Thunderstorm Avoidance

Thunderstorrm AvoidanceOnline Course e Ref: C137-2 C-OL-C Page 1/13 Rev: 2 Date 15/08/2 2014 TAB BLE OF CONTENT LEGAL CAUTION .... C ....................................................................................................................................................... 3  DEFINITIIONS .................................................................................................................................................................. 3  ANVIL............................................................................................................................................................................................. 3  BOW ECHO O .................................................................................................................................................................................... 3  CONVECTIV VE OUTLOOK ................................................................................................................................................................ 3  DERECHO ....................................................................................................................................................................................... 3  DOWNDRAFT ................................................................................................................................................................................. 3  EXTRA-TRO OPICAL CYCLO ONE .......................................................................................................................................................... 3  GUST FRON NT ................................................................................................................................................................................. 3  MESO-SCALLE CONVECTIV VE SYSTEM .............................................................................................................................................. 3  MESO-SCALLE INFORMATTION .......................................................................................................................................................... 4  METEOROLLOGICAL IMPA ACT STATEMEN NT (MIS) ........................................................................................................................... 4  ROLL CLOU UD ................................................................................................................................................................................. 4  SEVERE THUNDERSTORM H MS ............................................................................................................................................................ 4  SHELF CLO OUD ................................................................................................................................................................................ 4  SUPER-COO OL LIQUID WATER A  ......................................................................................................................................................... 4  UPDRAFT ........................................................................................................................................................................................ 4  CLOUD TYPES ......... T ....................................................................................................................................................... 4  HIGH-LEVEEL CLOUDS ..................................................................................................................................................................... 5  MID-LEVELL CLOUDS ...................................................................................................................................................................... 5  LOW-LEVEL CLOUDS ..................................................................................................................................................................... 5  THUNDER RSTORM ST TAGES OF DEVELOPM D MENT .................................................................................................... 6  CUMULUS STAGE .......................................................................................................................................................................... 6  MATURE STAGE ............................................................................................................................................................................ 6  DECAYING STAGE ......................................................................................................................................................................... 7  THUNDER RSTORM TY YPES ............................................................................................................................................. 7  SINGLE CELL ................................................................................................................................................................................. 7  THUNDERSSTORM CLUSTEER (MULTI CELL E ) ................................................................................................................................... 7  SQUALL LINE I  ................................................................................................................................................................................ 7  SUPERCELLL .................................................................................................................................................................................... 7  HAZARDS TO AVIAT TION ............................................................................................................................................. 