hail hail form solid precipitation distinct american called ice outside united_states confused consists balls irregular ice called ice falls generally cold weather hail growth greatly cold surface temperatures unlike ice smaller translucent consist water ice measure millimetres centimetres diameter reporting code hail greater smaller coded hail possible thunderstorms produced nautical miles parent storm hail formation requires environments strong upward motion air parent thunderstorm similar tornadoes lowered heights freezing level mid latitudes hail forms near interiors continents tropics tends confined high elevations methods available detect hail producing thunderstorms weather satellites weather radar imagery generally fall higher speeds grow size factors melting friction air wind interaction rain slow descent earth atmosphere severe weather warnings issued hail stones reach damaging size cause damage human structures commonly farmers crops definition thunderstorm produces hail reaches ground known hail diameter millimetres grow centimetres weigh kilograms unlike ice layered irregular hail composed transparent ice alternating layers transparent translucent ice millimetre thick deposited travels cloud suspended aloft air strong upward motion weight falls ground diameter hail varied united_states average observation damaging hail golf ball sized stones larger usually considered large cause damage issues severe thunderstorm warnings hail size expected national_weather_service greater diameter threshold effective january increase previous threshold hail countries different according local sensitivity hail instance growing areas adversely impacted smaller large small depending strong weaker produce smaller stronger formation hail forms strong thunderstorm clouds particularly intense high liquid water content great vertical extent large water good portion cloud layer freezing types strong indicate presence tornado growth rate air near temperature layer nature like precipitation clouds hail begins water rise temperature goes freezing water freeze contact cross section large shows like structure means thick translucent layers alternating layers thin white theory suggested subjected multiple falling zone humidity motion thought responsible successive layers new research based theory field study shown necessarily true storm directed wind speeds high miles hour blows forming cloud passes areas cloud concentration humidity water varies growth rate changes depending variation humidity water encounters rate water factor growth moves area high concentration water captures translucent layer area water available layer white ice furthermore speed depends position cloud mass determines varying layers rate water depends relative water means generally larger form distance stronger pass time growing grows releases heat keeps exterior liquid phase undergoes wet growth outer layer sticky single grow collision smaller forming larger entity irregular shape rising thunderstorm mass longer supported minutes based force hail producing thunderstorm usually greater high falls ground continuing grow based processes leaves cloud later begin melt passes air freezing temperature unique trajectory thunderstorm sufficient explain layer like structure case multiple discussed thunderstorm ejected mother cell captured intense daughter cell exceptional case factors favoring hail hail common continental interiors mid latitudes hail formation considerably likely freezing level altitude feet movement dry air strong thunderstorms continents increase frequency hail promoting cooling freezing level thunderstorm clouds giving hail larger volume grow accordingly hail common tropics despite higher frequency thunderstorms mid latitudes atmosphere tropics tends warmer greater altitude hail tropics occurs mainly higher elevations hail growth small air temperatures fall water rare temperatures thunderstorms hail likely cloud elevations feet feet feet percent hail thunderstorm percent lies clear air feet hail equally distributed thunderstorm distance nautical miles hail occurs frequently continental interiors mid latitudes common tropics despite higher frequency thunderstorms mid latitudes hail common mountain ranges mountains force horizontal winds upwards known lifting intensifying thunderstorms making hail likely higher elevations result time available hail melt reaching ground common regions large hail mountainous northern india reported highest hail related death tolls record china experiences significant southern australia experience lot popular regions southern western germany northern eastern france southern eastern south eastern europe croatia serbia experience frequent occurrences hail north_america hail common area colorado nebraska wyoming meet known hail region occurs months march october afternoon evening hours bulk occurrences september wyoming north_america hail prone city average season short term detection weather radar useful tool detect presence hail producing thunderstorms radar data complemented knowledge current atmospheric conditions allow determine current atmosphere hail development modern radar angles site values multiple angles ground level storm proportional precipitation rate levels gives liquid water content cloud research shows hail development upper levels storm related evolution divided vertical extent storm called density relationship hail size varies atmospheric conditions highly accurate traditionally hail size probability estimated radar data computer based research include height freezing level estimate melting left ground certain patterns important clues body spike example result energy radar hitting hail ground hail radar energy took time hail ground opposed energy went direct hail radar echo away radar actual location hail radial path forming cone weaker recently properties weather radar returns analyzed differentiate hail heavy rain use differential formula combination horizontal formula led variety hail classification visible satellite imagery beginning detect hail false alarm rates remain high method size terminal velocity size best determined measuring diameter ruler absence ruler size visually estimated comparing size known objects coins objects eggs comparing sizes varied dimensions organisation scales observed airport code surface weather observation relates size code indicate larger hail diameter inches derived french word smaller sized hail snow use short french word hail records large rocks ice associated thunderstorms officially recognized hail ice associated thunderstorms records extreme characteristics given hail records heaviest bangladesh april largest diameter officially measured inches diameter inches july largest officially measured inches inches diameter aurora nebraska june terminal velocity hail speed hail falling strikes ground varies estimated diameter falls rate metres second mph stones size centimetres diameter fall rate metres second mph velocity dependent size stone friction air falling motion wind falling collisions melting stones fall warmer atmosphere hail stones perfect spheres difficult speed accurately hazards hail cause damage notably automobiles aircraft glass structures livestock commonly farmers crops hail damage roofs goes unnoticed structural damage seen leaks cracks hardest recognize hail damage roofs flat roofs roofs hail damage detection problems metal roofs fairly resistant hail damage accumulate damage form damaged hail significant thunderstorm hazards aircraft exceed inches diameter planes seriously damaged seconds accumulating ground hazardous landing aircraft hail common drivers automobiles severely vehicle cracking shattering windows wheat corn tobacco sensitive crops hail damage hail canada expensive hazards rarely massive known cause fatal head trauma cause costly deadly events history earliest known incidents occurred 9th century india died injuries hail size cricket balls largest terms diameter weight recorded united_states fell july measured inches diameter inches weighing pounds broke previous record diameter set inches diameter inches greatest fell aurora nebraska united_states june record weight set pounds fell kansas narrow zones hail ground association thunderstorm activity known hail streaks hail satellite storms pass normally minutes minutes duration accumulating hail storms blanket ground inches hail cause thousands lose power bring trees flash flooding mudslides areas steep terrain concern accumulating hail depths reported landscape covered accumulated hail generally resembles covered accumulated snow significant accumulation hail restrictive effects snow accumulation albeit smaller area transport infrastructure accumulated hail cause flooding blocking drains hail carried turning snow like deposited lower elevations somewhat rare occasions thunderstorm stationary nearly producing hail significant depths accumulation occur tends happen mountainous areas july case foot hail accumulation colorado june hail feet deep fell city block denver colorado described size bees balls accompanied rain high winds hail fell area leaving surrounding area untouched fell half hours national_weather_service boulder said interesting phenomenon saw storm stall produced amounts hail small area meteorological thing clear area filled dump truck loads hail research focused individual days accumulated inches hail minutes colorado range shown events share similar patterns observed weather radar lightning characteristics suggesting possibility predicting events prior occurrence fundamental problem continuing research area unlike hail diameter hail depth commonly reported lack data leaves researchers forecasters dark trying verify operational methods cooperative effort national_weather_service summer progress joint project goal enlist help general public develop database hail accumulation depths suppression prevention middle ages people europe ring church bells fire cannons try prevent hail subsequent damage crops updated versions approach available modern hail cannons cloud world war eliminate hail threat particularly soviet_union claimed percent reduction crop damage hail storms achieved deploying silver clouds rockets artillery shells hail suppression programs undertaken countries
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