Severe Weather MET 4300
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This 35 page Class Notes was uploaded by Mr. Eladio Hettinger on Monday October 12, 2015. The Class Notes belongs to MET 4300 at Florida International University taught by Hugh Willoughby in Fall. Since its upload, it has received 44 views. For similar materials see /class/221788/met-4300-florida-international-university in Meteorology at Florida International University.
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Date Created: 10/12/15
Another Look at Supercells Vortex tilting forms counter rotating eddies flanking the updraft j39 5 Lowlevel inflow comes from 1 r ahead and to the right L 7 Midlevel inflow comes from 9 V the right and a little behind 4anltrquotT 39 Cross over and twist around each other Middle level inflow sweeps preoip behind the storm to form rearflank downdraft Lowlevel inflow becomes the anvil spreading downshear and drops preoip to for front flank downdraft Formation of Type II Tornadoes FIG 521 Diagram showing genesis of a nonmesocyclone tornado Wakimoto and Wilson 1989 Misoscale vortices identi ed by letters form along a windshift line black line as a result of shearing instability A tornado results from one of these vortices C being stretched by overhead convection Tornado family Harm tornado will develop here Storm motinn Tornado Path Length by FNumber Average Path Length km F0 F1 F2 F3 F4 F5 Fscale Tornado Occurrence by FujitaScale Number 1 um F4 i I 373 I 03 F5 I 255 Significant Tornado Alley 1 dayldecade 60 near peak Where Do Tornadoes Occur in the US Where Do Severe Tornadoes Occur When do Tornadoes Occur During the Day I a mum in mu 3 a s o a II 111234avasnuunusaunamnzn micsquot When Do Tornadoes Occur During Tornadoes by Vear US the Year 16 U 5 Tornados hyMoanDOSNOS MUD 12EIEI 1UEE 5 E Sun 3 z BEIEI 4 Observed Regressron 2mm o Ad1usted NIHquotI 195D 1955 196D 1965 197D 1975 19EE 1985 199D 1995 ZUUEI Year Is the Number of Strong to VIolent 7 Weather Fatalities Tornadoes 39 1968199530 year average Number of StlnnqrturVIulenl n5 Iumaduas no V Y 7 7 7 7 1 1 m 1 1w 1 1m i w 1 so 10 1 Ohm mu woo aw mm mu mm 0 1M mm mm 30ml n Flashr39md aod ng39llnmg Tanoda Immune USc Tornado Falalilies Tornados and Loss of LIfe Damage increases quotquotquotfj quotj quot 39w m rapidly with strength 6 i igmmm a WeakltF0F1 Ems u 74 of occurrences 4 of m g alhs n E 4 3 Z Strong F2 F3 25 of occurrences 29 of quotquot 39 39 h deaths Violent F4 F5 333 I run n u 1 of occurrences 67 of deaths n Ban gun 1920 I94EI gen 1950 2mm ear Bummun US Tm39narln DeathsMultan Fum mm mm w Tornado Impacts Economic damage corrected for e lh Totals 13 per decade or 100M per year Compared with 1OB per year from hurricanes Constant apart from economic scaling Loss of life 2030 year by 2006 Summary pa Turnadusfurm m supEmEHs Waugh vummtymung and retcmng umadu famH Successmn uftumadus m we same supemeu mstmctrurm moreaks pa H Turnadusfurm by stretcmng sheara ung uumuw n unda e 0 uftumadus are FEIFFZ 9 are FB 2 3 are FAFFE umadu AHEy Texas m Suum Dame urstmunm MAV Wurst we at new an FM tgnermumtunng has wen m mare tectmn gmuu Afear up rm mu m eany anus butfewerFA and F s1 a A amp F5 auumfur1 ufmmadus but 67 at u hs mpact1DUM and 2mm deaths peryear Much Ess nan humcanes rur damage but smeaHuss at We 242008 Airmasses amp Fronts AirmassLarge body of air with moreorless uniform properties such as temperature humidity stability Takes on these properties from the surface in a source region Front sharp almost discontinuous boundary between two airmasses Fronts generally move and cause disturbed weather as they pass in addition to changes of temperature and humidity mnum Pollquot Allmall mun ram Coat varn uquot nn nmhIVum k when Linnu Cal1 Dvyl l l l i V L v Canunnnlll I mpr r c Alumu v 1 mm Dryb i l minim anmul Almlnl u no quotHalal MIMI Maul hum Mum Mullquot Cold Front Structure Warrn less dense air ahead ofthe front overlies cold air Slope is typically 1100 Move fasterthan other kinds Abrupt cooling and veering of the wind from sw to N when the front passes entrance region ofletstreak or in downslope flow E of the Rocky MtsL Warm Front Structure Warm air behind the front