Type of Precipitation Inter Nal NWS Code SYNOP Ww Tab.4677
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Winter Precipitation Liquid–Ice Phase Transitions Revealed with Polarimetric Radar and 2DVD Observations in Central Oklahoma
MAY 2017 B U K O V CICETAL. 1345 Winter Precipitation Liquid–Ice Phase Transitions Revealed with Polarimetric Radar and 2DVD Observations in Central Oklahoma PETAR BUKOVCIC ´ NOAA/National Severe Storms Laboratory, and Cooperative Institute for Mesoscale Meteorological Studies, and School of Meteorology, and Advanced Radar Research Center, University of Oklahoma, Norman, Oklahoma DUSAN ZRNIC´ NOAA/National Severe Storms Laboratory, Norman, Oklahoma GUIFU ZHANG School of Meteorology, and Advanced Radar Research Center, University of Oklahoma, Norman, Oklahoma (Manuscript received 30 June 2016, in final form 8 November 2016) ABSTRACT Observations and analysis of an ice–liquid phase precipitation event, collected with an S-band polarimetric KOUN radar and a two-dimensional video disdrometer (2DVD) in central Oklahoma on 20 January 2007, are presented. Using the disdrometer measurements, precipitation is classified either as ice pellets or rain/freezing rain. The disdrometer observations showed fast-falling and slow-falling particles of similar size. The vast majority (.99%) were fast falling with observed velocities close to those of raindrops with similar sizes. In contrast to the smaller particles (,1 mm in diameter), bigger ice pellets (.1.5 mm) were relatively easy to distinguish because their shapes differ from the raindrops. The ice pellets were challenging to detect by looking at conventional polarimetric radar data because of the localized and patchy nature of the ice phase and their occurrence close to the ground. Previously published findings referred to cases in which ice pellet areas were centered on the radar location and showed a ringlike structure of enhanced differential reflectivity ZDR and reduced copolar correlation coefficient rhv and horizontal reflectivity ZH in PPI images. -
Downloaded 10/01/21 08:52 PM UTC 186 WEATHER and FORECASTING VOLUME 16
FEBRUARY 2001 NOTES AND CORRESPONDENCE 185 Further Investigation of a Physically Based, Nondimensional Parameter for Discriminating between Locations of Freezing Rain and Ice Pellets ROBERT M. RAUBER,LARRY S. OLTHOFF, AND MOHAN K. RAMAMURTHY Department of Atmospheric Sciences, University of Illinois at Urbana±Champaign, Urbana, Illinois KENNETH E. KUNKEL Midwestern Climate Center, Illinois State Water Survey, Champaign, Illinois 9 December 1999 and 16 August 2000 ABSTRACT The general applicability of an isonomogram developed by Czys and coauthors to diagnose the position of the geographic boundary between freezing precipitation (freezing rain or freezing drizzle) and ice pellets (sleet or snow grains) was tested using a 25-yr sounding database consisting of 1051 soundings, 581 where stations were reporting freezing drizzle, 391 reporting freezing rain, and 79 reporting ice pellets. Of the 1051 soundings, only 306 clearly had an environmental temperature and moisture pro®le corresponding to that assumed for the isonomogram. This pro®le consisted of a three-layer atmosphere with 1) a cold cloud layer aloft that is a source of ice particles, 2) a midlevel layer where the temperature exceeds 08C and ice particles melt, and 3) a surface layer where T , 08C. The remaining soundings did not conform to the pro®le either because 1) the freezing precipitation was associated with the warm rain process or 2) the ice pellets formed due to riming rather than melting and refreezing. For soundings conforming to the pro®le, the isonomogram showed little diagnostic skill. Freezing rain or freezing drizzle occurred about 50% of the time that ice pellets were expected. -
News and Notes
