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A monsoon is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscillation of the Intertropical Convergence Zone (ITCZ) between its limits to the north and south of the equator. Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is also sometimes used to describe locally heavy but short-term rains.
An Anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere as viewed from above. Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure.
A supercell is a thunderstorm characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather, while high-pressure areas are associated with lighter winds and clear skies. Winds circle anti-clockwise around lows in the northern hemisphere, and clockwise in the southern hemisphere, due to opposing Coriolis forces. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere (aloft). The formation process of a low-pressure area is known as cyclogenesis. In meteorology, atmospheric divergence aloft occurs in two kinds of places:
A dry line is a line across a continent that separates moist air and dry air. One of the most prominent examples of such a separation occurs in central North America, especially Texas, Oklahoma, and Kansas, where the moist air from the Gulf of Mexico meets dry air from the desert south-western states. The dry line is an important factor in severe weather frequency in the Great Plains of North America. It typically lies north-south across the High Plains states in the warm sector of an extratropical cyclone and stretches into the Canadian Prairies during the spring and early summer. The dry line is also important for severe convective storms in other regions of the world, such as northern India and Southern Africa. In general, thunderstorms and other forms of severe weather occur on the moist side of the dryline.
The 1974 Atlantic hurricane season was a near average hurricane season in terms of overall activity, with eleven named storms, of which four became hurricanes. Two of those four became major hurricanes, which are Category 3 or higher systems on the Saffir–Simpson scale. The season officially began on June 1 and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic Ocean.
The 1983 Pacific hurricane season was the longest season ever recorded at that time. It was a very active Pacific hurricane season. The season started on May 15, 1983 in the eastern Pacific, and on June 1, 1983 in the central Pacific, and lasted until November 30, 1983. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean. During the 1983 season, there were 21 named storms, which was slightly less than the previous season. Furthermore, twelve of those storms became hurricanes. And eight of the storms reached major hurricane status, or Category 3 or higher on the Saffir–Simpson hurricane wind scale (SSHWS). The decaying 1982–83 El Niño event likely contributed to this level of activity. That same El Niño influenced a very quiet Atlantic hurricane season.
The 1974 Pacific hurricane season featured one of the most active periods of tropical cyclones on record with five storms existing simultaneously. The season officially started May 15 in the eastern Pacific, and June 1 in the central Pacific, and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeast Pacific Ocean.
The central dense overcast, or CDO, of a tropical cyclone or strong subtropical cyclone is the large central area of thunderstorms surrounding its circulation center, caused by the formation of its eyewall. It can be round, angular, oval, or irregular in shape. This feature shows up in tropical cyclones of tropical storm or hurricane strength. How far the center is embedded within the CDO, and the temperature difference between the cloud tops within the CDO and the cyclone's eye, can help determine a tropical cyclone's intensity with the Dvorak technique. Locating the center within the CDO can be a problem with strong tropical storms and minimal hurricanes as its location can be obscured by the CDO's high cloud canopy. This center location problem can be resolved through the use of microwave satellite imagery.
The Great Storm of 1975 was an intense storm system that impacted a large portion of the Central and Southeast United States from January 9 to January 12, 1975. The storm produced 45 tornadoes in the Southeast U.S. resulting in 12 fatalities, while later dropping over 2 feet (61 cm) of snow and killing 58 people in the Midwest. This storm remains one of the worst blizzards to ever strike parts of the Midwest, as well as one of the largest January tornado outbreaks on record in the United States.
The characteristics of United States rainfall climatology differ significantly across the United States and those under United States sovereignty. Summer and early fall bring brief, but frequent thundershowers and tropical cyclones which create a wet summer and drier winter in the eastern Gulf and lower East Coast. During the winter, and spring, Pacific storm systems bring Hawaii and the western United States most of their precipitation. Low pressure systems moving up the East Coast and through the Great Lakes, bring cold season precipitation to from the Midwest to New England, as well as Great Salt Lake. The snow to liquid ratio across the contiguous United States averages 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water.
The climate of Houston is classified as a humid subtropical climate, with tropical influences. August normally ranks as the warmest month at 84.6 °F (29.2 °C) and January the coldest month at 53.1 °F (11.7 °C).
