A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
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.
A severe thunderstorm warning is a severe weather warning product of the National Weather Service that is issued by regional offices of weather forecasting agencies throughout the world to alert the public that severe thunderstorms are imminent or occurring. A severe thunderstorm warning is issued when Doppler weather radar, trained storm spotters or local emergency management personnel indicate that a thunderstorm is producing large hail and high winds capable of causing significant damage, and is expected to continue producing severe weather along the storm's projected track. Flooding is also sometimes caused by torrential rainfall produced by a thunderstorm.
Hurricane Opal was a large and powerful Category 4 hurricane that caused severe and extensive damage along the northern Gulf Coast of the United States in October 1995. The fifteenth named storm, ninth hurricane and strongest tropical cyclone of the unusually active 1995 Atlantic hurricane season, Opal developed from the interaction of a tropical wave and a low-pressure area near the Yucatán Peninsula on September 27 as Tropical Depression Seventeen. The depression crossed the Yucatán Peninsula and intensified into a tropical storm on September 30. Opal intensified into a hurricane on October 2 after entering the Gulf of Mexico. The cyclone turned northeastward and strengthened significantly. By October 4, Opal was an intense 150 mph (240 km/h), Category 4 hurricane. With a minimum pressure of 916 mbar (hPa), Hurricane Opal was the most intense category 4 Atlantic hurricane on record. However, the cyclone abruptly weakened to a low-end Category 3 hurricane prior to making landfall on the Florida Panhandle near Pensacola later that day. The storm quickly unraveled as it moved inland and became extratropical on October 5. The remnants of Opal moved northward and dissipated over Ontario the following day.
Severe storms in Australia refers to the storms, including cyclones, which have caused severe damage in Australia. For comparison, a comprehensive list of all damaging storms can be found on the Australian Bureau of Meteorology website.
A particularly dangerous situation (PDS) tag is enhanced wording first used by the Storm Prediction Center (SPC), a national guidance center of the United States National Weather Service, for tornado watches and eventually expanded to use for other severe weather watches and warnings by local NWS forecast offices. It is issued at the discretion of the forecaster composing the watch or warning and implies that there is an enhanced risk of very severe and life-threatening weather, usually a major tornado outbreak or a long-lived, extreme derecho event, but possibly another weather hazard such as an exceptional flash flood or wildfire.
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. Extreme weather phenomena that cause extreme heat, cold, wetness or drought often will bring severe weather events. One of the principal effects of anthropogenic climate change is changes in severe and extreme weather patterns.
Extreme weather events in Melbourne, Australia have occurred on multiple occasions. The city has experienced a number of highly unusual weather events and extremes of weather. An increase in heat waves and record breaking temperatures in the 21st century has led to much discussion over the effects of climate change in the country.
On August 4, 2009, at 9:25 am EDT a major thunderstorm producing large hail and winds in excess of 60 mph (97 km/h) advanced at the leading edge of a cold front moving across the American Midwest, causing a flash flood that struck Louisville and portions of the surrounding Kentuckiana region. The National Weather Service estimated that between three to six inches of rain fell across the city in less than one hour, breaking all previous one-hour rainfall records in the area. Most of the downtown area was underwater, with the deluge reaching four feet (1.2 m) deep in places. The flood was the third major disaster to strike the region in less than one year.
The 2010 Western Australian storms were a series of storms that travelled over southwestern Western Australia on 21 and 22 March 2010. One of the more intense storm cells passed directly over the capital city of Perth between 3:30pm and 5:00pm on Monday 22 March 2010. It is the costliest natural disaster in Western Australian history, with the damage bill estimated at $1.08 billion.
The global weather activity of 2010 includes major meteorological events in the Earth's atmosphere during the year, including winter storms, hailstorms, out of season monsoon rain storms, extratropical cyclones, gales, microbursts, flooding, rainstorms, tropical cyclones, and other severe weather events.
Tropical Storm Hermine was a near-hurricane strength tropical cyclone that brought widespread flooding from Guatemala northwards to Oklahoma in early September 2010. Though it was named in the western Gulf of Mexico, Hermine developed directly from the remnant low-pressure area associated with the short-lived Tropical Depression Eleven-E in the East Pacific. Throughout its lifespan, the storm caused 52 direct deaths and roughly US$740 million in damage to crops and infrastructure, primarily in Guatemala. The precursor tropical depression formed on September 3 in the Gulf of Tehuantepec and neared tropical storm intensity before making landfall near Salina Cruz, Mexico, on the next day. Though the depression quickly weakened to a remnant low, the disturbance crossed the Isthmus of Tehuantepec and tracked north into the warm waters of the Gulf of Mexico, where it reorganized into a tropical cyclone once again on September 5. There, the system quickly strengthened into a tropical storm and received the name Hermine before moving ashore near Matamoros, Mexico on September 7 as a high-end tropical storm. Over the next few days, Hermine weakened as it moved over the U.S. Southern Plains, eventually dissipating over Kansas on September 10.