7  TORNADOEES .................................................................................................................................................................................. 7  TURBULEN NCE ................................................................................................................................................................................ 8  ICING .............................................................................................................................................................................................. 8  HAIL ............................................................................................................................................................................................... 8  LOW CEILIN NG AND VISIB BILITY ....................................................................................................................................................... 9  EFFECT ON N ALTIMETERS................................................................................................................................................................ 9  LIGHTNING G .................................................................................................................................................................................... 9  ENGINE WATER A INGESTIION ........................................................................................................................................................... 9  GROUND D-BASED WE EATHER RA ADAR ...................................................................................................................... 10  STRENGTH OF RADAR RETURN E  .................................................................................................................................................... 10  ECHO INTEENSITY (REFLEECTIVITY) ............................................................................................................................................... 10  INTENSITY OF PRECIPITA ATION ..................................................................................................................................................... 10  WSR-88D MODES ....................................................................................................................................................................... 10  RADAR REFFLECTIVITY ................................................................................................................................................................. 10  BASE REFLLECTIVITY .................................................................................................................................................................... 10  Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. Ştii. A rights reserved. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Şti. ..... 12  DOS AND DON’TS FOR THUNDERSTORM H M PENETRATIO ON .................................................................................................................................... AS ITS NAME N IMPLIES S.................................................................................................................................... 10  GROUND RADAR INFORM MATION—FLIG GHT PLANNING G .......................................................................................................................................... A rights reserved....................................................................... 11  DOS AND D DON’TS OF F THUNDER RSTORM AV VOIDANCE ................................................................................ 11  DATA LINK K OF GROUND RADAR INFOR RMATION TO THE T COCKPIT .............................................................. 11  AIRBORNE WEATHER AVOIDANCE RAD DAR IS............................................ Şti............................................................................... 11  INTENSE OR R EXTREME ECHO C AVOIDAN NCE ...................Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 2/13 Rev: 2 Date 15/08/2 2014 COMPOSITEE REFLECTIVITTY ................. ....................................................................................... 11  AIRBORNE WEATHER RADAR A ECHO AVOIDANCE ................................................................................................................................... 11  DOS BEFOR RE ENTERING A STORM ...... No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd................................ Ştii................................................... FOR AVOIDIN NG SEVERE WE EATHER—NOT T FOR PENETRATIING IT ................. 11  THUNDERSSTORM AVOIDA ANCE ............................................................................................. 13  Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd............................................................................................................................................................................................. 11  AIRBORN NE WEATHE ER RADAR ................ usually acccompaniedd by precipitattion as in a shower or thunderstorm t m. loccal and com mpany regullations and it is to be used for trraining purpposes only.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 3/13 Rev: 2 Date 15/08/2 2014 LEGAL CA AUTION The mateerial contained in this training prrogram is based b on thhe informattion obtaineed from currrent state. . straigght-line winndstorm thaat is associated with a ffast-moving thundersttorms. Convectiive Outlook k A categoorical forecaast issued as a a narrativve and a grraphic by the t Nationaal Weather Service (NWS) Storm Prrediction Ceenter (SPC)). Downdraaft A small--scale coluumn of airr that rapiidly sinks toward thee ground. and noormally perrsists for seeveral hourrs or thundersttorms but smaller more. alongg with “highh pressure”” systems. spreading top t of a cum mulonimbuss cloud. Thundersttorm anvils may spread huundreds of miles m downw wind from the t thunderstorm itselff. drive d the weathher over muuch of the Earth. Şti. ofteen shaped liike an anvil. Mooderate. long--lived.” Exxtratropical cyclones c are typical “llow pressurre” systems that. andd High Risk. DEFINITIIONS Anvil The flat. Inn the eventt of conflicct between data provided herein and that in publications isssued by the authority. Ştii. Extra-tropical Cycllone t as “mid-llatitude cycclones. A rights reserved.” These are defi fined as syn noptic scale low Are moree commonlyy referred to pressure weather syystems that occur in thhe middle laatitudes of the t Earth (ooutside the tropics) haaving neither trropical nor polar charaacteristics. Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. At the tim me of designingg this proggram contained then current c info ormation. soometimes asssociated with w a shelf clouud or roll clloud and maay also be reeferred to as an outflow w boundary. Extra-tropiccal cyclonees are typicaally associaated with frronts and horizzontal gradiients in tem mperature annd dewpointt otherwise known as ““baro-clinicc zones. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. A microb burst is the result of a sstrong down ndraft. Meso-scaale Convective System m A complex of multiiple thundeerstorms thaat becomes organized on a scale larger than n the indiviidual s thann extra-troppical cyclon nes. and somettimes may spread s upwiind. Gust Froont The leadiing edge off gusty surfa face winds from f thundeerstorm dow wndrafts. the t authorityy shall take precedencee. Derecho g band of seevere A widesppread. E produucing anyth hing from cloudiness c aand mild sh howers to heeavy gales andd thunderstoorms. which sppecifies the perceived level l of thrreat for con nvection viaa the descriptivve wording:: Slight. Bow Ech ho Radar echho that is linnear but bennt outward in i a bow sh hape. thus differentiiating them from the more m familiar shelf clou uds.” Roll Clou ud A low. and/oor tornadoes.layerr. Unlike the roll cloud. aand movem ment. horizontal h t tube-shaped d cloud asssociated wiith a thundderstorm guust front. If thee air is suffficiently moist. and “Nim mbo”-rain. liquid l waterr can survivve at tempeeratures colder than 0 degrees C. Şti. Roll R cloudss are relativelyy rare.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 4/13 Rev: 2 Date 15/08/2 2014 Meso-scaale Informaation An analyysis of meteeorological informatioon pertainin ng to atmosspheric phenomena haaving horizoontal scales rannging from a few to sevveral hundred kilometeers (km). Updraft A small--scale curreent of risingg air. high. prrecipitation n. m then tthe moisturre condensees to become a cumulus cloud c or an individual i tower of a to owering cum mulus or cuumulonimbu us. The T MIS is disseminate d ed and stored as a “repllaceable pro oduct. especcially for compplex situatioons. MIS pro oducts are numbered sequentiallly beginninng at midnightt local time each day. pact Statem ment (MIS)) Meteorological Imp marily for ATC A traffic m managers. The MIS is time-limiited to not exceed a 48-hour 4 vaalid period. . Ştii. “Sttrato”. p and thhose A non-tecchnical plaiin languagee product inttended prim involved in planningg aircraft rooutings. When the forecast iss no longerr descriptivve of expected conditions. the area and a altitudess affected. they are compleetely detachhed from thee thunderstoorm base orr other clou ud features. the MIS should s be uppdated. "Altoo”. This discussion will includee specifics such as what (weather) ( is causing thee disruptionn. Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. CLOUD TYPES T The folloowing cloudd roots andd translationns summariize the com mponents off the classiffication sysstem: “Cirro”-ccurl of hair. horizontal h w wedge-shap ped cloud associated a with w a thunnderstorm ggust front.mid. Shelf Clooud A low. pilots. using a specific Web addreess and will provide a brief desscription off the weather that is included in thhe text MIS. Thee MIS may refer to ann online graaphic. thhe shelf clooud is attaached to thhe base of the parent cloud aboove it whicch is usuallly a thundersttorm. T rms Severe Thundersto Thundersstorms that produce haail one inchh in diametter or largeer. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Super-coool Liquid Water W In the atm mosphere. many vigoorous storms coontain largee amounts off super-cooled liquid water w at coldd temperatuures. convectiive winds of o 50 knotss (58 miles perr hour) or grreater. A rights reserved. Thhe MIS conttains a brief discussionn of meteorrological evvents that couldd cause a disruption off the safe flow of air trraffic. Duue to cold troppospheric teemperatures at these levels. with cloud axees indicatingg localized areas of asccending. which h could beccome “bounndary-layer”” based andd can be releaseed into deepp convection during thee afternoon or evening. feathery. cirrus clo ouds tend too thicken innto cirrostrattus. A rights reserved. Alltocumulus clouds with h some vertiical extent m may denote the presencce of elevated instability. Ştii. thhen nimbosstratus resuulting in rain or snow. and often apppear thin. d icee crystals. thhicken and lower l into altostratus. veil-like v layyer (similar to what strratus clouds do d in low levels).000 feeet. allthough theiir names aree derived frrom "strato--" or "cumuulo-"... includiing super-ccooled dropplets (i. . Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. Unlike ciirrus. Low cllouds occurr below 65000 feet. Like cirrrocumulus. thesse clouds may m be compposed of liq quid water droplets. and d even nimbostratus. • sttratus whichh develop hoorizontally and • cuumulus whiich develop vertically. givven the preffix "alto-". the light is dispersed or o refractedd in such a w way that a familiar rinng or halo mayy form. m in turn. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Mid-leveel clouds The basees of cloudss in the midddle level of o the tropo osphere. and normally consist c of liiquid water drooplets or evven super-coooled dropleets. drier d air. appear a betw ween 6.e. Altostratuus clouds are a "strato" type t cloudss (see below w) that posssess a flat aand uniform m type texturre in the mid-llevels. the clouds primaarily are com mposed of ice i crystals. except during d coldd winter storrms when ice crystals (and snow) coomprise mucch of the cloouds. Dependding on the altitude. orr a combinaation of the tw wo. cirrosstratus clouuds form moore of a widespread. Low-leveel clouds Low-leveel clouds are not given a prefix.. especially in the mornning. altostratus clouds themselves doo not produce significant precipitatioon at the surrface. Theyy frequentlyy indicate thhe approach h of a warm front and m may thicken n and lower into stratus. and verticaal temperatture structurre of the troposphere.e.0000 feet/6000 0 meters annd are givenn the prefix "cirro-".500 andd 20. The two main m types of mid-leveel clouds aree. m ii. • alltostratus annd • alltocumulus. They T also mayy line up inn streets or rows of cloouds acrosss the sky deenoting loccalized areas of ascentt and descent. which may. dependinng on their characterist c tics.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 5/13 Rev: 2 Date 15/08/2 2014 High-levvel clouds High-level clouds occcur above about 20. a s stratus. Finally. tim me of year. although sprinklles or occassionally ligh ht showers may occur froom a thick alto-stratus deck. l Whhen sunlighht or moon nlight passees through the hexago onal-shapedd ice crystals of o cirrostrattus clouds. As a warm fronnt approachees. andd clear zonees between rows r suggessting locally deescending. mo oist air. f andd composed d entirely of ice crystals. heap-liike clouds with convectivve elementss. The two main m types of low clouuds include. d Altocumuulus cloudss exhibit "ccumulo" typpe characteeristic in mid-levels. sttreaky. Şti. They often are the firstt sign of an approachin ng warm froont or an uppper-level jett stream. cirrocumulu c us clouds are a layered clouds perm meated withh small cum muliform lu umpiness. However. liquid dropplets whosee temperatu ures are beelow freezing). altocumulu us may aliggn in rows or streets of clouds. and white. Cirrrus clouds are a wispy. Cumuluus clouds aree all capablee of producing some seerious storm ms! THUND DERSTOR RM STAGE ES OF DEV VELOPME ENT Cumuluss Stage Thundersstorms deveelop when thhe atmosphhere has warrm. The interactioons betweenn the rising warm. i. and ice crystal c particles. For instannce. The faalling precippitation and d cool air froom the enviironment staart the initiaation of cool doowndrafts. Cloud too ground ligghtning usu ually begins when the pprecipitation n first falls from f the cloudd base. A rights reserved. resulting in lightningg and thundder. dismal. a Thesee clouds apppear frequeently in the atmospheree. As thhe air begin ns to condense it form ms a cumu ulus cloud. heigght and widdth. during this stage. As thee mature-staage thunderrstorm deveelops. The dow wndrafts are caused by the downw ward drag of o falling raain. Thhe convectiive cloud coontinues to grow upwaard. clumped toogether in a continuo ous distribuution. Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 6/13 Rev: 2 Date 15/08/2 2014 Stratus cllouds are unniform and flat. A cumuluus cloud thaat exhibits significant s v vertical development (bbut is not yeet a thunderrstorm) is caalled “toweringg cumulus””. . c warm ming the air. deep cuumulonimbu us cloud. horizonntal stratus. Thee cloud edgges. which w leadss to the secoond stage. S Mature Stage The matuure stage is characterizzed by the presence p off both updraafts and downdrafts within w the clloud. scattered cumulus clouds show wing little verttical growthh on an othherwise sunnny day used d to be term med "fair w weather cum mulus. moist aiir which risses into a bu uoyant plum me or in a series of convvective updrrafts.. icce-water mixx. Nimbostratu N us clouds are a generallly thick. in ndividual cloud c elements.. Low stratus s deckks are comm mon in winter in the manyy areas. inndicating th hat the clouud is composedd primarilyy of water droplets. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. it eventu ually cools and condensees. and lifft are preseent. This coold descendding air inn the down ndraft will often reacch the grou und beforee the precipitattion.e. The dow wndraft is strengthened s d by evaporatiive cooling. and groow verticallly.. forming an anvil shaape often att the top of the t troposphhere. the top off the resultiing cumulonimbus clo oud will staart to flatten ouut. a As the warm air within w the cloud c contiinues to risse. characterristic of “strrato”. Durring this maature stage. c Straatocumulus also can bee thought off as a layer of o cloud cluumps with thickk and thin areas. Ştii. causes it to rise. a thundersttorm produucing heavyy rain. The conddensation releases heaat into the cloud. d Thhe process continues c annd works too form a tow wering cum mulus cloud. are usually y sharp andd distinct. esppecially behhind a storm m system when w cold. eventuaally growinng above the freezing level l where suuper-cooled water dropllets and ice crystals exist. deense stratuss or stratoccumulus cloouds producingg steady raain or snow w. grray weatherr can lingerr for several hours or evenn a day or tw wo.. in tu urn. i.type clouds. produccing a gray layer of clooud cover w which may be b precipitattionfree or may m cause peeriods of ligght precipitaation or drizzzle. a clo oud electriffication occcurs within cumulonim mbus clouds duue to many collisions between b chaarged waterr droplet. the cuumulus clouud continuees to increasse in size.e. This. as the rainn is falling with w the dow wndraft. In contraast to layerred. moiist and coolling air resuult in the deevelopment of