Weather 14th Annual Hot Air Balloon Safety Seminar

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Weather 14th Annual Hot Air Balloon Safety Seminar. Rick Davis Senior Meteorologist National Weather Service - Tampa Bay Area. Observing the Weather. ASOS - Automated Surface Observing System. Wind Direction and Speed. Pressure measured at the Tower or other location nearby. - PowerPoint PPT Presentation

Text of Weather 14th Annual Hot Air Balloon Safety Seminar

  • Weather14th Annual Hot Air Balloon Safety SeminarRick DavisSenior MeteorologistNational Weather Service - Tampa Bay Area

  • Observing the WeatherASOS - Automated Surface Observing SystemRainTemp & Dew PointPrecip type and intensityWind Direction and SpeedData UnitVisibilityPressure measured at the Tower or other location nearby.

  • ASOSFacts and Figures569 FAA sponsored sites313 NWS sponsored sitesProvides nonstop weather info, updating every minute if neededComputer generated voice broadcasts gives pilots updates critical to safe landingsUsing FAA VHF ground-to-air radio or appended to ATIS broadcastInformation is also available through the phone or on the internet

  • AWOSAutomated Weather Observing SystemAWOSs cost about $94,000 and are much less expensive than ASOSsWho owns themFederal AWOSs are maintained by the FAAMost AWOSs are owned and maintained by states, airports, or other local interestThere are three main types of AWOSsAWOS I - temp, dew point, pressure, wind, density altitudeAWOS II - adds visibilityAWOS III - adds cloud informationAWOS IIIp - adds precipitation type sensor

  • ASOS/AWOS LocationsFlorida

  • Decoding METARsWinter ObservationsMETAR KTPA 101955Z 33015G22KT 1/2SM FG VV002 19/19 A2955 RMK A02 PK WND 32035/1915 TWR VIS 3/4 SLP028 P0004 T01920188RemarksAutomated precipitation reportingPeak wind northwest at 35kts at 1915ZTower visibility 3/4 mileSea level pressure 1002.8 MB00.04" rain in last hourTemp = 19.2 CDew = 18.8 C

  • Aviation ForecastsTafs/TwebsFrom NWS in RuskinKFMYKRSW

  • Decoding TAF ForecastsSome InsightsTAF AMDKFMY 141542Z 141612 33030G40KT 2SM RA B KN010 TEMPO 1618 32035G44KT 3/4SM +TSRA SQ BKN008 OVC015CB FM1800 32025G32KT P6SM BKN020 TEMPO 1821 ....- Most detail is in first 12 hours, generalized outlook after 12 hours- Issued four times a day at 06Z, 12Z, 18Z, and 00Z- Format of each forecast group is wind, weather, clouds- Naming of present weather has a strong French influence- GR is hail >1/4 inch- GS is hail < 1/4 inch- FU is smoke

  • Weather BalloonsThe RadiosondeLaunched at the same time across the world (11Z & 23Z)Rises 1000 feet per minuteReaches 90,000 ft in 1.5 hoursBalloon expands to 35 feet before explodingMeasures:TemperatureDew PointWind direction and speedPressure

  • Radiosonde DataStation Map and Data Plot

  • Doppler Radar

  • Doppler VAD Wind ProfilesVelocity Azimuth Display

  • General Winds

    Large-scale winds caused by the pressure patterns associated with high and low pressure areas.

  • Fronts & InstabilityIR satellite image overlaid with radar and fronts

  • Wind Flow Associated With Pressure Systems and Fronts

    Wind direction ahead of an approaching low pressure system and cold front will generally be southerly. Wind Speed will normally increase ahead of approaching systems.

    Wind direction behind a cold front and low pressure system will become northerly. Wind speed will normally be stronger just behind the front, then will slowly decrease.

  • Sources of LiftFronts and Low Pressure SystemsLH80s70s60sCold air weighs more than warm air

  • Local Winds

    Smaller-scale winds caused by local temperature differences.

  • Seabreezes

    During a clear day. . . sunshine heats the land to a greater extent than the water.

    Warm air over the land rises and is replaced by cooler, moister, marine air.

  • Sea Breezes (contd)An area experiencing a sea breeze will see:A temperature decrease 5-7o F.An RH increase of 10-15 %.A possible change in wind speed and direction.Thunderstorms in unstable air.

  • cumulus cloud thatmay form due to rising air reaching dewpointBubble ofWarm AirLocalized ThermalsCooler SinkingAir

  • Air MotionStability = Vertical MotionWind = Horizontal Motion

  • Wind ShearTwo Types of Wind Shear

    Directional Shear - Wind direction varies with height.