Traditionally, areas of tropical cyclone formation are divided into seven basins. These include the north Atlantic Ocean, the eastern and western parts of the northern Pacific Ocean, the southwestern Pacific, the southwestern and southeastern Indian Oceans, and the northern Indian Ocean. The western Pacific is the most active and the north Indian the least active. An average of 86 tropical cyclones of tropical storm intensity form annually worldwide, with 47 reaching hurricane/typhoon strength, and 20 becoming intense tropical cyclones, super typhoons, or major hurricanes.
Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms.
The climate of the United States varies due to changes in latitude, and a range of geographic features, including mountains and deserts. Generally, on the mainland, the climate of the U.S. becomes warmer the further south one travels, and drier the further west, until one reaches the West Coast.
Thermal lows, or heat lows, are non-frontal low-pressure areas that occur over the continents in the subtropics during the warm season, as the result of intense heating when compared to their surrounding environments. Thermal lows occur near the Sonoran Desert, on the Mexican plateau, in California's Great Central Valley, in the Sahara, in the Kalahari, over north-west Argentina, in South America, over the Kimberley region of north-west Australia, over the Iberian peninsula, and over the Tibetan plateau.
The North American monsoon, variously known as the Southwest monsoon, the Mexican monsoon, the New Mexican monsoon, or the Arizona monsoon is a pattern of pronounced increase in thunderstorms and rainfall over large areas of the southwestern United States and northwestern Mexico, centered roughly on the Rio Grande Valley, and typically occurring between June and mid-September. During the monsoon, thunderstorms are fueled by daytime heating and build up during the late afternoon and early evening. Typically, these storms dissipate by late night, and the next day starts out fair, with the cycle repeating daily. The monsoon typically loses its energy by mid-September when much drier conditions are reestablished over the region. Geographically, the North American monsoon precipitation region is centered over the Sierra Madre Occidental in the Mexican states of Sinaloa, Durango, Sonora and Chihuahua.
The 2015 Pacific hurricane season is the second-most active Pacific hurricane season on record, with 26 named storms, only behind the 1992 season. A record-tying 16 of those storms became hurricanes, and a record 11 storms further intensified into major hurricanes throughout the season. The Central Pacific, the portion of the Northeast Pacific Ocean between the International Date Line and the 140th meridian west, had its most active year on record, with 16 tropical cyclones forming in or entering the basin. Moreover, the season was the third-most active season in terms of accumulated cyclone energy, amassing a total of 290 units. The season officially started on May 15 in the Eastern Pacific and on June 1 in the Central Pacific; they both ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Northeast Pacific basin. However, the formation of tropical cyclones is possible at any time of the year. This was shown when a tropical depression formed on December 31. The above-average activity during the season was attributed in part to the very strong 2014–16 El Niño event.
A Gulf of California moisture surge, or simply gulf surge, is a meteorological event where a pulse of high humidity air is pushed up the Gulf of California. Gulf surges bring moisture to southern Arizona during the North American Monsoon. Prior to the 1970s, the consensus of meteorologists was the moisture that fueled the central and southern Arizona monsoon resulted from the movement of the Bermuda High to a more south and west position, which in turn transported water vapor to the region from the Gulf of Mexico. However, operational meteorologists in the 1970s described episodic surges of moisture that infiltrated the area that was thought to originate in the Gulf of California. It was noted that these episodes were likely to be associated with a convective system near the tip of the Baja peninsula such as a tropical cyclone or an easterly wave.
Hurricane Dolores was regarded as the worst hurricane to strike Acapulco since 1938. Developing on June 13, 1974, the system rapidly organized into a tropical storm the next day off the southern coast of Mexico. Over the following day, Dolores developed an eye-like feature and attained hurricane status. With peak winds of 80 mph (130 km/h), the storm made landfall near Acapulco. Once onshore, Dolores rapidly dissipated and was last noted on June 17.
References
- ↑ "Wind Names".
- ↑ "The Arizona Monsoon".
- ↑ Hales, John E (1975). "A Severe Southwest Desert Thunderstorm: 19 August 1973". Mon. Wea. Rev. 103 (4): 344–351. Bibcode:1975MWRv..103..344H. doi: 10.1175/1520-0493(1975)103<0344:ASSDTA>2.0.CO;2 .
- ↑ Mohave Daily Miner, Sep 2, 1984.https://news.google.com/newspapers?nid=943&dat=19840902&id=EIALAAAAIBAJ&sjid=S1MDAAAAIBAJ&pg=3278,11733
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