a processs of rising annd falling air. cumulus clouds c are more m cellular (individual) ( in nature. moistuure. In addition. then strrong updrafts can develoop in the cuumulus clouud leading to a maturre. If enough atmospheeric instability. In fact." althoough normallyy they simplyy are referreed to just ass cumulus or o flat cumuulus.. Precipittation beginns to form once the air rises r above thee freezing leevel. entters drier airr below thee cloud basee and evaporatees. characteriistic of “cuumulo” typpe clouds. Stratocum mulus clouds are hybbrids of layyered stratu us and celllular cumuulus. either aheead of or beehind a frontall system. Şti. have flat boottoms and rounded toops. their t name deppends on thhe degree off vertical deevelopment. and becausse the shado ow of the cloud c and rain cooled dow wndrafts redduce the tem mperature beelow the clooud. Thunderrstorms maay be isolaated from other o cloudds or embedded within othher cloud deecks. unnstable air. Ştii. Whille not everry thundersstorm contaains all hazzards. Thhe ice crysttal laiden cloud c appears filmy. presssure inside thee vortex is quite q low. it is i a “tornaddo”. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. when thee source of moisture m is cut c off. Meteorologists havee estimated that wind in i such a vortex v can eexceed 200 knots. a Indiviidual cells withhin the clustter may movve in one diirection whiile the wholle system m moves in ano other. Ice crrystals typiccally first appeear in the anvil. The line may bee too long to detour easilyy around andd too wide and a severe to t penetratee. Thundderstorm typ pes may be classified aas: Single Cell mmon) thunnderstorm cell c often deevelops on warm w and hhumid summ mer days. If the in ncoming airr has any initiaal rotating motion. b HAZAR RDS TO AV VIATION All thundderstorms have h condittions that are a a hazard d to aviatioon. IIf the cloud d does not reach the surfacce. d witth indistincct cloud ed dges. These T A single cell (or com m winds. m it offten forms an a extremelly concentraated vortex from the su urface well into the cloudd.” if it toucches a land surface. but b it may develop d in unstable u air far removeed from any front. Şti. or when w lifting g ceases THUN NDERSTO ORM TYPE ES Thundersstorms packk just abouut every weather w hazzard knownn to aviatioon. The cloud c beginns to collap pse becausee no additionaal latent heaat is releaseed after the cloud dropllets freeze. The deecay of a th hunderstorm m can also be innitiated wheen the precippitation witthin the storrm becomess too heavy for the updrafts to suppport. it is a “ffunnel cloudd. These hhazards occu ur in numeerous combinattions. Decaay often beegins when thee super-coolled cloud droplets d freeeze and the cloud conttain ice crystals. d and the low preessure generrates a funnel--shaped clouud extendinng downwarrd from the cumulonim mbus base.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 7/13 Rev: 2 Date 15/08/2 2014 Decayingg Stage The decaaying stage is characteerized by downdrafts throughout t the entire ccloud. Often it develops d onn or ahead of a cold front in moist. a whichh becomes more m prono ounced in thhis stage. or diffuse. Thhese can coover large areas. Supercelll A superccell is a single long-livved thunderrstorm whicch is responnsible for nnearly all off the signifiicant tornadoess produced in the Uniteed States annd for most of the hailsttones largerr than golf ball-size.” Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. A rights reserved. and if itt touches water. Squall Line L A squall line is a narrrow band of o active thuunderstormss. it iss not possiible to visuually determine which hazzards a thunnderstorm coontains. . w it is a “waterspout. Pilots may encouunter thundersttorms of different d sizze and typees. w cells mayy be severe and produce hail and microburst Thunderrstorm Cluster (Multii Cell) Thundersstorms oftenn develop inn clusters with w numero ous cells. The T strong winds w gatheer dust and debris. Tornadooes The mostt violent thuunderstormss draw air innto their clo oud bases with w great force. within the cloud occuurs betweenn updrafts and Outside the t cloud. maay precede a microbursst. Since the voortex extends well w into thhe cloud. Şti. at lower l tempeeratures. Supeer-cooled drops d above thee freezing level begin to t freeze. clear air turbulence t m be enccountered 20 may 0 or more miles m from the anvil cloudd edge. Super-cooled water freezes on impact withh an aircrafft. As the upward d current of o air cools to a temperatuure of about -15ºC. It is almoost impossibble to hold a constant altitude a in a thunderstoorm. T The resultan nt outflow may produce wind shearr. Icing w with relatively larrge droplet sizes and when w Updrafts in a thundeerstorm suppport abundaant liquid water carried above a the frreezing leveel. Stressses are leasst if the airccraft is held in a consstant attitude. Hail Hail com mpetes withh turbulencee as the greeatest thund derstorm haazard to airrcraft. The abundancce of large. and a severe thu understorm can destroy an a aircraft. and maaneuvering in an attemppt to do so greeatly increaases stress on the airccraft. Ştii. icing from m smaller drroplets mayy be rime or mixed rimee and clear. Thus. Gust frontss often movve far ahead (upp to 15 milees) of assocciated precippitation. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. A low-level turbulennt area is associated with w the gust front. Additionally A y. other dropps latch on and freeze to t it. A microburrst is a smalll-scale. Virgga. The dow wnward movving columnn of air in a typical th hunderstorm m is large. Forecast reportss for tornadoes indicate that atmospheric connditions are favorable for violennt turbulencce.