overlies cold air I Slope is typically lt 1200 39 Move slower than cold fronts Gradual warmin veering of the wind from t e S to SW when the front asses onvection depends on stability and hu 39 f the warm air be we dofthe Most commonly steady rain and stratus clouds because the air is stable 242008 AA AA Unstable StatIonarv Fronts A A A A A rm menuquot A A AA mu A A A A A w mama A A AAAA AA A M A A AAAA WWW nnvmmnl gguslnlhewrm A AAA quot5 their A A A hnundlry A A r PmlpnIlnnnllsmlhe AA A A A a uum 7 7 i AA mnamm i A u 39 A A A 2A mm A Emam rm n Formation of Occluded Fronts Stable Stationary Fronts me um um mum or must 5 mm W gum vlhe nml m ce Drumming lrll nlm n nllslnmugmnevmmul m the frnm U pper Fronts upperleuel boundary between descending drvzir quot0m desensaud phlmus andzsczn m iairh lhEM Surface boundary between van u traslmdew pumt but ge erauy nutm temperature Dry 2v rs denser and runs underthe murst 2v mg the dry hne mwmter Afternuunthunderslurms are cummunmthe mmslzv n n tempemture comma Typical wintertime Pattern of Fonts m 242008 Summary Av Masses Budtes at atrwtth weHrde ned temperature and humtdtty denvedfmm a scarce regmn Frunts Bmmdanes b ween atrmasses Kmd uffrunt cum urWarm 5 de ned by thetemperature of the atrthat amves wtth tt Cu dfmnts are steeper and mwefasterthan warm hunts Una Front F awtsmust y paraHe wtththefmnt fa 7 Stab e Stratwarm ram ausmaug amt 5mm mm mm av D hne Surfacehumtdtty buundary upperant Boundary between nsmg mm mm mth and smkmg dry somewhat comer atr Ocduded Front we mm mtches up ta warm mm wedgmg a zyeruf mm atrupward FOR NEXT TIME No homework Read chapterg Exam Next Week We need to negotiate the da Lecture 3 stablllty Indlces 23 January 2003 Potential Temperature Condensation Start at some tem erature T1 and pressure Move along a dry adiabat to p 1000 mb Dry adiabat determined by temperature at sta pressure Mixing ratio determined dew point at starting pressure Follow dry adiabat and constant mix ng ratio until they intersect Lifting condensation level Or cloud base Moist adiabat above Air that moves Without condensation or diaba ic heating conserves lts potentlal temperature A Well mixed unsaturated Press ure 1000 ml before it was mixed Temperm ure EqUIvalent Potential Temperature Cloud Topped Mixed Layers start at some temperature T1 and pressure llFl1ove along a dry adlapat to the L CL Then follow a molst adlapat upward untll lt merges wllh a dry adlapat that ls parallel cloud base Both 9 and QEare constant below wllh lt Flnally follow that dry adlapat to 1000 mb 9539 COhStam through the Cloud to get Equivalent Potential Temperature layer Alrthat experlences condensatlon but no dlapatlc heatlng conserves lts potentlal Bur 9 39ncreases as a resu39t 0 5 temperature latent to senslble heat converslon Awell mlxed cloudy layer wlll have constant 7 V e lehquwalem porfemm relmpelrhar equahno Tand e lncrease ln the lnverslon g e average o e va ues a e alr before It was d as bafore g You can a proxlmate the EPT by followlng But es decreases becau a a molst a lapat from the Wet Bu p 1quot temperature u ward decreaslng humldlty across the V V Where It Intersects a dry adalpat from the mversmn surface ls the LCL Followmg the constant mlxlng ratlo back e approaches es at hlgh altltudes ggmn to he stamng pressure glves the new or wherever the a IS dry What Conditions Favor Convection Warm surface mixed Hu mixed layer Cold temperatures aloft Humidity aloft a a E i e Sometimes dry air aloft inhi mixing with the updraft and robbing it buoyancy e Sometimes dry air aloft favors convection by triggering downdrafts that start new cells snear is important too ts convection by 39 of woo i T so Mun sFEto sun MD minerals x ww swlgto3llnn1 swl ollnd Shnwus rumble swl n In 4 mneme swl rJIn sstmnv inmcnmn m swx swl es swx Vertical Totals Index VT Difference between temperatures at 850 mb and 500 mb VT T850 T500 A measure oflapse rate ues 25 Storms likel 30 Scattered thunderstorms a few severe gt 34 Numerous thunderstorms some severe possible tornadoes Cross Totals Index CT Difference between devvpulnt at 85D mb and temperature at am rnb VT Totasumsuu A measure Elf mulsture untent Vaiues lt l7 TR unilkeiy gt 