This homework assignment focuses on vital concepts from Chapter 5 related to moisture, cloud formation, and precipitation. Pilots are required to read Chapters 5 and 7 and complete the AOPA’s Weather Wise Ceiling and Visibility course by Thursday. Understanding these elements is crucial for safe flying, as they directly affect visibility, flight safety, and weather prediction. Ensure that your pilot records are accurate and complete the necessary documentation for any discrepancies as outlined in the AOPA resources.
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Understanding Moisture, Cloud Formation, and Precipitation in Aviation Weather
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CHAPTER 5 MOISTURE, CLOUD FORMATION AND PRECIPITATION
Matching pilot record not found. Back to DUAT.com Registration Your Pilot Name and Certification Number are not in our database. Please check the last name and number on your pilot certificate. These must match our FAA records exactly to issue a DUAT Access Code. If you recently received your certificate, our records may still have you listed under your student medical number. Try entering your student medical number (including the first two letters!). If you are unsuccessful in obtaining an access code on-line, your pilot information is probably not contained in the FAA supplied Airman File Database. Please contact our 24-hour help desk at 1-800-243-3828. The FAA requires us to obtain a copy of the following documentation to add you into the system. If you are in one of the following Categories, Email, FAX or Mail the following information to DTC (please include your daytime phone number in case we should need to contact you): Pilots: Send a copy of your Pilot and Medical Certificates. Student Pilots: Send a copy of your Student Pilot (Medical). Glider & Balloon Pilots: Send a copy of your Pilot Certificate (With rating).Flight Instructors: Send a copy of your Pilot Certificate (With rating).Aviation Ground Instructors: Send a copy of your Pilot Certificate (With rating).Ultra-Light Pilots: Send a copy of your United States Ultra-light Association Membership Card.Dispatchers: Send a copy of your Dispatcher Certificate or call our Help Desk for information at: 1-800-243-3828. Sport Pilots:Requires either a pilot certificate, sport pilot certificate or student sport certificate and either a 3rd class FAA medical certificate or a valid U.S driver's license as evidence of medical eligibility (provided the individual's most recent application for an FAA medical certificate was not denied, revoked, suspended or withdrawn). Please click on the FAA Certificates link for more information about Sport Pilot certificates. DTC Email:request@dtcduat.comDTC Help Desk:1-800-243-3828DTC FAX Number:1-888-445-3828DTC Address:Data Transformation Corp. 108-F Greentree Road Turnersville, NJ 08012 Once received, your information will be added to the DTC DUAT Pilot database and we will assign you an Access Code/Password. You will receive a confirmation email if an email has been provided or in the event you only supplied a phone number, the Help Desk will call you with your security codes. If you do not receive an email or a call from DTC, please call our 24 hour Help Desk to obtain your security codes at 1-800-243-3828. Other Users:Other organizations who believe they have a legitimate reason for using the DUAT service should write, Phone, FAX, or E-mail their request to:Matoka Forbes (DUATS COTR) (202) 385-7665Flight Services Program Management, AJR-B21 matoka.forbes@faa.gov1575 I Street, Suite 9120 NW Matoka ForbesWashington, DC 20005 ATO-R DUATS COTR
WINTER STORM WARNINGin effect until Thursday, Jan 19, 4:00 PM ...WINTER STORM WARNING REMAINS IN EFFECT FROM 4 AM WEDNESDAY TO 4 PM PST THURSDAY... A WINTER STORM WARNING REMAINS IN EFFECT FROM 4 AM WEDNESDAY TO 4 PM PST THURSDAY. * SNOW ACCUMULATIONS: FOR THE UPPER COLUMBIA BASIN...THE WATERVILLE PLATEAU...THE WENATCHEE AREA...AND THE LEWISTON AREA...SNOW AMOUNTS OF 4 TO 7 INCHES WILL BE COMMON BY THURSDAY. * TIMING: HEAVY SNOW IS EXPECTED WEDNESDAY INTO THURSDAY. * LOCATIONS INCLUDE: MOSES LAKE...EPHRATA...OTHELLO...QUINCY... RITZVILLE...GRAND COULEE... ODESSA...WILBUR...COULEE CITY... WENATCHEE... CHELAN... ENTIAT... CASHMERE...WATERVILLE... MANSFIELD... BADGER MOUNTAIN ROAD PRECAUTIONARY/PREPAREDNESS ACTIONS... A WINTER STORM WARNING MEANS SIGNIFICANT AMOUNTS OF SNOW ARE EXPECTED OR OCCURRING. STRONG WINDS ARE ALSO POSSIBLE. THIS WILL MAKE TRAVEL VERY HAZARDOUS OR IMPOSSIBLE.