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 8/13 Rev: 2 Date 15/08/2 2014 Tornadoees occur with w both isolated and squall linee thunderstoorms. The gust frontt causes a raapid and som metimes drastic change inn surface wiind ahead of an approaaching storm m. v Families of tornadoes have beeen observedd as append dages of thee main clouud extendin ng several miles m outward from the area of ligghtning and precipitaation. Once O a drop has frozen. thee amount off super-coolled water deecreases. super-cooleed water drroplets makees clear icinng very rapid between 0ºC and -15ºC. Clear icinng can occuur at any alttitude abovee the freezing level l but at high levelss. Abovee this level. Th hunderstorm m icing can be extremely hazardouus. so the haailstone groows-sometim mes into a huge icebaall. A rights reserved. shear s turbuulence is enncountered several s thouusand feet above and up to 20 miles m laterally from a seveere storm. a “roll ccloud” or “shelf “ cloudd” on the leadinng edge of the t storm marks m the topp of the extrreme turbullence zone. the remaining r water w vaporr sublimatess as ice crysstals. and encouunters can be b frequent in a clusterr of cells. nce Turbulen Potentiallly hazardouus turbulennce is present in all thunderstorrms. any clouud connecteed to a seevere thundersttorm may coontain hidden vortexess. . inttense downddraft that when w reachinng the surfaace. the microbursst. Strongest turbulence t a downdrrafts. spreadss outward in all directions from the downdraft d c center. the wateer may beco ome super-cooled. An airccraft enterinng a tornado vortex v is almost certaain to suffeer loss of control c and structural damage. Often. and in some s cases the most severe typpe of wind shear. Large hail h occurs w with severee thunderstoorms Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. streaks of o precipitattion falling from a thun nderstorm cloud c but not reeaching the ground. anny pilot inaadvertently caught on instrumentts in a thun nderstorm could c encounter a hidden vortex. severe stoorms. possibly some s distance from the storm coree. Eventuallly. Effect on n Altimeterrs Pressure usually fallls rapidly with w the approach of a thunderstorm t m. serious acccidents duee to lightninng strikes arre extremelyy rare. Upddrafts are present p in many m thundersttorms. Rain R at the surface s doees not meann the absencce of hail aloft. Engine Water W Ingeestion Turbine engines e havve a limit on o the amouunt of wateer they can ingest. The restricctions createe the same prooblem as alll ceiling annd visibility restrictionss. Lightnning has beeen suspecteed of ignitiing fuel vappors causing g an explossion. If thee updraft veelocity in th he thundersttorm approachhes or exceeeds the veloocity of thee falling raindrops. veery high conncentrations of water may occur. Hail maay be enco ountered inn clear airr several miles m from the thundersttorm. Ştii. If I the pilot does not receivve a correctted altimeter setting. Althhough the ex xact mechannism of these water-induc w ced engine stalls s has noot been deteermined. Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. partiicularly thosse in the deeveloping sttages. As hailsttones fall thhrough air with w temperratures abov ve 0ºC. even distant ones. there is no known operationaal procedurre that can completely y eliminatee the possibilitty of enginee damage/flaameout durring massivee water ingeestion. but the hazards h are increased when w associiated with the other thundderstorm haazards of turrbulence. haail. can disruppt radio coommunicatio ons on low w and meddium frequeencies. At the present p timee. theyy begin to m melt and prrecipitation may reach thee ground ass either haill or rain. lightningg intensity annd frequenccy have no simple as a rule. the haillstones fall. A rights reserved. and lighhtning that make preciision instrum ment flying virrtually impoossible. esspecially beeneath the anvil a of a large l cumuloniimbus. thhe altimeter may be more than 1000 feet in erro or.. Nearrby lightnin ng can blindd the pilot. falling g back to norrmal as the thuunderstorm passes. It is possiblee that these concentrations can bee in excess of the quaantity of waater that turrbine engines are a designeed to ingest. Ceiling aand visibilitty also mayy be restrictedd in precipittation and dust d betweeen the cloud d base and the t ground. renndering the pilot momeentarily unaable to naviigate either by instrum ment or by visual v refereence. Thereforre. and a arrival of the cold downdraft and heavy rrain. Thhis cycle of pressure ch hange may occur in 155 minutes. it is i felt that thhrust chang ges may havve an adverse effect e on enggine stall margins m in thhe presence of massive water ingesstion. have a highh frequencyy of lightninng. Pressuree then usuallly rises shaarply with the onset o of thee first gust. a Pilots shoould anticippate possiblle hail withh any thund derstorm. Low Ceiling and Viisibility Generallyy. Lightnin ng A lightniing strike caan puncturee the skin off an aircraftt and can daamage comm municationss and electrronic navigatioonal equipm ment. Şti. severe th hunderstorm ms may coontain areass of high water w concentraation whichh could result in flameoout and/or sttructural faiilure of one or more en ngines. . Haillstones largeer than one--half inch in n diameter can c significcantly damag ge an aircraaft in a few secconds. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Lightn ning discharrges. however. visibilityy is near zeero within a thundersttorm cloudd.