3D NumeruusTR scattered SW and turnauues Total Totals Index TT sdm err VT cT VT Tmsu TDEsu72T5uu A measure ufbuth rhdrsrdre and instability Values lt 43 TR unlikely 7 44745 lsulated TR 7 46747 Scattered TR 7 48749 Scattered TR sdrhe swx 7 was Scattered rd hdrherdds heavy TR fevv svvx gt an Numeruus heavy TR seauered swx ahd turnadues K Index 39 TeamTDsdd TDdsdTrddTDrdd K gt 20 9 Chance ofAirMass thunderstorms K gt 40 9 Air Mass thunderstorms certain K gt 30 9 Potential for Mesoscale Convective Complexes Advantage does not require a plotted sounding Convective Available Potential Energy CAPE and cm are mere rhdderh rheasdres erslahrlrly ahd lns1ablllty CAPElstheamuuntulenergy lhal eah be released between the LFC and EL rh buuyam updra s Cletheenergymves nem requiredtuget utheLFC Units are rhIs Maximumpusslblevemcal velucny rs 2 x CAPE CAPE eah be as large as45u rrwr buttyplcally rs lsuu in 25mm Em dhslahle da s CAPE 25mm rhIs Works nut in a maximumvE lEai velocity ul7EI rhs u 39 marmastheadmadamewmrsm r We ar m we rmrur ems rramsr mm mm warmer warmer quotmade my ram manna 5w ALswue WEamer threat cuntInes n wnh drmaenees m mndhenweemhe xsn a 1Mquot m A Modern Sounding SUMMARY lhslahrmyravdrs eehveelreh rh lhe lrepesphere Shawn eh skew Lug p Diagrams Mere dhslahle lurwarmrmulst anhe surraee ahd eeel alu Rareel ascent 7 Ar rrses dry adrahalreallywnh eehslahl d in LCL 7 cedlerlhah ehvrrdhrhehnd LFC 7 Then hddyahl UMli it reaehes EL Stabllltym ees LlLSh rar rrwrr7rltpareeumerdha vr7 resumed er7 reread mun rr7 vro er K han camvlrcmed mamquot ma YD eAezraerNErerwMmerrmeweerarraarerwwsrmermsm Soundings and the Structure of Convective Clouds m a um a m canvnhan 396 w m mm Conanquot mum um 11 Cumulus Life Cycle cumums smummaw Auuvdvm man an Mayveachkmpev uves may mum caHivsmV mammmemay mum anmva aw mm mm nmunws Wm anlsthal mamggev new as s Alternative Entraining Jet Model Av mass m a corner Shaped updraft that draws m av around m From ansewamns me rama aws n1 xthe vemca ow a PuHsm massmcveasmg m amuum uMsmg aw Entraining Bubble Model C oud 5 made of mscrete huhh es Entramment ba ances detramment 50 sue Stays canaam DHutmn ofbuoyancyand momentum 5m occur Detramed mms mre mmstens envwronmem for next nunme Hydrometeors faH out of me bottomof each nunme Cumulonimbus Clouds are Often Collections of Bubbles individual bubbles farm at line base Rise thruugh the tuvver Luuse buuyancy as they enter the anvil cluud First bubble muisteri the envirunment furthE Either Limits dilutiuri er buuyancy With dry air Precipitation Formation claim in a Sunnrcaolud Cloud Wain Shear and new cell formation along outflow boundaries No She New nail is mm m men n Outflow Boundaries Dewndiaii anspieads anne suriaee Gust neni omnewpeundaw An claim eeweene lmpurtanttu running new cunvectiun Maintain idenmyieinems anei cunvectiun Deep cunvectiun in ggeied wnen uut uwbuun anes inieiseei Wthweaklurcing buundary inieiaeiienseeniiei inundeisieimieimaiien Shear and cell motion produce sloping updra s from which ydrometeors can fall causing displaced downdra s MidLatitude Squall Line Anatomy eeexsnem anvil an be nudn mare extensve Tornado Outbreak 7April2006 Warrn sectorof a frontal cyclone Tornadosi hall damaging ll ldS 12f liti Anvil m0 stly at isoac Overshooting cloudtopstor 7oa Multiple enhanced V signa ures Elliptical cold anvil characteristic of supercell amp tornadic storms Overshooting Tops Updralt still strong when it reaches its equilibrium level Negatively buoyant air penetrates through anvil to Then falls back Causes boiling cauli ower projections Most visible at low sun angle Tropical Squall Line 33mm a am From 39 mi mi Supercell Sounding mm Ml ll ov39ulm Haul i Supercell Dynamics Strung shear and powerful instabiiity CAP gt iann Snear causes sluping updrafts Hyururneteurs raii rrum updrafts and gran intu Hall urtuireritiai rain SD prEElpltatlEIn luading is less at a farm Crussirig midrlevel and surrace lriflUWS furrn fruntr and rear flank duwndra s FFD amp RFD Mesovortex Wall Cloud Mesoscale Convective Complex Weak synopticscale forcin Multicellular Several individual thunderstorms combine Form middlelevel Mesoscale Convective Vortex MCV Characteristics 7 