Plan for the Weather • You have control over most of the factors involved with flying, but you have no control over the weather. Good weather or bad weather, you must adapt your flying to it.
WHO IS BRAVE ENOUGH TO TRY? • KMWH 131152Z AUTO 31003KT 5SM -FZRA BR BKN011 OVC017 M01/M01 A3002 RMK AO2 SLP180 P0004 60008 70010 T10061011 11006 21050 58013 • Hopefully no one!!! –FZRA is a no go for most aircraft especially light training aircraft
KMWH 131152Z AUTO 31003KT 5SM -FZRA BR BKN011 OVC017 M01/M01 A3002 RMK AO2 SLP180 P0004 60008 70010 T10061011 11006 21050 58013 • Light freezing rain • P0004= hourly precip amount 4/100 of an inch precip. • 60008= .8 inches in last 6 hours can also be 3 hours • 70010=24 hour precip amount included in 12 UTC =1 inch in last 24 hours • T10061011=Temp -6.1 C / DPT -1.1 C • 11006= 6 hour max temp = -.6 C • 21050= 6 hour minimum temp = -5 C • 58013 = 3 hour pressure tendency = 8 is the character of pressure change (need chart = atmospheric pressure now lower than 3 hours ago. Steady or increasing, then decreasing; or decreasing then decreasing more rapidly) with a change of 1.3 hectopascals • Federal Meteorological Handbook No. 1 section 12 (search FMH-1) • http://www.ofcm.gov/fmh-1/pdf/L-CH12.pdf
CLOUDS & PRECIP. • Clouds and precipitation can obscure surface features and other aircraft. They can envelope high ground and may be associated with severe turbulence and ice formation. • Clouds form when water vapour gas condenses into liquid water droplets or sublimates into ice crystals
WATER VAPOR • Water Vapor is invisible just as oxygen.
WATER VAPOR • Two commonly used terms to express the amount of water vapor in the air are • Relative Humidity and • Specific Humidity.
DEFINITIONS • Relative Humidity = expressed as a % of actual water vapor present to that which could be present • If a given volume of air is cooled to some specific temp., it can hold no more water vapor than is actually present, relative humidity becomes 100% or saturated
DEFINITIONS • Specific Humidity =The ratio, by weight, of the water vapor in a sample of air to the combined weight of the water vapor and the dry air.
Type of Clouds/Precip. • The extent and type of cloud and precipitation produced will depend on the amount of water vapour available, the abundance of nuclei, stability of the air and the amount of cooling that the air undergoes.
DEFINITIONS • Dew Point Temperature = is the temperature to which air must be cooled to become saturated. • The higher the temp the more moisture it can hold • So, for the air to become saturated, either • 1. Cool the Temp, 2. Raise the Humidity
FOG • Temp/Dew Point Temp spread is 2ºC (4 ºF) and narrowing condensation/ fog/low clouds should be expected. • Water vapor must condense for fog to form. If there are no condensation nuclei present then even with 100% relative humidity, fog will not form. • Salt, dust combustion by products, smoke are all classified as condensation nuclei
FOG • Fog is a surface based cloud composed of either water droplets or ice crystals. • Less than 5/8 S.M. vis = FG • 5/8 S.M. or more = BR • With the right conditions fog can form very quickly (few minutes) VFR-IFR. • Be very cautious flying when the temp/ D.P.T. spread is close and getting closer. • Fog or a cloud may form: by cooling air to its dew point, by adding moisture to the air or condensation nuclei.
FOG • Several different types of fog: • Radiation Fog = Fog that forms on a clear calm night or day break when the surface of the earth is cooled by radiation until the temperature of the air near the the surface is below its initial dew point temp. Restricted to land because water surfaces cool little from nighttime radiation. Usually burns off rapidly after sunrise.