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 9/13 Rev: 2 Date 15/08/2 2014 with stroong updraftss that havee built to grreat heightss. Nearby lightning l caan also induuce permannent errors in the maggnetic comppass. Thoough s relattionship to other o storm parameterss. The scalle also inclludes ND correlated c too black thaat indicates “no data” was measuredd. Figure 4. the strronger the echo. Base Refflectivity Taken frrom the low west (½°) elevation e sccan. Echo Inttensity (Refflectivity) The coloors on radarr images reppresent diffferent echo intensities (also calledd reflectivitty) measureed in decibels of Z (dBZ)) (equivalennt reflectiviity). Thee scale rang ges from -330 to greater thhan 75 dBZ Z. defines thhis correlatio on. WSR-88D Modes M and P Precipitation n Mode. Reflectivity is also correelated with intensity teerminology (phraseology) for air traffic contrrol (ATC) purposes. thereforre. Ştii. A rights reserved. Whenn the dBZ Z value reaaches 15. Each VCP thereefore can provide a diifferent perrspective off the atmospheere. depictss these corrrelations fo or the WSR R-88D. WSR-888D Weathher Radar Prrecipitation Intensity Teerminologyy.. Intensityy of Precipiitation Reflectivvity is corrrelated to intensity of o precipitaation. Hailstones usually are a covered with a film m of water annd. WSR-88D Weather Radar R Echo Intensity Legeend. The dB BZ values increase i baased on the strength off the t atmosphhere. It iis composed d of the greatest echo inteensity (refleectivity) froom any eleevation anglle seen from m the radaar. These different d VC CPs have varying num mbers of eleevation tilts and rotation speeds of the t radar ittself. It is useed to reveall the Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. base reeflectivity is i excellentt for survey ying the reegion around thhe radar to look l for preecipitation. R Radar Reflectivity The radarr presents coverage in two t basic reeflectivity im mages. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. s Composiite Reflectiivity Utilizes all a elevationn scans duriing each vollume scan to t create thee image. Base reflecctivity imagge is the firsst image available duriing a volume scan. e Drop sizee determinees echo intennsity to a much m greaterr extent thaan does dropp concentration. act as huuge water drroplets givin ng the stronngest of all echhoes. G GROUND-B BASED WE EATHER RADAR R Strength h of Radar Return R Weather radar deteccts dropletss of precipitation. p T Table 1. . Şti. light precipitattion is pressent. Thhe greater thhe concentrration and/oor size of drrops. The hiigher the reeflectivity value. Each image inclludes a collor scale th hat represennts a return siggnal from targets in the correlatioon between intensity vaalue and coolor on the radar r imagee. thhe best knoown recom mmendation is to folloow the sev vere turbulence penetratioon procedurre containedd in the appproved Airplane Flight Manual (AF FM) with sp pecial emphhasis on avoidiing thrust chhanges unleess excessivve airspeed variations v o occur. During an unavvoidable enccounter witth severe stoorms with extrreme preciipitation. Wiithin There aree two main operating sttates of the WSR-88D:: Clear Air Mode these twoo operating states theree is volumee coverage pattern p (VC CP) forecastters utilize to help anaalyze the atmosphere arouund the raddar.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 10/13 Rev: 2 Date 15/08/2 2014 Avoidancce of severee storm systtems is the only measu ure assured to t be effecttive in preveenting expoosure to this typpe of multipple engine damage/flam d meout. The strength of o the radar return (ech ho) dependds on drop sizee and concenntration. v the higher h the rainfall rate. necessitaated by the need n for all elevation sccans to be completed c b before this im mage can bee produced. The abiility of airbborne weathher radar to detect weaather phenomeena is limiited in both directioon and ran nge. the radar r displaay provides no assurancce of avoiding turbulence. AIRBOR RNE WEAT THER RAD DAR Airbornee weather avoidance a radar is. Şti. may eexist when a cell absorbbs or reflects all a of the radio signalls sent by the t radar sy ystem. do not attem mpt to find a hole in a thundersto orm solely using u data-linked weath her..e.. such s echoess should be separated by b at least 40 miles befoore flying between b theem). Airbornee Weather Radar Ech ho Avoidan nce Remember that whille hail alwaays gives a radar r echo. a nk of Groun nd Radar Information I n to the Co ockpit Data Lin Unlike airborne a weather avoiddance radarr. c Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Thundersstorms buildd and dissippate rapidly. Ştii. weeather radaar detects only precipitattion drops. Compossite reflectiv in vity image is one of thhe last radaar image views. Intense or o Extremee Echo Avooidance Avoid heeavy or extrreme level echoes e by at a least 20 miles m (i. do not atteempt to plann a course between The best use of grouund radar innformation is i to isolate general areeas and covverage of ech hoes in order to avoid thee whole thunnderstorm area. A rights reserved. .. A phenom menon.. and the capabbilities of thhe pilot andd the aircraaft. Therrefore. As the cuurrent locattion of a thuunderstorm cell may be different tthan the bro oadcast weaather product..Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 11/13 Rev: 2 Date 15/08/2 2014 highest reflectivity r i all echoees. A suddden gust fro ont of low-llevel turbulencce could cauuse loss of control. Additiionally.” For aircraft equippped with aiirborne weaather radarr. weather data d linked from a groound weath her surveillance radar sysstem is not real-time innformation. Pilots may reducce the distance for av voiding weeaker echoes. foor avoidingg severe weeather—nott for penetratting it Whether to fly into an a area of raadar echoess depends on n echo intennsity. as a its name implies. The radar display alsoo does not provide p assuurance of avvoiding insttrument weaather conditionns from clouuds and fog. annd hazardouus turbulencee may extennd to as mucch as 20 miiles from thee echo edgee. Therefore. pilots shoould be fam miliar withh the operatingg techniquess and limitaations of thee specific sy ystem. The radar data displaays recent rrather than current c weaather conditionns. Avoidingg thundersttorms is the best policcy The folloowing are soome dos andd don’ts of thunderstor t m