Elliptical minor aXlSmal0l agtltl5gt0 7 MCC Life Cycle Ol39ogl39aphlcstorrns rorm overmountalns in late artemoon Many systems mergeto become MCCS Man don t Propagate east overthe l Reach maleUm SlZe around midnignt 7 When tne noctomal luwlevellet due to gradlents ufcuullng alung tne upslupe to me muuntalns lS strangest uslng tne llmatuluglcal rllghttlme maximum in rainrall e Abuut nalr caose heavy ralns ur uudlng vveallten arter midnignt tages r Initiate Flrs t sturrns El Euntlnuuus Eluud Shield that meets SlZE rlterla 7 Development Frurn initiation to maxlmum Size 7 Mature Maxlrnurn Extent until SlZE criteria no lunger met termination e Dissipating Termination untll new convection easestufurm What s really happening with MCCs Mesoscale Updraft Summary Parcel model of convection Air mass thunderstorm life 0 c e Entrainment intojets and bubbles limits growth and In e Precipitation processes Role of shear New cell initia ion at out ow boundaries sloping updra s avoid precipitation loading Be able to draw and ex 39 Middle latitude amp tropical squall lines Supercell thunderstorms MCCs Know the difference between MCCs and MCSs NEXT TIME Tornadoes Chapter 18 MET 4300 V What are M005 and MCSs MCS Mesoscale Convective System Any mesoscale weather feature that exhibits convective overturning MCC Mesoscale Convective ComplexMuch more restrictive Cloud tops colder than 3ZC over 100000 km2 r 180km AND Cloud tops colder than 520 over gt 50000 km2 r km p Both sizes last longer than 6 h Eccentricity 3 07 at maximum extent 9 BIA z 01 Properties First detected in satellite imagery Climatology derived from satellite tracking Produce significant beneficial growingseason rain over wheat amp corn belts Also cause locally intense rain and flash flooding Can cause tornadoes hail damaging wind lightening One in 4 causes injury or death Tend to move with the 700500 mb winds SIKllwwmml ilu n 4 m um um im mull1 mmm mi mi my mum MCC Tracks 1631 May 19781982 Ms May 1715 June 16730 June 145 July 1673mm Formation Form from Mergers of individual cells Old squall lines Many start where the plains rise to the foothills of the Rockies Preferred location shifts northward as season progresses Rare on East Coast and West of the Rockies Half form west of Lon 100 W half between 90 amp 100 and only a few east of 90W Stratifonn amp Convective Precipitation MCC Life Cycle Ovugvaphic stuvmslunn uvev muuntains in late attemuun ManysystemsmevgetubecameMCCs Many dun t Pvupagateeastuvevtheplains Reach maximumsize alum midnight 7 Whenthe nocturnal luwlevel let duetn giadients nt mnli g aiene the upsupemmemnumainsissmngesi 7 Causingthe dimatnlngical nighttimemaximum in vainlall 7 Abnuthaltcause heavvvainsnvllnnding Weaken alter midnight Sta 7 Inmate Fiva sturmstn mmmunus dnud stein that meets size criteria 7 neuannmmt me inniatinntnmaximum Sim 7 Mature Maximum extent until size cmevia rm lungeymeitieymmanen 7 l mllng Termination until newcnnvectinn eeases tn tnvm Musth over land Elongated belts in easterlies a maevlies Genemllv downstream ems mountains MCC Environmental Interaction Upperair data shows that MCCs warm and moisten their environmne Conditionally unstable atmosphere ahead of MCCs Veerin ofwind overnight increases warm in ow and in usx of unstable air Moist air around convective elements decreases downdraft strength and increases precipitation ef cienc Y MCCs die when they move into more stable environment High Windspeed Type 1MCCs Heavy Rainfall Type II MCCs Vlr 1quotl ll Flow in Type II MCCs n mm runwwclwmn m W mu 1 mil lx 4m Less shear More Circulation m What s Really Happening With MCCs Summary MCC s are long lasting large circular MCSs Form by coalescence ofindividual cells In North America the form E of the Rockies and drilt E or SE Des ite some severe weather the I rimaril I reduce bene cial rain High wind in sheared systems with little evident circulation Heavy rain in weaker shear and stronger cich a 39 IOI39IS Out ows combine to produce a circular cold pool with some in ow 39om SE Condensation in anvil and evaporation melting under it promotes convergence at the level ofthe ODC Isotherm which maintains the system quotquot 0 Yea Aieiage its 164 W Year More 49117 