Thunderstorm asthma is the triggering of an asthma attack by environmental conditions directly caused by a local thunderstorm. During a thunderstorm, pollen grains can absorb moisture and then burst into much smaller fragments with these fragments being easily dispersed by wind. While larger pollen grains are usually filtered by hairs in the nose, the smaller pollen fragments are able to pass through and enter the lungs, triggering the asthma attack.
A back-building thunderstorm, commonly referred to as a training thunderstorm, is a thunderstorm in which new development takes place on the upwind side (usually the west or southwest side in the Northern Hemisphere), such that the storm seems to remain stationary or propagate in a backward direction. Though the storm often appears stationary on radar, or even moving upwind, this is an illusion. The storm is really a multi-cell storm with new, more vigorous cells that form on the upwind side, replacing older cells that continue to drift downwind. When this happens, catastrophic flooding is possible. In Rapid City, South Dakota, in 1972, an unusual alignment of winds at various levels of the atmosphere combined to produce a continuously training set of cells that dropped an enormous quantity of rain upon the same area, resulting in devastating flash flooding. A similar event occurred in Boscastle, England, on 16 August 2004, and over Chennai on 1 December 2015
Severe Thunderstorm Warning VAC059-153-600-683-685-140130- /O.NEW.KLWX.SV.W.0529.190814T0058Z-190814T0130Z/
On August 19th, 2019 at 1:31 AM MDT, the National Weather Service in Cheyenne WY has incorporated the "emergency" wording to a Severe Thunderstorm Warning. This is unofficial wording that is used when an extremely intense Severe Storm impacts a largely populated location. In this case, 3 inch diameter hail was imminent for areas around both Scotts Bluff, and Gering, Wyoming.
* Severe Thunderstorm Warning for... The City of Fairfax in northern Virginia... Central Fairfax County in northern Virginia... The City of Manassas Park in northern Virginia... Central Prince William County in northern Virginia... The City of Manassas in northern Virginia...
BULLETIN - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Warning National Weather Service Baltimore MD/Washington DC 858 PM EDT Tue Aug 13 2019
At 129 AM MDT, a severe thunderstorm was located near Scotts Bluff National Monument, or near Scottsbluff, moving east at 40 mph. 3 INCH DIAMETER HAIL IS IMMINENT! PREPARE NOW FOR DESTRUCTIVE HAIL!
Here is an example of a Severe Thunderstorm Warning issued by the National Weather Service in Washington D.C. The audio file to the right is for Minnesota.
The following severe thunderstorm watch was issued for a large portion of the Northern Oklahoma and portions of Kansas and Missouri on April 25, 2017. URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 159 NWS Storm Prediction Center Norman OK 555 PM CDT Tue Apr 25 2017
...THIS IS A SEVERE THUNDERSTORM EMERGENCY FOR SCOTTSBLUFF AND GERING!...
* At 858 PM EDT, a severe thunderstorm was located near Bull Run, or near Centreville, moving east at 25 mph.
...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 215 AM MDT FOR SCOTTS BLUFF...NORTHEASTERN BANNER AND SOUTHEASTERN SIOUX COUNTIES...
REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes.
* Severe Thunderstorm Watch for portions of Southeast Kansas Western Missouri Central and eastern Oklahoma
The severe thunderstorm watch area is approximately along and 80 statute miles north and south of a line from 5 miles northwest of Oklahoma City OK to 50 miles north northeast of Joplin MO. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9).
URGENT - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 405 NWS STORM PREDICTION CENTER NORMAN OK 840 PM CDT MON MAY 30 2011 THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF PARTS OF NORTHWEST IOWA PARTS OF CENTRAL KANSAS MUCH OF EASTERN NEBRASKA SMALL PART OF SOUTHEASTERN SOUTH DAKOTA EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 840 PM UNTIL 200 AM CDT. ...THIS IS A PARTICULARLY DANGEROUS SITUATION... WIDESPREAD DAMAGING WINDS WIND GUSTS TO 90 MPH LIKELY SCATTERED LARGE HAIL ISOLATED HAIL TO 1.5 INCHES IN DIAMETER POSSIBLE ISOLATED TORNADOES THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTHWEST OF SIOUX CITY IOWA TO 50 MILES SOUTH SOUTHEAST OF RUSSELL KANSAS. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5). REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE TORNADOES. OTHER WATCH INFORMATION...CONTINUE...WW 402...WW 403... DISCUSSION...INTENSE SQUALL LINE HAS DEVELOPED N/S ACROSS CENTRAL NEB AND CONTINUES TO DEVELOP SWD AS IT MOVES EWD. VERY STRONG PRES RISE/FALL COUPLET IS DRIVING THE LINE EWD WITH THE FORCING FROM LARGE SCALE TROUGH ROTATING ACROSS THE NRN/CENTRAL PLAINS PROVIDING BOTH SHEAR AND UPWARD MOTION TO RESULT IN POTENTIAL FOR VERY DAMAGING WINDS. IN ADDITION BRIEF TORNADOES ARE STILL POSSIBLE BUT DAMAGING WINDS NOW ARE THE DOMINANT THREAT. AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 80 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR 23040. ...HALES
This term technically applies to a single thunderstorm with one main updraft. Also known as air-mass thunderstorms, these are the typical summer thunderstorms in many temperate locales. They also occur in the cool unstable air that often follows the passage of a cold front from the sea during winter. Within a cluster of thunderstorms, the term "cell" refers to each separate principal updraft. Thunderstorm cells occasionally form in isolation, as the occurrence of one thunderstorm can develop an outflow boundary that sets up new thunderstorm development. Such storms are rarely severe and are a result of local atmospheric instability; hence the term "air mass thunderstorm". When such storms have a brief period of severe weather associated with them, it is known as a pulse severe storm. Pulse severe storms are poorly organized and occur randomly in time and space, making them difficult to forecast. Single-cell thunderstorms normally last 20–30 minutes.
In the United States, a thunderstorm is classed as severe if winds reach at least 93 km/h, hail is 25 mm in diameter or larger, or if funnel clouds or tornadoes are reported. Although a funnel cloud or tornado indicates a severe thunderstorm, a tornado warning is issued in place of a severe thunderstorm warning. A severe thunderstorm warning is issued if a thunderstorm becomes severe, or will soon turn severe. In Canada, a rainfall rate greater than 50 mm in one hour, or 75 mm in three hours, is also used to indicate severe thunderstorms. Severe thunderstorms can occur from any type of storm cell. However, multicell, supercell, and squall lines represent the most common forms of thunderstorms that produce severe weather.
Any thunderstorm that produces hail that reaches the ground is known as a hailstorm. Thunderclouds that are capable of producing hailstones are often seen obtaining green coloration. Hail is more common along mountain ranges because mountains force horizontal winds upwards (known as orographic lifting), thereby intensifying the updrafts within thunderstorms and making hail more likely. One of the more common regions for large hail is across mountainous northern India, which reported one of the highest hail-related death tolls on record in 1888. China also experiences significant hailstorms. Across Europe, Croatia experiences frequent occurrences of hail.
Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of significant vertical wind shear, normally greater than 25 kn in the lowest 6 km of the troposphere, which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms, most commonly associated with large hail, high winds, and tornado formation. Precipitable water values of greater than 31.8 mm favor the development of organized thunderstorm complexes. Those with heavy rainfall normally have precipitable water values greater than 36.9 mm. Upstream values of CAPE of greater than 800 J/kg are usually required for the development of organized convection.