below average season, having only seven named storms, four fully tropical storms and three subtropical storms. It officially began on June 1, 1972, and lasted until November 30, 1972. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The first storm, Subtropical Storm Alpha, developed on May 23 off the Southeast United States and struck Florida, causing minor damage and two fatalities. Although several other tropical depressions developed, only Tropical Depression Five is known to have affected land.
The Groundhog Day gale was a severe winter storm that hit the northeastern United States and southeastern Canada on February 2, 1976.
The 1993 Storm of the Century was a large cyclonic storm that formed over the Gulf of Mexico on March 12, 1993. The storm was unique and notable for its intensity, massive size, and wide-reaching effects; at its height, the storm stretched from Canada to Honduras. The cyclone moved through the Gulf of Mexico and then through the eastern United States before moving on to eastern Canada. The storm eventually dissipated in the North Atlantic Ocean on March 15.
The 1957 Atlantic hurricane season featured one of the longest-travelling tropical cyclones in the Atlantic basin, Hurricane Carrie. Nevertheless, the season was generally inactive, with eight tropical storms – two of which went unnamed – and three hurricanes, two of which intensified further to attain major hurricane intensity. The season officially began on June 15 and ended on November 15, though the year's first tropical cyclone developed prior to the start of the season on June 8. The final storm dissipated on October 27, well before the official end of the season. The strongest hurricane of the year was Carrie, which reached the equivalent of a Category 4 hurricane on the Saffir–Simpson hurricane scale on two separate occasions in the open Atlantic; Carrie later caused the sinking of the German ship Pamir southwest of the Azores, resulting in 80 deaths.
The 1940 Atlantic hurricane season was a generally average period of tropical cyclogenesis in 1940. Though the season had no official bounds, most tropical cyclone activity occurred during August and September. Throughout the year, fourteen tropical cyclones formed, of which nine reached tropical storm intensity; six were hurricanes. None of the hurricanes reached major hurricane intensity. Tropical cyclones that did not approach populated areas or shipping lanes, especially if they were relatively weak and of short duration, may have remained undetected. Because technologies such as satellite monitoring were not available until the 1960s, historical data on tropical cyclones from this period are often not reliable. As a result of a reanalysis project which analyzed the season in 2012, an additional hurricane was added to HURDAT. The year's first tropical storm formed on May 19 off the northern coast of Hispaniola. At the time, this was a rare occurrence, as only four other tropical disturbances were known to have formed prior during this period; since then, reanalysis of previous seasons has concluded that there were more than four tropical cyclones in May before 1940. The season's final system was a tropical disturbance situated in the Greater Antilles, which dissipated on November 8.
The 1939 Atlantic hurricane season was the least active since 1930. The season had below normal activity, with only six tropical storms, of which two became hurricanes and one became a major hurricane, equivalent to Category 3 status or higher on the modern-day Saffir–Simpson scale. The first tropical cyclone formed on June 12, and the last dissipated on November 6. These dates are within the period of each year when most tropical cyclones form in the Atlantic basin.
The 1880 Atlantic hurricane season ran through the summer and fall of 1880. This is the period of each year when most tropical cyclones form in the Atlantic basin. In the 1880 Atlantic season there were two tropical storms, seven hurricanes, and two major hurricanes (Category 3+). However, in the absence of modern satellite and other remote-sensing technologies, only storms that affected populated land areas or encountered ships at sea were recorded, so the actual total could be higher. An undercount bias of zero to six tropical cyclones per year between 1851 and 1885 and zero to four per year between 1886 and 1910 has been estimated. Of the known 1880 cyclones, Hurricane Six was first documented in 1995 by José Fernández-Partagás and Henry Díaz. They also proposed large changes to the known tracks of several other storms for this year and 're-instated' Hurricane Ten to the database. A preliminary reanalysis by Michael Chenoweth, published in 2014, found thirteen storms, nine hurricanes, and four major hurricanes.
The extraordinary 1952 Groundhog Day Storm was the only Atlantic tropical cyclone on record in February. First observed in the western Caribbean Sea on February 2 as a non-frontal low, it moved rapidly throughout its duration and struck southwestern Florida early the next day as a gale-force storm. In the state, the winds damaged some crops and power lines, but no serious damage was reported. The system became a tropical storm after emerging over the Atlantic Ocean before quickly transitioning into an extratropical cyclone on February 4. Strong winds and waves washed a freighter ashore, but no injuries were related to the event. Subsequently, the storm brushed eastern New England, causing minor power outages, before it moved inland near Maine. There were no reported fatalities related to the storm.
