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 Rain Temp & Dew Point Precip type and intensity Wind Direction and Speed Data Unit Visibility Pressure measured at the Tower or other location nearby.

ASOS Facts and Figures ▪569 FAA sponsored sites ▪313 NWS sponsored sites ▪Provides nonstop weather info, updating every minute if needed ▪Computer generated voice broadcasts gives pilots updates critical to safe landings ▸ Using FAA VHF ground-to-air radio or appended to ATIS broadcast ▪Information is also available through the phone or on the internet

AWOS Automated Weather Observing System ▪AWOSs cost about $94,000 and are much less expensive than ASOSs ▪Who owns them ▸ Federal AWOSs are maintained by the FAA ▸ Most AWOSs are owned and maintained by states, airports, or other local interest ▪There are three main types of AWOSs ▸ AWOS I - temp, dew point, pressure, wind, density altitude ▸ AWOS II - adds visibility ▸ AWOS III - adds cloud information –AWOS IIIp - adds precipitation type sensor

ASOS/AWOS Locations Florida

Decoding METARs Winter Observations METAR KTPA Z 33015G22KT 1/2SM FG VV002 19/19 A2955 RMK A02 PK WND 32035/1915 TWR VIS 3/4 SLP028 P0004 T Remarks Automated precipitation reporting Peak wind northwest at 35kts at 1915Z Tower visibility 3/4 mile Sea level pressure MB 00.04" rain in last hour Temp = 19.2 C Dew = 18.8 C

Aviation Forecasts Tafs/Twebs From NWS in Ruskin KFMY KRSW

Decoding TAF Forecasts Some Insights TAF AMD KFMY Z G40KT 2SM RA B KN010 TEMPO G44KT 3/4SM +TSRA SQ BKN008 OVC015CB FM G32KT P6SM BKN020 TEMPO 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 Balloons The Radiosonde ▪Launched at the same time across the world (11Z & 23Z) ▪Rises 1000 feet per minute ▪Reaches 90,000 ft in 1.5 hours ▪Balloon expands to 35 feet before exploding ▪Measures: ▸ Temperature ▸ Dew Point ▸ Wind direction and speed ▸ Pressure

Radiosonde Data Station Map and Data Plot

Doppler Radar

Doppler VAD Wind Profiles Velocity Azimuth Display

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

Fronts & Instability IR 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 Lift Fronts and Low Pressure Systems L H 80s 70s 60s Cold 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 (cont’d)  An area experiencing a sea breeze will see :  A temperature decrease 5-7 o F.  An RH increase of %.  A possible change in wind speed and direction.  Thunderstorms in unstable air.

cumulus cloud that may form due to rising air reaching dewpoint cumulus cloud that may form due to rising air reaching dewpoint Bubble of Warm Air Localized Thermals Cooler Sinking Air

Air Motion Stability = Vertical Motion Wind = Horizontal Motion

Wind Shear  Two Types of Wind Shear  Directional Shear - Wind direction varies with height.  Speed Shear – Wind speed significantly increases with height.  BOTH ARE IMPORTANT TO AVIATION!!!

Instability Parcel Theory ●A parcel is a small bag of air (size of cubic foot) ●Acts like a hot air balloon -Doesn’t let air in or out -The bag will rise if it is warmer than the surrounding air -The bag will sink if it is colder than the surrounding air

Parcel Theory Parcels act like bags of air 50 ̍ at 10,000 ft 70 ̍ at 5000 ft 90 ̍ at surface AIrTemperatureAIrTemperature 70 ̍̍ Will 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 ̍ )

Instability Relating to Temperature Inversions 50 ̍ 60 ̍ 85 ̍ 80 ̍ 90 ̍̍ Surface 10,000 feet Stable Layer 82 ̍̍ 92 ̍̍ What happens when temperatures warm with height? (a temperature inversion)

Instability Sea Breeze and Outflow Boundaries 50 ̍ 60 ̍ 70 ̍ 85 ̍ 80 ̍ 90 ̍̍ Surface 10,000 feet Stable Layer 72 ̍̍ 82 ̍̍ 92 ̍̍ 50 ̍ 60 ̍ 80 ̍ 88 ̍̍ 63 ̍̍ 55 ̍̍ Sea Breeze Need 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 develop Stable Layer

Atmospheric Stability  Stability is a measure of the equilibrium of the atmosphere to vertical motion.  Stable Air - Resists Vertical Motion  Unstable Air - Encourages Vertical Motion

Stability Continued  Paramount 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 Rate Decrease of 3.5 degrees F per 1000 feet of altitude H T 70 o 1,000’ 66.6 o

Lapse Rate and Stability If 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.

Inversions Layer of air in which the temperature rises with height. 3 Types Radiation or Nighttime Inversion Marine Inversion Subsidence

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 Inversions TemperatureDewpoint

Inversions  Inversions 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 Height  The height below which relatively vigorous mixing in the atmosphere is taking place  Winter Daytime 2- 4 Thousand Feet  Summer Daytime 4-6 Thousand Feet  Nighttime/early morning feet when stable to 1000 feet in unstable

Transport Winds  Average horizontal wind speed and direction between the surface and the mixing height.  Determines the rate of horizontal movement.

Dispersion Index  A forecast tool used to estimate daytime and nighttime stability.  Incorporates the stability, transport winds and mixing heights.  Daytime DI: = unstable  Nighttime DI: 1-4 = stable

Thunderstorms  Thunderstorms significantly effect the local environment  Gusty erratic winds  Cooler temps/Higher RH  Rain - Possible Hail/Tornadoes  Lightning as far as 10 miles from the storm

Safety Above All Else Lightning Safety ▪#1 Florida weather killer ▪Average 10 fatalities and 40 injuries each year ▪Can strike over 10 miles away from the storm

When is Lightning Most Dangerous? June through September

NOAA Weather Radio Automated All-Hazards Warning Information ▪Warns of natural and man made hazards ▪Alerts you even when you’re sleeping ▪New radios can be programmed just for your county

Visit Us on the Web!

Local NWS Office

Aviation Weather Center ▪AIRMETs, SIGMETs, SIGWX Progs, etc. ▪Aviation Digital Data Service ▪Standard unofficial briefing ▪Experimental products ▪Training

Useful Web Sites 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

QUESTIONS AND/OR COMMENTS???

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