346 BULLETIN AMERICAN METEOROLOGICAL SOCIETY NEWS AND NOTES Air Force Scientists Develop Technique The feasibility of dissipating supercooled clouds by for Cutting Holes in "Cold" Clouds seeding with dry-ice was recognized many years ago. Airborne equipment, previously developed to do this, A new technique for creating holes in supercooled cloud crushed large blocks of dry-ice into particles suitable for layers has been developed by Air Force Cambridge Re- seeding purposes. search Laboratories scientists. During recent flight tests This equipment had two particular limitations. First, using this technique, holes more than 3 miles wide were these machines produced about half powdered dry-ice created in supercooled clouds. which evaporated immediately upon dispersal from the Major James F. Church, project scientist in AFCRL's aircraft and was wasted. Second, the logistical problem Meteorological Research Laboratory is directing research of supplying enough dry-ice where needed and the high on the dissipation of supercooled stratiform clouds. The evaporational losses suffered during storage until used, program is under the technical management of the Air severely limited the utility of this technique. Force System Command's Electronic Systems Division. The Cloudbuster makes ice pellets by passing liquid The principal objective of this research is to provide C02 through an expansion nozzle and then compacting Air Force cargo and transport pilots with an economical the solid dry-ice powder, which is then formed, into proper capability to seed supercooled clouds with dry-ice pellets, size. The Cloudbuster has been designed with the capa- made on the aircraft and dispersed at will, to create bility of making different-sized pellets at the touch of a sizable holes in such cloud decks. -
METAR/SPECI Reporting Changes for Snow Pellets (GS) and Hail (GR)
U.S. DEPARTMENT OF TRANSPORTATION N JO 7900.11 NOTICE FEDERAL AVIATION ADMINISTRATION Effective Date: Air Traffic Organization Policy September 1, 2018 Cancellation Date: September 1, 2019 SUBJ: METAR/SPECI Reporting Changes for Snow Pellets (GS) and Hail (GR) 1. Purpose of this Notice. This Notice coincides with a revision to the Federal Meteorological Handbook (FMH-1) that was effective on November 30, 2017. The Office of the Federal Coordinator for Meteorological Services and Supporting Research (OFCM) approved the changes to the reporting requirements of small hail and snow pellets in weather observations (METAR/SPECI) to assist commercial operators in deicing operations. 2. Audience. This order applies to all FAA and FAA-contract weather observers, Limited Aviation Weather Reporting Stations (LAWRS) personnel, and Non-Federal Observation (NF- OBS) Program personnel. 3. Where can I Find This Notice? This order is available on the FAA Web site at http://faa.gov/air_traffic/publications and http://employees.faa.gov/tools_resources/orders_notices/. 4. Cancellation. This notice will be cancelled with the publication of the next available change to FAA Order 7900.5D. 5. Procedures/Responsibilities/Action. This Notice amends the following paragraphs and tables in FAA Order 7900.5. Table 3-2: Remarks Section of Observation Remarks Section of Observation Element Paragraph Brief Description METAR SPECI Volcanic eruptions must be reported whenever first noted. Pre-eruption activity must not be reported. (Use Volcanic Eruptions 14.20 X X PIREPs to report pre-eruption activity.) Encode volcanic eruptions as described in Chapter 14. Distribution: Electronic 1 Initiated By: AJT-2 09/01/2018 N JO 7900.11 Remarks Section of Observation Element Paragraph Brief Description METAR SPECI Whenever tornadoes, funnel clouds, or waterspouts begin, are in progress, end, or disappear from sight, the event should be described directly after the "RMK" element. -
The Mesoscale Dynamics of Freezing Rain Storms Over Eastern Canada
VOL. 56, NO.10 JOURNAL OF THE ATMOSPHERIC SCIENCES 15 MAY 1999 The Mesoscale Dynamics of Freezing Rain Storms over Eastern Canada K. K. SZETO Climate Processes and Earth Observation Division, Atmospheric Environment Service, Downsview, Ontario, Canada A. TREMBLAY Cloud Physics Research Division, Atmospheric Environment Service, Dorval, Quebec, Canada H. GUAN AND D. R. HUDAK Cloud Physics Research Division, Atmospheric Environment Service, Downsview, Ontario, Canada R. E. STEWART AND Z. CAO Climate Processes and Earth Observation Division, Atmospheric Environment Service, Downsview, Ontario, Canada (Manuscript received 2 June 1997, in ®nal form 9 June 1998) ABSTRACT A severe ice storm affected the east coast of Canada during the Canadian Atlantic Storms Project II. A hierarchy of cloud-resolving model simulations of this storm was performed with the objective of enhancing understanding of the cloud and mesoscale processes that affected the development of freezing rain events. The observed features of the system were reasonably well