18 l l Wind Lightning l Hurricane Cold Tornado Heal Winter Storm Flood 492008 Annual Flood Losses 243 and 75100 Lives Flash oods are reported to kill 140lyear many in cars Kinds of Floods Flash Flood Short duration and limited area with little warning Most commonly due to slow moving thunderstorms usually in summer in the mountains orlparadoxically tlie esert Urban floods Heavy rain and blocked or overloaded storm drains back water up from streets into dwe ings Widespread Floods Cover major river basins ueto multiple extratropical cyclones rollowingtlie same storm rackmo en in springtime and may be aggravated by snowmelt Leisurly disasters Coastal Floods Rise of sea or lalltel level due to wind driven surge in addition to flooding from torrential rains It s rrloving waterthat s lethal Flood Occurrence By Month and Retrun Periods I mmnnwvm EEIEIIEEIB 9Mustrecurded rnontnly rain SEE ln July loot Cherrapungl india monsoon r ins eause rlooding or Gangesand Eirarnaputra 9Wursthlsturlcalfluuds Yangtz in iEEIiBEIE lair i935 iaao StiBSB claiming auuruuursuu nun liyes Each to total oro million e i a Meeru rrontlies oyertne Yangtze in spring and can drop a lgt or rain 492008 Levees Fiood St39e wit Evees 9Naturai Levees rorm through sedimentation on hver banks 9Amflclai levees augment the natural ones gtPrevent fioodwater retention upstream on the floodplain floodplain reairestate Coastal Floods Winds blow water onshore Hurricane Storm Surge is the largest US threat to life We forecast extent and depth using SLOSH or A CI Cnumericai models Evacuation based upon worstrcase modeiin increasingly accurate track forecasts has reduced the toil with the notable exception of atrina Inland ooding due to torrential rains has emerged another serious threat mumnmmnmmnm Satanourquot rm hInn Ian h n tm Total Precipitation from Tropical Storm Allison 4 June 18 June 2001 Placian in a MmImmanuannl uim39lnlmnnnw an am We mp lhauumlvnlllhml imm Miri 5 muIarjltm mum imi pt Ivrilm Mammy Nu mnmgunllclmmmill a 492008 Stationary Fronts and MCCs c u Feb 59 0000 um 4 Feb 991200 1m israaagoonnu 0 A iotof rain reaches me ground because of Staiionaryirontswim unstabie ai39r ahead are t at is Frontsgeneraiiydri ftSE over time mourn msmuns i i N Individual MCCs are large move Yb s ivrwaanvumnc slowly and may last a day or more i i 1 1 man mp annulus Vrnmlhe Gml mm mumquot n m Mllllly 35m in nunpa ma 1 deaths 24 W Ivme ummc i m 1 Great Flood of 1993 500w Event in Mississippi and its tributaries Damage 515205 4 Deaths 50000 homes desroved Stopped barge and rail transport 492008 25D mb qu anomaly EJUN a J Mean 25H m 59 mwmmm I mnmrmmmmnmlB Mum15M A Snowmelt and Ice Flash Floods in the Airid SW Dams Deserts lack vegetation to impede runoff Frequently mountainous Intermittent streams or quotArroyosquot Dw most of the I Springtime Rain on overwinter snow accumulation accelerates melting Waterways become clogged with ice restricting runof39f Summer monsoon brings sudden convective rain Can travel long distances downstream from storm Example Big Thomson flood of311uly 1976 I Dislodge suddenly 492008 Big Thomson Flood Eastsiooe of the Rockies ET drains onto oiains Neariy stationary mui ceH storrn deveiooed over the ET watershed Upsiooe conditionaiiy unstaoie ow in iow shear 39 CeHs Uai39ried over ET 39 Rained 6 in in 5 h 39 WaH of water 10715 ft high ciairned 39 hikers and pi39crii39ckers The Central Valley of California Waswetiand in mm thesir and a asweii sbyz st ievees Oniy drainageiswherethe Pineapple Express spin mm in mm N ew mun any as m u n mumng me me luck Flood Forecasting Numericai rnodeis tor gt 1 day pius sateiiite irnages For iargeascaie ooding persistence or a pattern Anaiysisorthe morningsounding39sstaoiii 7 a rrntotai or ioitationrecognize UainingMC s etc NOWCA we 2 1 5 E rri uuding Routineiy disruptive weather eg street ooding Annuzi oodimpzds SEBJSJOOMVES Kindsof oods FizshWidesprezdCozslzi Watersheds encampasstheiand drained by a stream and its tributaries Levees prdted a slrezm s ood piain from narrnai ooding Prmedion fed Fioodsczused byiongrizsling heavy rainraii e hurriahesthra hhothstarmsurgeandvretivitatian e Quasirstatianarv ants or siaw mam Mccs e