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
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 VAD Wind ProfilesVelocity Azimuth Display
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
Smaller-scale winds caused by local temperature differences.
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.
BOTH ARE IMPORTANT TO AVIATION!!!
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, 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
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.
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!http://weather.gov
Local NWS Office
Aviation Weather Centerhttp://aviationweather.govAIRMETs, SIGMETs, SIGWX Progs, etc.Aviation Digital Data ServiceStandard unofficial briefingExperimental productsTraining
Useful Web Siteswww.srh.noaa.gov/tbw -- National Weather Service, Tampa Bay, Florida
www.srh.noaa.gov -- National Weather Service, Southern Region Headquarters, Ft. Worth, TX
www.aviationweather.gov -- Aviation Weather Center, Kansas City, Missouri
www.weather.gov -- National Weather Service Headquarters, Washington, D.C.
www.spc.noaa.gov Storm Prediction Center, Norman, OK
QUESTIONS AND/OR COMMENTS???
THE END! Norman, OK 06/28/99 (Todd Lindley)