The Late November 1984 Nor'easter occurred on the United States' Thanksgiving Day, November 22, 1984. A deep extratropical cyclone located just off the shore of Florida led to significant beach erosion and the grounding of the freighter Mercedes I for several months along the coastal town of Palm Beach. It formed unusually early, and its effects were seen unusually far south into Florida.
The November 2006 nor'easter was a powerful extratropical cyclone that formed offshore of the Southeastern United States on November 20, bringing heavy rains, high winds, beach erosion, and coastal flooding to the Carolinas and southern New England. In addition, the earliest snowfall ever noted in both Charleston, South Carolina and Savannah, Georgia occurred on the southwest side of this cyclone. Over 10,000 were without power during the storm. No longer a nor'easter, the extratropical cyclone accelerated rapidly across the North Atlantic while rapidly strengthening, becoming a cyclonic storm again by November 25, but this time with hurricane-force sustained winds. The intense low made a cyclonic loop west of Iceland, before being absorbed by another strengthening extratropical cyclone to the west of Great Britain, late on December 1.
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to severe gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone.
The 1939 Pacific typhoon season has no official bounds; it ran year-round in 1939, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northwestern Pacific Ocean.
The 1924 Atlantic hurricane season featured the earliest known Category 5 hurricane – a tropical cyclone with maximum sustained winds exceeding 155 mph (250 km/h). The first system, Tropical Storm One, was first detected in the northwestern Caribbean Sea on June 18. The final system, an unnumbered tropical depression, dissipated on November 24. These dates fall within the period with the most tropical cyclone activity in the Atlantic. Of the 13 tropical cyclones of the season, six existed simultaneously. The season was average with 11 tropical storms, five of which strengthened into hurricanes. Further, two of those five intensified into major hurricanes, which are Category 3 or higher on the Saffir–Simpson hurricane wind scale.
Tropical Storm Dean caused minor flooding along portions of the East Coast of the United States in September 1983. The seventh tropical cyclone and fourth named storm the 1983 Atlantic hurricane season, Dean developed from a frontal low to the northeast of the Bahamas on September 26. Initially subtropical, it gained characteristics of a tropical cyclone while tracking slowly north-northeastward. By September 27, the system was reclassified as Tropical Storm Dean. While tracking northward on September 28, Dean peaked with winds of 65 mph (100 km/h), shortly before curving west-northwestward and slowly leveling-off in intensity. Eventually, Dean made landfall in Virginia on the Delmarva Peninsula on September 29 as a weakening tropical storm. Dean rapidly weakened over land and was no longer classifiable as a tropical cyclone by early on October 1.
The Braer Storm was the most intense extratropical cyclone ever recorded over the northern Atlantic Ocean. Developing as a weak frontal wave on 8 January 1993, the system moved rapidly northeast. The combination of the absorption of a second low-pressure area to its southeast, a stronger than normal sea surface temperature differential along its path, and the presence of a strong jet stream aloft led to a rapid strengthening of the storm, with its central pressure falling to an estimated 914 hPa on 10 January. Its strength was well predicted by forecasters in the United Kingdom, and warnings were issued before the low initially developed.
The March 2014 nor'easter was an extremely powerful extratropical cyclone that affected much of U.S. Gulf Coast, the eastern United States, eastern Canada, and Greenland. It was the most powerful winter storm of the 2013–14 North American winter storm season, being an unusually large winter storm as well, with its gale-force wind field becoming four times larger than that of Hurricane Sandy's extratropical remnant. The storm affected various parts of the Midwest, most of the Eastern Seaboard, as well as eastern Canada, bringing extremely powerful winds, and blizzard-like conditions.
The January 2018 North American blizzard was a powerful cyclonic blizzard that caused severe disruption along the East Coast of the United States and Canada in early January 2018. The storm dropped up to 2 feet of snow in the Mid-Atlantic states, New England, and Atlantic Canada, while areas as far south as southern Georgia and far northern Florida had brief wintry precipitation, with 0.1 inches of snow measured officially in Tallahassee, Florida.
The March 2019 North American blizzard was a powerful Colorado Low that produced up to two feet of snow in the plains and Midwest. Rapid snowmelt following the storm caused historic flooding, and some areas received hurricane-force wind gusts. Comparable to the 1993 Storm of the Century, the storm was labeled a bomb cyclone after barometric pressure readings dropped in excess of 24 mbar (0.71 inHg) over a 24-hour period. After the storm entered Colorado from its origination in Arizona, the pressure dropped more than 30 mbar (0.89 inHg) and rapidly intensified over the western High Plains. The severe storm set new all-time record low barometric pressure readings in Colorado, Kansas and New Mexico. The storm itself killed only one person in Colorado, but flooding caused by the storm killed at least 3, one in Iowa and at least two in Nebraska and left ~140,000 without power in Texas.
