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When you"ve completed this section, friend should be able to identify favorable geographical locations for thunderstorms in the united States and also worldwide, and discuss why coastlines and mountain ranges can be favorable areas for thunderstorms.


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Given the potential risks posed through lightning, room there any parts of the world that room immune native thunderstorms? no entirely, back some areas only hardly ever experience them. This map indigenous NASA showing worldwide lightning strikes native April 1995 to February 2003 (values are strikes every square kilometer per year) shows that lightning strikes (and therefore, thunderstorms) are common on six of the seven continents. Antarctica has actually very few lightning strikes (although castle do occur on rarely occasion), and areas end cooler oceans likewise experience lightning strikes fairly infrequently.

Thunderstorms often tend to it is in most constant over continents in locations where strong solar heating favors positively buoyant waiting parcels and also convection. The best frequency the lightning occurs end equatorial Africa, and other low-latitude floor areas likewise have reasonably high frequencies that lightning. In fact, some equatorial places experience thunderstorms ~ above about fifty percent the days every year, ~ above average.

In the united States, thunderstorms take place in every 50 claims as presented by the map that the average variety of "thunderstorm days" annually (below). Thunderstorms room most regular in the southeast U.S., particularly along the Gulf coastline from Louisiana to Florida. Thunderstorms space also reasonably frequent in the rest of the south east U.S. Into the great Plains the the U.S. (more than 50 days every year, ~ above average, through thunderstorms).


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The map showing the average number of "thunderstorm days" every year reflects that thunderstorms room most regular along the Gulf coastline in the southeast U.S. (especially in Florida). A relative maximum additionally exists over the main Rocky Mountains.

The constant occurrence the thunderstorms in the south-east U.S. Over toward the good Plains results from the continual presence of warm, moist maritime-Tropical air from the Gulf the Mexico. Particularly in the warmer months, this warm, humid air regularly favors positively buoyant waiting parcels that deserve to blossom into cumulonimbus clouds and also thunderstorms. But, this map has a pair of exciting features that I want to check out further. In particular, Florida bring away the trophy for many thunderstorms in the U.S., top top average, with components of Florida experiencing thunderstorms more than 100 days per year, ~ above average. Furthermore, there"s a curious preferably in thunderstorm frequency over the central Rocky mountains in Colorado and brand-new Mexico (60+ days every year through thunderstorms, top top average). You could not think of the Rockies as a "hotbed" for thunderstorms, however indeed, lock are! Let"s discover the reasons why thunderstorms are so regular in Florida and also the Rockies. Up first -- Florida.

Sea Breezes and Thunderstorms

The main reason for plenty of of the thunderstorms in the warmer months follow me the Gulf Coast and over Florida is a small-scale wind circulation called the "sea breeze." If you"ve ever noticed a strong, cooling onshore breeze that often establishes in the afternoon in ~ the beach, you"ve i found it the sea breeze! The sea breeze develops since of uneven heating between land and also water. On a sunny day, the soil warms more quickly than surrounding ocean waters, which causes the mean thickness of air columns over land to decrease slightly, i beg your pardon reduces the weight of neighborhood air columns and also reduces surface pressure. Meanwhile, the air end water stays cooler (and much more dense) and an area of high pressure creates offshore. These press differences cause low-level waiting to flow from the water come the land, generating an onshore wind dubbed the sea breeze. In order because that a sea breeze come form, the temperature difference in between land and water must be big enough to generate a adequate pressure difference between land and water, and also the job otherwise can not be also windy. If the day is windy before the sea breeze also develops, the winds will overwhelm the sea breeze.

The sea breeze is in reality a three-dimensional circulation, in which low-level air operation onshore, rises end land, and then operation offshore aloft (about one kilometer above the surface). But, the boundary between the cooler marine air flow onshore and the hot air over land (called the sea-breeze front), is a source of an excellent interest come weather forecasters since it acts like a miniature cold front, an interpretation that low-level convergence occurs follow me it as cooler wait pushes onshore. Low-level convergence follow me the sea-breeze front provides hot, humid waiting parcels on land an increase nudge, and sometimes that"s all they need. Their optimistic buoyancy takes over and off to the races they go, farming into cumulonimbus clouds and also thunderstorms.

The regular occurrence that sea breezes is a large reason behind the high frequency of thunderstorms follow me the Gulf Coast and Southeast shore of the U.S. But, why is Florida, in particular, such a element area because that thunderstorms? of course, wealth of warm, moist maritime-Tropical wait is a beneficial ingredient due to the fact that it favors positive buoyant waiting parcels. But, the schematic listed below tells the rest of the story. On sunny days with reasonably weak winds overall, there"s often not just one sea-breeze former in Florida; sea-breeze fronts push inland indigenous both the Atlantic ocean from the east and also the Gulf the Mexico from the west.