FOG • Advection Fog = forms when moist air moves over colder ground or water. Common along coastal areas. At sea it is called sea fog.
FOG • Upslope fog = forms as a result of moist, stable air being cooled adiabatically as it moves up sloping terrain. (as air rises it cools) • Precipitation-induced fog - forms when relatively warm rain or drizzle falls through cool air, and evaporation from the precip saturates the cool air.
FOG • Ice Fog = cold weather when the temp is below freezing and water vapor sublimates directly as ice crystals. Can be blinding flying into the sun. • Fog on a METAR is used to indicate visibility of less than 5/8 of a SM
CHANGE OF STATE • Sublimation - ice to vapor, vapor to ice • Evaporation - water to vapor • Condensation - vapor to water • Freezing -water to solid water • Melting - solid water (ice) to water • Virga - precipitation that never reaches the ground • Virga is a perfect example of condensation then evaporation
CHANGE OF STATE • Evaporation, condensation, freezing, melting, and sublimation are changes of state in water. The exchange of heat energy is required to change a substance from one state to another.
CHANGE OF STATE • The exchange of heat energy when a substance changes from one state to another is called latent (hidden) heat. • Latent heat of vaporization - when water changes to vapor it takes heat from the surrounding environment (hidden in the water vapor. • Like when you sweat it cools your body heat is taken
CHANGE OF STATE • Latent heat of fusion - when water changes to ice, it gives off heat to the surrounding environment • Like when farmers use water to keep crops or fruit from freezing. • Latent heat of condensation - when the water vapor condenses back into liquid water, this energy is released to the atmosphere. Thus condensation is a warming process.
SUPER COOLED WATER • Water droplets can exist below 32º F. We find them aloft between 0º C and -15º C. They may exist at temps lower than -15º C. They have been known to exist up to -40º C • Freezing is complex, and liquid water droplets often condense or persist at temperatures colder than 0º C because the molecular motion of the droplet remains large enough to weaken any formation of an ice crystal within the droplet . Striking an aircraft causes immediate freezing on impact.
DEW AND FROST • If the temp of a surface cools below the dew point, dew will form on that surface • Frost happens when the dew point is below freezing and the surface is colder than freezing
CLOUD FORMATION • Normally, air must become saturated for condensation or sublimation to occur. • The major cooling mechanism that causes condensation is adiabatic expansion. There are 5 processes which result in the ascent of air and adiabatic cooling and they are: • 1. Convection, 2. Mechanical turbulence, 3. Frontal lift, 4. Orographic lift, and 5. Convergence.
CLOUD FORMATION • Two other causes of cooling are, the evaporation of rain falling from higher cloud (rain partially evaporates as it falls through the air. The heat required for evaporation is taken from the air through which the rain is falling thus cooling the air • and with advection the movement of air over a surface colder than the air
#1. CLOUDS FORMED BY CONVECTION • Convection consistes of air rising rapidly in shafts or bubbles and it occurs in unstable air. A layer of air can be made unstable when it is heated from below either by moving over a portion of the earth’s surface warmer than itself or by the earth’s surface being heated by the sun.
CONVECTION CLOUD BASES • Same water vapor content, with an increase in temperature cloud bases rise (DALR 3 degrees per/1000ft)
ESTIMATING CUMULIFORM CLOUD BASES Pg. 51 • You can estimate height of cumuliform cloud bases using surface temperature-dew point spread. Unsaturated air in a convective current cools at about 3 degrees per 1000 feet; dew point decreases at about 1F or 5/9 degree C per 1000ft. Thus, in a convective current, temperature and dew point converge at about 2.5C per 1000/ft
ESTIMATING CUMULIFORM CLOUD BASES Pg. 51 • You can get a quick estimate of a convective cloud base in thousands of feet by rounding these values and dividing into the spread or by multiplying the spread by their reciprocals. When using Fahrenheit, divide by 4 or multiply by .25; when using Celsius, divide by 2.2 or multiply by .45
QUESTION • If the surface air temperature is 35 degrees C and the dew point is 26 degrees C. (assume standard lapse rates for a cumiliform cloud)what is the cloud base. • 9 degree spread/2.2 =4.0909 • *1000 = 4100 feet. • Read page 51!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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