Foghasrecentlybecomeafrequenthigh-impactweatherphenomenonalongthecoastalregionsofNorthChina.Accuratefogforecastingremainschallengingduetolimitedunderstandingofthepredictabilityandmechanismoffogformationassociatedwithsynoptic-scalecirculation.Onefrequentsynopticpatternoffogformationinthisareaisassociatedwithcoldfrontpassage(cold-frontsynopticpattern,CFSP).ThispaperexploredthepredictabilityofatypicalCFSPfogeventfromtheperspectiveofanalyzingkeycharacteristicsofsynoptic-scalecirculationdeterminingfogforecastingperformanceandthepossiblemechanism.TheeventwasensembleforecastedwiththeWeatherResearchandForecastingmodel.Twogroupsofensemblememberswithgoodandbadforecastingperformancewereselectedandcomposited.Resultsshowedthatthepredictabilityofthiscasewaslargelydeterminedbythesimulatedstrengthsofthecold-frontcirculation(i.e.,troughandridgeandtheassociatedsurfacehigh).Thebad-performingmemberstendedtohaveaweakerridgebehindastrongertrough,andassociatedhigherpressureoverlandandaweakersurfacehighoverthesea,leadingtoanadverseimpactonstrengthanddirectionofsteeringflowsthatinhibitwarmmoistadvectionandenhancecolddryadvectiontransportedtothefocusregion.Associatedwiththiscolddryadvection,adversesynopticconditionsofstratificationandmoistureforfogformationwereproduced,consequentlycausingfailureoffogforecastinginthefocusregion.Thisstudyhighlightstheimportanceofaccuratesynoptic-scaleinformationforimprovedCFSPfogforecasting,andenhancesunderstandingoffogpredictabilityfromperspectiveofsynoptic-scalecirculation.