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Thunderstorms sometimes build over the Florida peninsula as sea-breeze fronts indigenous the Atlantic and Gulf coasts collide.

In addition, lakes and other smaller bodies that water can additionally create circulations similar to the sea breeze. In Florida, "lake-breeze" fronts have the right to push onshore native Lake Okeechobee, because that example. So, the combination of sea-breeze fronts and a lake-breeze front indigenous Lake Okeechobee means that there are boundaries galore in Florida, together this annotated visible satellite picture from may 5, 2007 shows. Every boundary has actually low-level convergence follow me it, and when these boundaries collide, the low-level convergence deserve to get even stronger, which gives air parcels a stronger press upward, initiating thunderstorms if the air parcels happen to be positively buoyant. To check out a genuine example, watch countless thunderstorms blossom end Florida on this loop of clearly shows satellite images from might 30, 2002. The corresponding radar loop mirrors the plenty of storms the developed, which carried heavy rain and hail. So, the constant presence of waiting parcels the can come to be positively buoyant and a plethora the boundaries and low-level convergence to give parcels a press upward makes Florida the thunderstorm (and lightning) funding of the U.S.!

High-Level Heat resource Thunderstorms

What around the preferably in thunderstorm frequency over the Rocky mountains in Colorado and brand-new Mexico? How could a mountainous an ar favor thunderstorm development? In a nutshell, that comes down to uneven heater again. On a sunny day v weak winds overall, as the sunlight heats the mountain, surface air in contact with the hill warms, leading to air thickness and, thus, air press to diminish (relative come the bordering "free atmosphere" not in call with the mountain).In this way, mountains serve as "high-level warmth sources," and also the resulting push gradient reasons air to move toward and also up the mountain as presented in the schematic below.


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As the sun heats the mountain, surface ar air in call with the hill warms, resulting in air thickness and, thus, air push to diminish (relative come the neighboring "free atmosphere" not in contact with the mountain). The resulting push gradient causes air to relocate toward and up the mountain, setting the phase for convection. In this way, mountains serve as high-level heat sources.

With air rising up the slopes that the mountain throughout the day, the hill peak i do not care a region ripe because that convergence and further uplift (as suggested by the schematic above). The convergence close to the mountain peak, then, offers air parcels a nudge upward, and also if they"re positive buoyant, thunderstorms have the right to develop. Thunderstorms creating over the mountaintops that the Rockies are much more common in the summer if the air flowing up the eastern sides the the hills is warm, moist wait from the Gulf that Mexico. When thunderstorms blossom near the hill peaks, they regularly drift off the hills (typically toward the east) depending on the winds aloft.

When hills act together high-level warmth sources, originally sunny days v weak winds in the Rockies regularly aren"t really sunny by afternoon. Because that example, ns took this picture in Rocky mountain National Park in Colorado top top an originally sunny day in August, 2006. As generally happens in the summer, numerous cumulus clouds developed throughout the afternoon, i beg your pardon eventually came to be thunderstorms. To see an instance on satellite, check out this succession of clearly shows satellite photos (from 12Z, 17Z, and 21Z ~ above July 7, 2001), and watch the cumulonimbus clouds develop. If you to compare the succession of photos with this relief map cropped come the same view, you"ll view that the thunderstorms occurred over the mountaintops.

So, there"s no doubt that topography deserve to play a crucial role in initiating thunderstorms, and that"s why thunderstorms are more frequent over components of the Rockies compared to their surroundings. You may additionally be wondering why relatively couple of thunderstorms occur west the the Rockies. The an easy answer is that the region lacks a resource of warm, moist air required for positively buoyant wait parcels. The Pacific s along the West coastline is actually relatively chilly, and as the cool air operation onshore, it tends to stabilize the atmosphere (favoring negative buoyant parcels). So, the instability needed for thunderstorms is less usual in the western U.S., leading to less frequent thunderstorms over there (the same deserve to be stated for parts of the north U.S., too).

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But, also though some locations experience less frequent thunderstorms, lock can happen all over in the united States and most land areas of the world. Opportunities are just around everyone has been impacted by a thunderstorm at once or another (if not numerous times!). If we want to learn more about thunderstorms, we should examine your anatomy and life cycle. We"ll start trying out those object in the following section.