    Speed Shear Wind speed significantly increases with height.


  • InstabilityParcel TheoryA parcel is a small bag of air (size of cubic foot)Acts like a hot air balloonDoesnt let air in or outThe bag will rise if it is warmer than the surrounding airThe bag will sink if it is colder than the surrounding air

  • Parcel TheoryParcels act like bags of air50 at 10,000 ft

    70 at 5000 ft

    90 at surfaceAIr

    Temperature7070Will this parcel rise or sink?The parcel will rise because the air inside the parcel > air outside(70 > 60)Will this parcel rise or sink?The parcel will sink because the air inside the parcel < air outside(70 < 80)

  • InstabilityRelating to Temperature Inversions50




    90Surface10,000 feetStable Layer8292What happens when temperatures warm with height?(a temperature inversion)

  • InstabilitySea Breeze and Outflow Boundaries50





    90Surface10,000 feetStable Layer72829250



    886355Sea BreezeNeed lifting mechanism to get parcel above inversion

  • Unstable Atmosphere

  • Stable Atmosphere

  • Unstable, But No Storms?Why is that?Need additional lift to get thunderstorms to developStable Layer

  • Atmospheric StabilityStability is a measure of the equilibrium of the atmosphere to vertical motion.

    Stable Air - Resists Vertical Motion

    Unstable Air - Encourages Vertical Motion

  • Stability ContinuedParamount to the concept of stability is:

    Relative to the surrounding environment: hot air rises and cold air sinks.

  • Remember that indicators of stable and unstable atmospheres are instantaneous indicators. Changes in stability can be extremely rapid.

  • Stability is a function of the Lapse Rate

    Change in temperature with height

  • Average Lapse RateDecrease of 3.5 degrees F per1000 feet of altitudeHT70o1,00066.6o

  • Lapse Rate and StabilityIf the measured lapse rate is greater than 5.5 F per 1000 ft, the atmosphere is unstable.If the measured lapse rate is less than 5.5 F per 1000 ft, the atmosphere is stable.If the measured lapse rate is equal to 5.5 F per 1000 ft, the atmosphere is neutral.

  • InversionsLayer of air in which the temperature rises with height.

    3 TypesRadiation or Nighttime Inversion

    Marine Inversion


  • Temperature Inversions

    As you go aloft, temperature normally decreases at a rate of 5.5 F. per 1000 feet.

    Temperature inversion occurs when the temperature increases with height instead of decreasing.

  • Temperature InversionsTemperatureDewpoint

  • InversionsInversions normally dissipate as the surface temperature rises and mixing of the atmosphere begins, unless inversion is strong.

    Inversions frequently occur near the center of high pressure systems where winds are light and skies are clear.

  • Mixing HeightThe height below which relatively vigorous mixing in the atmosphere is taking place

    Winter Daytime 2- 4 Thousand FeetSummer Daytime 4-6 Thousand Feet

    Nighttime/early morning 100-500 feet when stable to 1000 feet in unstable

  • Transport WindsAverage horizontal wind speed and direction between the surface and the mixing height.Determines the rate of horizontal movement.

  • Dispersion IndexA forecast tool used to estimate daytime and nighttime stability.Incorporates the stability, transport winds and mixing heights.Daytime DI: 50-75 = unstableNighttime DI: 1-4 = stable

  • ThunderstormsThunderstorms significantly effect the local environmentGusty erratic windsCooler temps/Higher RHRain - Possible Hail/TornadoesLightning as far as 10 miles from the storm

  • Safety Above All ElseLightning Safety#1 Florida weather killerAverage 10 fatalities and 40 injuries each yearCan strike over 10 miles away from the storm

  • When is Lightning Most Dangerous?June through September

  • NOAA Weather RadioAutomated All-Hazards Warning InformationWarns of natural and man made hazardsAlerts you even when youre sleepingNew radios can be programmed just for your county

  • Visit Us on the Web!

  • Local NWS Office

  • Aviation Weather Centerhttp://aviationweather.govAIRMETs, SIGMETs, SIGWX Progs, etc.Aviation Digital Data ServiceStandard unofficial briefingExperimental productsTraining

  • Useful Web -- National Weather Service, Tampa Bay, Florida -- National Weather Service, Southern Region Headquarters, Ft. Worth, TX -- Aviation Weather Center, Kansas City, Missouri -- National Weather Service Headquarters, Washington, D.C. Storm Prediction Center, Norman, OK


  • THE END! Norman, OK 06/28/99 (Todd Lindley)