avoidancce: Don’t lannd or takeooff in the faace of an appproaching thunderstorrm. it does not detect turbuulence. Atteenuation maay prevent the radar from f detectingg additionall cells that might lie behind the first cell. DOS AND DON’TS OF D O THUND DERSTOR RM AVOID DANCE Thunderrstorm Avooidance Never reegard any thunderstorm t m lightly. calleed “attenuatiion”. it may fall several milles from thee nearest vissible cloud. This is oft ften referred d to as a radar r “shadow. Ground Radar Infoormation— —Flight Planning b echhoes. Pilots must m avoid inddividual storrms by visuual sighting or by airborrne weatherr radar. even e when radar obseervers repoort the echo oes are of light intensity.. spacinng between the echoes.. The au utomatic altiitude and speedd controls will w increasee maneuverss of the airccraft thus increasing strructural streess. that the route of flight is clear of thuunderstormss. Don’t atttempt to flyy under thee anvil of a thundersto orm. that you are a deviatingg for thund derstorms beefore acceptingg to rejoin thhe original route. put on thhe shoulderr harness (iff installed). Turn up cockpit c lighhts to highesst intensity to t lessen tem mporary bliindness from m lightning. There is a potentiial for seveere and extrreme clear air turbulence. This w will permit the t detectioon of other thunderstorm activity a at altitudes a other than the one being flown.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 12/13 Rev: 2 Date 15/08/2 2014 Don’t atttempt to flyy under a thhunderstorm m even if yo ou can see through to the other siide. Establishh power settings for turbbulence pennetration airrspeed recom mmended inn the aircrafft manual. If using automatic a pilot.. Scatteredd thunderstoorms not em mbedded usuually can bee visually cirrcumnavigaated. Don’t truust the visuaal appearancce to be a reeliable indiccator of the turbulence inside a thu understorm. Do ask ATC A for radaar navigatioon guidancee or to appro ove deviatioons around tthunderstorm ms. Do circum mnavigate the t entire arrea if the areea has 6/10 thunderstorrm coveragee. the follo owing are some s dos bef efore enterin ng the storm m: Tighten the t safety beelt.g. f Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. Do advisse ATC. If using airborne raddar. Do listenn to chatterr on the ATC A frequenncy for Pilot Weatherr Reports (P PIREP) and d other airrcraft requestinng to deviatee or divert. r Do ensurre that after an authorizzed weatherr deviation. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Flight F Inforrmation Serrvice-Broaddcast (FIS-B)) for route seelection to avoid a thunderstorms en ntirely (strattegic maneuuvering). Do avoidd by at least 20 miles any thunderstorm iden ntified as seevere or givving an inteense radar echo. Turbulence and windd shear undeer the storm m could be hazardous. disengage Altitudde Hold Mod de and Speeed Hold Moode. establish a penetratio on altitude below the ffreezing lev vel or abovee the To avoidd the most critical level of -15ºC. not where w the weathher is. Verify thhat pitot heaat is on and turn on carrburetor heaat or jet enggine anti-icee. whhen switchedd to anotherr controllerr. tilt thee antenna upp and down n occasionaally. Icing can be rapid att any altitude and a cause allmost instanntaneous power failure and/or loss of airspeedd indication. Plan and hold the coourse to takee the aircrafft through th he storm in a minimum m time. Do regardd as extrem mely hazardoous any thunnderstorm with w tops 355. Do use data-linked d weather NEXRAD N m mosaic imag gery (e. The weather coonditions may m be 15 to 20 minu utes older tthan the ag ge indicated d on the displlay. before acceepting to rejjoin the orig ginal route. t Don’t flyy without airborne a raddar into a cloud c masss containingg scattered embedded thunderstoorms. Do remem mber that viivid and freequent lightnning indicattes the probbability of a severe thun nderstorm. c icingg. c Do diverrt and wait out the thhunderstorm ms on the ground g if unable u to naavigate around an areea of thundersttorms. and secure all loose ob bjects. Ştii. . e This is esspecially truue under thee anvil of a large cumullonimbus.000 feet oor higher wh hether the toop is visually sighted s or determined d b radar. Don’t usee data-linkeed weather next generaation weath her radar (N NEXRAD) m mosaic imag gery as the sole means foor negotiatinng a path thrrough a thunnderstorm area a (tacticaal maneuverring). Dos Befoore Enterin ng a Storm If unable to avoid peenetrating a thunderstorrm. Don’t asssume that ATC A will offfer radar navigation gu uidance or deviations d arround thund derstorms. by Do give a PIREP forr the flight conditions. Şti. if needeed. Do remem mber that thhe data-linkked NEXRA AD mosaic imagery i shoows where tthe weatherr was. A rights reserved. . Şti. Allow A the alltitude and airspeed a to fluctuate. Inn addition.Thunderstorrm Avoidance Online Course e Ref: C-OL-C C137-2 Page 13/13 Rev: 2 Date 15/08/2 2014 Dos and Don’ts forr Thundersttorm Penettration Followinng are some dos and donn’ts during the thunderrstorm peneetration: Do keep your eyes on the fligght instrum ments. maintain m setttings for thee recommennded turbuleence penetraation airspeeed. A rights reserved. A straight course throough the stoorm most lik kely will geet the aircraft out o of the haazards most quickly. Look king outsidee the cockppit can incrrease dangeer of temporarry blindnesss from lightnning. Don’t chaange powerr settings. Do mainttain constannt attitude. tu urning maneeuvers increease stress on o the aircraaft. End of thhe course. Copyrights © 20 007 by Flyco Bilg gisayar Programc cılığı ve Eğitim Hizmetleri Ltd. Don’t turrn back oncce in the thuunderstorm. No All N part of this docum ment may be reproduc ced or copied in any form or by any mean ns without writte en permission of Flycco Bilgisayar Program mcılığı ve Eğitim Hizm metleri Ltd. Ştii.