riashiiaadsaused hvmummiithundemarms primariiyih deserts e CeHtrainingmnewteiishrminthesamDiamandmiawthesame tram Centrai Vaiiey at Caiirarnia andthe Pineappie Express Advisories e Watchr aadingiikziv e Warnin rimminginnihehtarhapvehire e Nawasingmhradarahd sateHite MET 4300 182008 Weather Elements Temperature we will use C Pressure mb of hPa Moisture Humidity or We or dimensionless Clouds Type and dimensions Hydrometeors Rain drizzle hail graupel Wind m 5391 Related to pressure in different ways for different scales Temperature Scales m m iuiiivu a mu quot m Wxmuammm u 5 i m quotnaumuyumum are 17 w uwmmpm u o 9 unnummm in i m l l l louuiumpauurzretumnd 7 M i c It F12H e n y H m w yinvath in 0 K56 m s sunmam Aimnspnm 5 an E 25 a v Stratosphere 20 i i E 2 1s Twpapause 5 LI Tmpbspher o 1sn zuu 210 In 230 2w 2m 2er 71 280 no son Worldwide Temperatures in January 21 A 7 5 r 182008 How the Earth39s OrbitAffects Temperature High and Low Latitude Temperature Varia ions Izn y Nyala Sudan 12 N a is Temperature F a FairbanksAlaska165 fl m rt Mar Apr May Jun Jui a Sup Dc rm De stratosphere trcpapause 39 srm mm Sim troposphere cm r r so Emirrm I Imwlruiwru Presssllg re as a Function of Height in Mr V r w mew TERM sub no plessure imm denslly In the Large Scale Atmosphere Pressure is the Weight of Air Above mm m um um ii How a Mercury Barometer Works Air presses on Hg in the dish Weightongin coiurnnis thesameastheweightof 6 air Vacuum atmetop orme tube SinceTorriceHi 1644 observers have identi ed iowpressurewi bad weather 182008 Humidity I Vapor Pressure The pressure due to HZO gas by itself Saturation Air holds all the moisture that it can for a given temperature I Relative Humidity Ratio ofthe mass of water in the air to the mass it could ave at saturation 8 Jan 2008 1745 UTC 39 I39ll LoluAIthzmIn Precip39tation Variation of Dew Point With Temperature I Waterthat falls from clouds to the ground I Liquid Rain or drizzle a lt05mm a l I Ice Hail or rau el lt5 E m 3 mm r E I Ice crystals Snow 3 r g D n I Depth Is In mm ofllquld E 3 water i e melt snow or dcwymmi mmme hail vmdnlgm a a m mm a n m rmdlugM Tlme 182008 Coding of Winds Review B Wind Speed Wmd Dwrecuon mnu dwacmm Thu mum hum wmen wwmd s Mowmg An Example Wind and Pressure on the Synoptic Scale measurement metMmquot ANACdeIu W6 EmgenemW m or Memxi eorSmiHer Summary Temperature 7 Cunthed bysun andsezsun e 65 Ckm 2pserztenTrupusphere Pressure 7 Wewght ersrrsbeve e Decreasesupwzrd Mm39sture a Humidity 7 Saturatmn and re ztwe humwdwty e Cundensesmtuduudsrrrewewtypes e preerprtstrenrsusrrem duudstugmundrrrewewtypes wrnd Ended an maps with ags fur every 10 kt m be ence with pressure fur Synaptic and Pweneteryeseewe Haws FOR NEXT TIME Do Problem lon P 17 Due Wednesdaythe 16 quot Read chapterz Surface Contrasts that Force Circulations by Heating amp Cooling Landwater Terrain elevations Pavednatural Soil moisture gradients Snowcover boundaries Cloud shadowing boundaries Ground albedo or vegetation gradients Nighttime Land Breeze Sea Breeze Near Hatteras 1615L Sea Breeze N ear Hatteras 1645L Coriolis Force Causes the Sea Breeze to Veerin the Northern Hemisphere Marked by cooling and moistening Wind veers and strengthens Generally becomes gustier as wel Florida Sea Breeze in SE Flow Florida Sea Breeze in SW Flow Nurmal summertime prevailing Winds Dispiaees searbreeze eurivergeriee tn West coast Accuunts mr meire ram and lightning there o Interrupts SE ow 5 middlelatitude trough goes by Displaces sea breeze c nvection 0 east coast Convection often begins inland about rten a break eir weakness eippeisite Lake Okeechubee E n the day euriveetiem ean prupagate eastward aereiss the lades Propagates over the Everg shoreline in earlymid Southerly or SSE Flow Along Peninsula Furrns buth East and Westeceast Sea Breeze liriE s Clear lane uverthe center er the Peninsula Un ess there is a lutuf instability cunvectiun lS generally Weaker v Often cuncentrated near the end ufthe Peninsula PreExisting Shear and CAPE Cunvectiun prupagates upwind aeress the Peninsula initiated at uutfluvv buundaries Offshure cunvectiun at sunrise can be a eiue New eenvemen enen dies nut near the share lri late afternuun Anvil ean