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WEATHER

WEATHER. Adapted from Skračić ,T., „ Waypoint ”. Glossary :

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WEATHER

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  1. WEATHER AdaptedfromSkračić,T., „Waypoint”

  2. Glossary: weatherconditions, high / lowpressure, windbelts, localpatterns, barometer, weathersystems, anticyclone, depression, clockwise, anti-clockwise / counter-clockwise, moveeastward / westward, upward / downward, at sealevel, onshorewind, down-slopewind, saturatedair, fog, dew, deadcalm, breeze, gale, storm, hurricane, seacondition, ripples, waves, crests, spray, foam, impairedvisibility,climate, hinterland, mainland, coastalarea, maestral (NW), tramontana (N), burin (NE), bura (NE), levant (E), jugo (SE), lebić (S-SW), pulent(SW-W), calm / roughsea, gust, thunder, coastal radio station, harbourmaster’s office.

  3. RadiantenergyfromthesunheatstheEarth's surfaceunevenlysothattheatmosphereis warmerin some placesthaninothers; sincewarmair is lessdensethancoldair, itrises. • Cold airsinks to replaceitandvariationsaboveandbelowaveragepressureoccurresultinginregionsofrelativelyhighandlowpressure. • Air alwaysmovesfrom a regionofhighpressureto one oflowerpressure – but notdirectlybecausethemovement is deflectedbytherotationoftheEarth. Theflowofair is felt as windwheneverthere is a differenceinatmosphericpressurebetweentwolocalities; itsstrengthis determinedbythe rate of change inpressurebetweenthetwocentres.

  4. Variationinbarometric • pressure is one ofthesailor's principleindicationsofimpendingchanges to windandweatherinhisarea. In general, whenthebarometer is steady, or risingsteadily, thisindicatesfairweather. Ifit is fallingslowly, thisindicatesrain, possiblywind. Whenthebarometeris fallingor risingrapidly, thisindicatesstrongwind – probablyrain.

  5. Highsandlows • Anticyclonesanddepressions (highsandlows) are thetwomainweathersystemsofthemiddlelatitudes. Inthenorthernhemisphere, ananticyclone is a systemwherewindsblowin a clockwisedirectionaroundareasofhighpressure. Thestrongestwindsblowroundtheouterextremitiesoftheareaandgraduallydiminishinstrengthtowardthe centre wherethey are light or non- existent. Anticyclones are fairweathersystemswithmoderatewindsandreasonablyclearskies. They are generallyslowmoving, sometimesremainingstationary for severaldays. Depressionsandtheirassociatedfronts are largely • responsible for unsettledweather, strongwindsandheavyrainfall. A depression is anareaoflowpressurearoundwhichthewindsblowinananti-clockwisedirectioninthenorthernhemisphere. Theyvarygreatlyinsizeandintensityandcanmoverapidlyinanydirection but most usuallyeastward.

  6. Localwinds • Wind is movingaircreatedby temperature differences. Localwindsinvariousforms are a modification to the general weatherpatternbut stemfromthe same basiccause. Seabreezesdevelopincoastalareawhenconvectionovertheland on a warmsunnydaycausesstrongupwardcurrentsofair. Therisingairis replacedbyaninflowofairfromovertheseawhichcreatesanonshorewind.

  7. At night • At nighttheprocess is reversedandthelandbreezeoccurs. TheEarthcoolsquicklyaftersunsetwhilethesearetainsits temperature andsoair is drawnofftheland to replacethewarmairrisingfromoverthesea.

  8. Katabaticwind • Inareaswherethecoastline is more dramaticandcloudlessskiesat nightresultinradiationcoolingoftheland, a strong, down-slopewindcandevelop as airincontactwiththegroundbecomeschilledandflowsrapidlydownthehillside.

  9. Fogandseafog • Fogcanform at any time ofyear. Itoccurswhenwarmmoistair is cooledsufficiently to becomesaturatedandcondenseintowatervapour. Seafog (advection) occurswhenwarmmoistairflowsover a relativelycoldseasurfaceandthe temperature oftheairincontactwiththissurface is lowered. Ifthesea temperature is belowthedewpoint temperature oftheairandcoolingcontinuesuntiltheair is saturated, condensationwilltake place andformmist or fog.

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