FrontsFronts

By 2/O John JaromahumBy 2/O John Jaromahum

FrontFront

A front is defined as the transition zoneA front is defined as the transition zonebetween twobetween two air massesair masses of differentof differentdensity. Fronts extend not only in thedensity. Fronts extend not only in thehorizontal direction, but in the vertical ashorizontal direction, but in the vertical aswell. Therefore, when referring to thewell. Therefore, when referring to thefrontal surface (or frontal zone), wefrontal surface (or frontal zone), wereferring to both the horizontal and verticalreferring to both the horizontal and verticalcomponents of the front.components of the front.

AirmassAirmass

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Warm FrontWarm Front

A warm front isA warm front isdefined as thedefined as thetransition zonetransition zonewhere a warm airwhere a warm airmass ismass isreplacing a coldreplacing a coldair massair mass

rise, then steadyrise, then steadysteadysteadysteady risesteady riseDew PointDew Point

fair in hazefair in hazepoor, butpoor, but

improvingimprovingpoorpoorVisibilityVisibility

usually none, sometimesusually none, sometimeslight rain or showerslight rain or showers

drizzle or nonedrizzle or nonelightlight--toto--moderate rain,moderate rain,

snow, sleet, or drizzlesnow, sleet, or drizzlePrecipitationPrecipitation

clearing with scatteredclearing with scatteredScSc; occasionally; occasionally CbCb

in summerin summerstratusstratus--typetype

in this order:in this order: CiCi,, CsCs, As,, As,NsNs, St, and fog;, St, and fog;

occasionallyoccasionally CbCb ininsummersummer

CloudsClouds

slight rise, followed byslight rise, followed byfallfall

leveling offleveling offusually fallingusually fallingPressurePressure

warmer, then steadywarmer, then steadysteady risesteady risecoolcool--cold, slow warmingcold, slow warmingTemperatureTemperature

southsouth--southwestsouthwestvariablevariablesouthsouth--southeastsoutheastWindsWinds

After PassingAfter PassingWhile PassingWhile PassingBefore PassingBefore Passing

Cold FrontCold Front

A cold front is defined asA cold front is defined asthe transition zone wherethe transition zone wherea cold air mass isa cold air mass isreplacing a warmer airreplacing a warmer airmass.mass.

Cold fronts generallyCold fronts generallymove from northwest tomove from northwest tosoutheast. The air behindsoutheast. The air behinda cold front is noticeablya cold front is noticeablycolder and drier than thecolder and drier than theair ahead of it. When aair ahead of it. When acold front passes through,cold front passes through,temperatures can droptemperatures can dropmore than 15 degreesmore than 15 degreeswithin the first hour.within the first hour.

loweringloweringsharp dropsharp drophigh; remainshigh; remains

steadysteadyDew PointDew Point

good, except ingood, except inshowersshowers

poor, followed by improvingpoor, followed by improvingfair to poor infair to poor in

hazehazeVisibilityVisibility

showers thenshowers thenclearingclearing

heavy rains, sometimes with hail,heavy rains, sometimes with hail,thunder and lightningthunder and lightning

short period ofshort period ofshowersshowers

PrecipitationPrecipitation

CuCuCbCbincreasing:increasing: CiCi,, CsCs

andand CbCbCloudsClouds

rising steadilyrising steadilyminimum, then sharp riseminimum, then sharp risefalling steadilyfalling steadilyPressurePressure

steadily droppingsteadily droppingsudden dropsudden dropwarmwarmTemperatureTemperature

westwest--northwestnorthwestgusty; shiftinggusty; shiftingsouthsouth--southwestsouthwestWindsWinds

After PassingAfter PassingWhile PassingWhile PassingBefore PassingBefore Passing