shield trurn sular heating Lagoon Breezes FrenanrigateSnaals Kureieene Sun Wems mirawm 4 u m deem lagoon v eter Orographic Convection Nocturnal Valley Flows Urban Heat Islands Land surface contrast between developed and open coun e Larger heat capacity Most pronounced with clear sky and light winds Warmer with lower visibility and sometimes are rain Heat and turbulence can break up inversions Sea Breeze Impacts Rain often comes right at rush hour Sinking motion and calm winds at night affect air quality Overcast can reduce electric power deman Some urban or flash flooding usually with synopticscale forcing For valley winds can contribute to local freezing conditions FOR NEXT TIME Read Chapter 11 Freezing Precipitation and Ice Storms pp 192206 282008 Lecture 1 Severe weather Large damaging hail 20 mm or 3A in Damaging winds 50 kt or 25 m 5391 Tornado or all of the above Scales of motion 7 Planetary st synoptic balanced gt 2000 km 7 MesnscaIe nnnhalanced 20002 km 7 Convective buoyant motions 505 km scale height 7 MicmscaIe near surlace lt 1 km Lecture 2 Lectures 3 8t 4 39 Surface observations of weather elements and Sky conditionsw Temperature ASOSrrreveryhour controlled by Sun and Season Upperrair observations Rawinsondes at DDZ and 122 TPH 8t Wind V into the lower stratos here ean 15Dc at surface with 55Dc km 1 lapse rate m Troposphere 7 S EWVTVLDEPWEE ZH shuwsmm as a function d P 39 Pressure Rad Microwave reflection from rain WEiEN 0 air above 7 LR relationship converts reflectivity to rainfall rate Decreases upward 7 Dopplerradar usesfrequency shift to compute wind component Molsmre amp Humldlw toward or away from the radar Saturation and relative humidity S te39mes Condenses into cloudsmreview types 7 Geostationary overafixedspotonthe equator eview types 7 Polaror ite onlooksa d y 7 Visible Light Infra Red and WaterVapor lma e 39 W 5C ded 0 maps W mf ags for eve 10 k Pro lers Special Doppler radars that take hourly wind soundings 39 In balance W39lth Pressure fOFSVHOPt39lC and PlanetarvScale utomated observations from ommercialaircraft 0W5 Lightning location network triangulates cloudrtorground strokes Precipitation rallsrrom clouds to groun Lecture 5 Lines of constant erm Upper air charts use height at constant pressure rather than pressure at constant height Usefui uppercair levels r 350 mb 15 kmlaclouds moisture snow or not a 500 mb 55 km cyclone motion et streams cyclones severe weather tormatlon a Tendency ror air to rotate around a vertical axis a Concentrated in circular storms and shear zones a Key to understnding complicated weather a quotVorticity m eterquot Review and be abie to interpret surface station rrlodeis on weather maps 282008 Forecast Process Surface Observatlurls Sateiilte images n EASTER mature E petition vi Guessvvurk 39 lx 39 1 Numerical Furecas tfur NOW 1 r oblectiveAnl is H l Stirlltlailzatlurl 39 Lecture 6 ForecastingaaPrediction of future atmospheric conditions F Dissemination Ill Global regional amp Local Boundary conditions needed around the edge Forecast duration s short lt 3 days Medium 3E7 days wee ks Numerical Model Details Governing Partiai Differentiai Equations Einite difference represe ation Extrapoiate forward into the future CFL Criterion D DXlt C Higher resolution improves forecast 39 Dome Ensembles chaos and spaghetti diagrams Humans can generally improve on model output orecast process Observation Initialization Simulation St But Takes more grid points and more time steps because of CFL Lecture 7 Unstabie Neutral ls Metastab e Archimedes Principai oblects less dense than their surroundings rise buoyantly and convesel Lapse Rate The decrease of temperature with heightharrles in environmetal and Parcel avors Adioboa39o Praness No heat added or removed a D Wurkbaiarlces temperature change Mo st Wurk bala ces temperature and vapor mixingratio change iii 7 i stab tydepends upon environmental lapse r te Absuiute stab R b in rrlul39 d dryadl39abats Absuiute irl to e to r 3 m So 639 e to Parce dyn c m s adiabatically lbutnotbuoyantlyl to LFC then buoyantly to Et which corresponds to cloud top because the parcel is not buoyant bove iiftirlg or heating toget to tEc RisingParcellz i Thermodyna