The 2010 Victorian floods were a widespread series of flood events across the state of Victoria, Australia. The floods, which followed heavy rain across southeastern Australia in early September 2010, caused the inundation of about 250 homes, hundreds of evacuations and millions of dollars of damage. Weather warnings were initially issued for Victoria on Thursday 2 September and rain began to fall on the Friday, continuing through the weekend to Tuesday. Heavy rain fell in most regions of the state, particularly at higher altitudes in the state's west and northeast, flooding the upper reaches of many of Victoria's major rivers. A state of emergency was declared with State Emergency Service crews arriving from Queensland, South Australia and Tasmania. The floods proceeded an extensive drought period that had effected the entirety of Australia.
Australian rivers have been subject to devastating floods in New South Wales, recorded since colonisation. Flooding in New South Wales has predominately been caused by excessive flows into rivers located in New South Wales and, to a lesser extent, excessive flows into rivers located in Queensland and Victoria. Floods can devastate local communities and impact the entire local economy.
High intensity rainfall between 12–14 January 2011 caused major flooding across much of the western and central parts of the Australian state of Victoria. Several follow-up heavy rainfall events including Tropical Low Yasi caused repeated flash flooding in affected areas in early February in many of the communities affected by January's floods.
The Montreal flood of 1987 happened on July 14 of that year when a series of strong thunderstorms crossed the island of Montreal, Canada, between the noon hour and 2:30 p.m. Over 100 millimetres (3.9 in) of rain fell during this very short period of time. The sewer systems were overwhelmed by the deluge and the city was paralyzed by the flooded roads. Autoroute 15, a sunken highway also known as the Décarie Expressway, soon filled with water, trapping motorists. Some 350,000 houses lost electricity, and tens of thousands had flooded basements. Two people died, one in a submerged car and another who was electrocuted.
The July 1968 United Kingdom thunderstorms were the most severe dust fall thunderstorms in the British Isles for over 200 years. A layer of mineral dust blowing north from the Sahara met cold, wet air over the British Isles, resulting in thick, dense clouds and severe thunderstorms across most of England and Wales. These clouds completely blotted out the light in some areas and the rain and hail resulted in property damage and flooding, and at least four people were killed. During the storm, Leeming Bar in North Yorkshire saw 35.7 millimetres (1.41 in) of rain in under 10 minutes – a UK record until 2003.
A Black nor'easter is a persistent and potentially violent north-easterly storm that occurs on the east coast of Australia usually between late spring and early autumn, about two days a year, although not a convection wind, but a storm system that develops offshore which can last several days. This is heralded by the rapid build-up of dense black cloud that can convert to a gale in well under one hour, and also bringing with it a heavy rainfall event usually accompanied by a thunderstorm. This type of storm was first recorded during the 1800s.
From February to April 2019, widespread flash flooding affected large parts of Pakistan, most severely in Balochistan, KPK, Punjab, and other provinces. Pakistan has been hit by three major waves of rain and flooding over the course of more than one month. The first wave of rain began on 20 February, leading to flooding in to Khyber and Balochistan, therefore many villages and several cities have been evacuated, and more than 1,500 families has been rescued alone in Balochistan and many in other states. The 20 February rain and thunderstorms caused flash floods in the Lasbela area. The main areas affected were Turbat, Tump, Nasirabad and Dasht where 300 people were displaced due to the flood. These people were then moved to camps established by the Provincial Disaster Management Authority (PDMA). Casualties have came mostly due to roof collapsing amid heavy rains and flash flooding. Khyber Pakhtunwkha has witnessed the most deaths till now, 40, alongside Balochsitan has faced 26 casualties with more than 9 in Punjab and other places. Due to rain, flood and storm casualties are increasing.
Severe storm events in Sydney, New South Wales, Australia are not uncommon and include hailstorms, wind storms, and flash flooding from rain caused by East coast lows, black nor'easters and/or tropical cyclone remnants. East coast lows are low pressure depressions or extratropical cyclones that can bring significant damage by heavy rain, cyclonic winds and huge swells. Sydney is rarely affected by cyclones, although remnants of cyclones do affect the city.
