Vodna tromba, imenovana tudi vodni tornado, vodni vrtinec ali v angleščini waterspout je podnebna tvorba, ki nastaja predvsem v poletnih dneh ob menjavi vremena. Lahko nastane kot posledica 'kopenskega tornada', najpogosteje pa se oblikuje nad morjem ob kroženju toplih in hladnih zračnih mas. 24.6.2013 s(m)o tudi obiskovalci slovenskega Pirana imeli možnost opazovati ta pojav.
Podrobnejša obrazložitev principa nastanka in delovanja vodne trombe:
Za nastanek vodnih tromb so potrebne tople (vlažne) in hladne zračne mase. Ko se tople mase iznad morja dvigajo nad hladne, se oblikuje vrtinčast 'sesalec', ki vleče navzgor kapljice morja. Sprva so ti vrtinci nevidni, ko pa vase posrkajo zadostne količine vlage in morja, jih opazimo kot 'mini' tornade. Načeloma takšne trombe niso nevarne, trajajo do 20 minut, premikajo pa se s hitrostjo 10 do 15 vozlov (18 do 28 kilometrov na uro).
Opis trombe Morske biološke postaje Piran; LINK
Vodna tromba nastane nad toplimi vodnimi površinami in je na videz podobna tornadu, le da so njeni vetrovi manj uničujoči. Trombe se pojavijo, ko nad plastjo toplega in vlažnega zraka, ki se nahaja nad vodno gladino, zapihajo hladni vetrovi. Pogosto se pojavljajo v skupinah. Vrtinčasti viharji so zelo različni in najmanjši se pojavljajo že na prašni cesti, ko veter zvrtinči delce zraka in se ti dvignejo nekaj metrov v višino. Nekateri so tudi večji, ti že lomijo drevje in odnašajo manjše predmete.
Veliki so tornadi, največji pa tropski cikloni (hurikani, tajfuni). Tudi na morju se naredi vrtinec, največkrat ob nevihtah in pri nas mu pravimo tromba na Hrvaškem pijavica, v angleščini pa waterspout. Trombe posrkajo tudi morske kapljice. Ob vrtinčenju dvignejo tudi večje količine morske vode in z njimi lahko tudi ribe. Če je tromba večja, je zelo nevarna manjšim plovilom.
Dodatno branje:
- http://www.mbss.org/portal/index.php?option=com_content&task=view&id=99&Itemid=9&lang=sl
- http://www.zurnal24.si/tromba-prestrasila-primorce-clanek-197880
- http://www.zurnal24.si/tromba-prestrasila-primorce-clanek-197880
Fotografije vodnih tromb (za večjo sliko, kliknite nanjo):
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| Vodna tromba, Piran 24. 6. 2013, Vir: Zurnal24.si |
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| Vodna tromba, Piran 24. 6. 2013, Vir: Zurnal24.si |
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| Vodna tromba, Piran 24. 6. 2013, Vir: Zurnal24.si |
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| Vodna tromba, Piran 24. 6. 2013, Vir: Zurnal24.si |
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| Vodna tromba, Hvar, 4. 8. 2006, Vir: Dnevnik.hr |
Še obrazložitev delovanja vodnih tromb (v angleščini):
To form, waterspouts need warm, humid air, as well as the cooler air provided by a cloud system. As a patch of warm air on the surface of the water rises, the cooler air around it begins to rotate. Because humid air over the water forms a copious amount of water vapor, and because this wet air is actually lighter than dry air, the water vapor swirls up into the air, cooling and condensing, becoming a "cascade" around the vortex. As the water vapor condenses into droplets, it releases more heat, increasing the vortex effect as it rises skyward. After a short time, the waterspout dissipates as the air within it cools. Waterspouts most often form during the warm season in tropical and subtropical waters. Dr. Joseph Golden, a waterspout expert with the National Oceanic and Atmospheric Administration (NOAA), says that the Florida Keys is where waterspouts occur more frequently than anywhere else in the world, though they have also occurred at higher latitudes, such as the Great Lakes and the Grand Banks off the coast of Newfoundland.
A Waterspout's Life Cycle
Dr. Joseph Golden has identified five stages of waterspout formation. Waterspouts are first evidenced by a raised dark spot on the surface of the water, usually only visible from the air. Though invisible, this indicates contact of a complete funnel of air between the cloud system and the water's surface. Then a spiral pattern of light- and dark-colored bands of water develops. When wind speed reaches around 40 mph, the spray vortex, or cascade, is formed, often rising several hundred feet into the air. Next, the fully visible waterspout reaches maturity and is seen reaching all the way from the ocean to the cloud. The final stage is decay of the waterspout, usually occurring as warm air feeding the waterspout dissipates, often cooled by rain showers developing from the cloud system.
A Waterspout's Life Cycle
Dr. Joseph Golden has identified five stages of waterspout formation. Waterspouts are first evidenced by a raised dark spot on the surface of the water, usually only visible from the air. Though invisible, this indicates contact of a complete funnel of air between the cloud system and the water's surface. Then a spiral pattern of light- and dark-colored bands of water develops. When wind speed reaches around 40 mph, the spray vortex, or cascade, is formed, often rising several hundred feet into the air. Next, the fully visible waterspout reaches maturity and is seen reaching all the way from the ocean to the cloud. The final stage is decay of the waterspout, usually occurring as warm air feeding the waterspout dissipates, often cooled by rain showers developing from the cloud system.
http://www.ehow.com/how-does_5661953_waterspouts-formed_.html