mics55 gap Lecture 8 instability tavors convection in the troposphere s o Diagram More unstable ror warm moist at the surrace and cool alort Parcei ascerl 7 Air rises dry adiabatically with constant o to LCL Cooler than environment to LFC T nbuoyantuntilitreachesEt stability indices 7 tlashowalter TlenvirlaTloartellatsoorno e rlaorTlSool cr rolaulanSoolnr vri cr 7 K index complicated tomoination otr a TD PE lacllvl Energy available troni toniection la ene39EV investment to start convection 282008 Geostrophic Balance L A pressure gradient force 5340 m i a 5mm 4 geastropmc wlnr Coriolis Force 5450 m Canahs anu per rust haiance eaun mnev Mastamman arrangememimiavgerscaie Immaspnevm nurans Lecture 9 Forces Pressure Gradie f Corioiisv Frictio r quotCentrifugaiquot Geostrppnrc baiance between PGF amp cp Friction causes crossrisobar ow to iow pressure Hydrostatic baianceNerticai pressure gradient baiancesgravity Thermai wrnd Hpn39zontar ternperature gradients iead to increasing nergntgradrents aioft and snear pr geostrpnrcwrnd Strong temperature gradients aiong surrace amp upper fronts causejetstrearns Vorticity Stretching We arsrnpunan atwrntrms sretcneu vem iiv stretcnrngatpranetarywrna erm i matmn rs rnarn Saurue My mtyr tneatmaspnere Varnatysqursnngwarmne mnerwav Frrmanrstnemarnsrnka wrnatyrarangwrtnvmex sqursnmz nunaenmnnmeuurnsuraeueaner Jetstreaks Mm nare srawmnan ne wrnu sa tnat navessnraucn ne pattern reamnan WeH de ned 4 quadrant pattern a ascent and descent n rgn and er a e at n tn and ght aeeanesnaremnpumeur snenmsmneu uarnernrssneaanrnamaepr uemrearseamurransu evennerarnanan How Does All of This Cause Storms m Ma Wau laud um rmrnau r quot 39 em Lecture 10 Drnes Carnpensatran Dwergence above convergence and convergence above dwergen ce pgeastrapnrcnpw rn Jetstrezks cuntmis upper pruengence and convergence Aueuslm nrc uwsduetucwvztumacceierztmnrfndmn raurquaprantrna 2 e upper divergence and nsrng matan rn ngnt entrance and ie em e upper tamergenue and sinking matan rn ie entrance and Hgnt em a Vdanrtturvature raduuesmme enuernentranueanddwtrgente rnexrt and tanver erytaranneveranremrv ure Vumuty mudei pr arrnawrng tnraugn a j arezk prpnpes a cancrse expiznztmn at upper convergence and prvergence Superpasrtran ufzjetstrezk mera surfacefmntzi zanerstne rnecnanrsrn furfurmztmn pr frantzi cyci an es 282008 Formation of Occluded Fronts B Lecture 11 AvMasses aomes oranwnn weu7uenneu Empemture and humldlw uenveurmm a sourte region Fronts aounuanes between avmasses Kind ornonx mom orWarm is nemneu bvthetemperature Mme alrthat anwes wnn Coldfrontsarestewerandmovefasterthanwarmfroms SKanonahFrom FlowismosKlvparallelwiththefront SKabiliwofwarmavtoSampEz volsramfall 7 Unstable mnvemnnmwarmair 7 stable Stratifnrm rain llsthrwghfrnmal Mme We Did an DNlme Surfaze humldlw boundaW erFronK Boundaw between using moist tom avamp and Sinking umsomewnauomenan Duludedant ColdfromLauhesuntowarmhontwedgmga laverofmoistavupward 5 Where Do US Frontal Cyclones Form Weather Patterns Lee ofthe Rocky Mountains if 7 Alberta 3391quot 7 Colorado Wyoming New Mexico A Gulf Coast 9 Carolinas Coast Lecture 12 Open Wave With Merging Jet cycunes e m vev e enca e Va vupma v teemnenaees Streaks Gulvcaasl Oven Gulvsl Lee Cycl g nesis Amlwdamc awavev mm o E Whenthe uppev quotam isahead EJDHhe dwhne theve e en invev a canve mndependsupaninsisbihlvmv arm awandsl nglhmlhe Mav on one nne at mm nnes at u e mi emu smng convection UppevFvunl m Culd anl catches up Wilhlhe Wavm nenl mlhe unclusmn pmeess 7 Apuul e1 m amssqueezedupwavd belwe the ms 7 cmeanl anovvannrmnl unclusmn types depending upun Wuh e lhevlhe culdes1 an is behind my ahead enne sunaee Lecture 13 282008 Gulf coast and offshore sources Coastal and Ohio Valley storm tracks A single Jet Streak can ca use significant snowfall but Nor easters are intense because of Contrast between land an se Merging Jet Streaks from PolarFront and Subtropical Jets Sea is a source of latent and sensible heat Cold air damming and onshore flow ca use heavy snow FOR NEXTTIME Exam on Wednesday 13 February 08 For Friday 15 February Local Winds No reading assignment just notes posted
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