replicated in the high-resolution simulation. Diagnosis of the model results suggests that the change of surface characteristics from ocean to land when the surface warm front approaches Newfoundland disturbs the (quasi-) thermal wind balance near the frontal region. The cross-frontal circulation intensi®es in response to the thermal wind imbalance, which in turn leads to the development of an extensive above-freezing inversion layer in the model storm. Depending on the depth of the subfreezing layer below the inversion, the melted snow may refreeze within the subfreezing layer to form ice pellets or they may refreeze at the surface to form freezing rain. Such evolution of surface precipitation types in the model storm was reasonably well simulated in the model. -
ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere. -
Tornadoes Family Activity Sheets
A Tornado Is Born Page 1 of 3 Name ________________________________________________________________________ Step 1: Use books, the Internet and other resources to define each of the words below. If possible, draw a picture of the word to help others understand its meaning. anvil cloud: atmosphere: condense: cumulus cloud: cumulonimbus cloud: downdraft: front: funnel cloud: mesocyclone: supercell: thunderhead: updraft: vortex: vertical wind shear: A TORNADO IS BORN Visit the American Red Cross Web site Masters of Disaster® Tornadoes, Level 2 at www.redcross.org/disaster/masters Copyright 2007 The American National Red Cross A Tornado Is Born Page 2 of 3 Step 2: Below is a description of the way tornadoes form. Some of the words are missing. Use the words from Step 1 to complete the description. Then, draw a story- board on the back of the page showing the formation of a tornado. High in the _______________, cool air pushes against warm air. The place where the two kinds of air meet is called a ______. A front can stretch over 100 miles (161 kilo- meters). On warm days, the air near the ground is much warmer than it is at higher eleva- tions. Warm air rises by bubbling up from the ground, just like the bubbles in a pot of boiling water. If the air has enough moisture in it, the moisture ____________ and forms ____________________. Sometimes, the rising air is trapped by a layer of cooler air above it. As the day continues, the warm air builds up. If this pocket of warm air rises quickly, it can break through the cap of cooler air like water shooting up from a fountain and a __________________, or _________________ (kyu-mya-lo-NIM-buhs) cloud grows, topped by an ____________. -
Cloud Microphysics
Cloud microphysics Claudia Emde Meteorological Institute, LMU, Munich, Germany WS 2011/2012 Growth Precipitation Cloud modification Overview of cloud physics lecture Atmospheric thermodynamics gas laws, hydrostatic equation 1st law of thermodynamics moisture parameters adiabatic / pseudoadiabatic processes stability criteria / cloud formation Microphysics of warm clouds nucleation of water vapor by condensation growth of cloud droplets in warm clouds (condensation, fall speed of droplets, collection, coalescence) formation of rain, stochastical coalescence Microphysics of cold clouds homogeneous, heterogeneous, and contact nucleation concentration of ice particles in clouds crystal growth (from vapor phase, riming, aggregation) formation of precipitation, cloud modification Observation of cloud microphysical properties Parameterization of clouds in climate and NWP models Cloud microphysics December 15, 2011 2 / 30 Growth Precipitation Cloud modification Growth from the vapor phase in mixed-phase clouds mixed-phase cloud is dominated by super-cooled droplets air is close to saturated w.r.t. liquid water air is supersaturated w.r.t. ice Example ◦ T=-10 C, RHl ≈ 100%, RHi ≈ 110% ◦ T=-20 C, RHl ≈ 100%, RHi ≈ 121% )much greater supersaturations than in warm clouds In mixed-phase clouds, ice particles grow from vapor phase much more rapidly than droplets. Cloud microphysics December 15, 2011 3 / 30 Growth Precipitation Cloud modification Mass growth rate of an ice crystal diffusional growth of ice crystal similar to growth of droplet by condensation more complicated, mainly because ice crystals are not spherical )points of equal water vapor do not lie on a sphere centered on crystal dM = 4πCD (ρ (1) − ρ ) dt v vc Cloud microphysics December 15, 2011 4 / 30 P732951-Ch06.qxd 9/12/05 7:44 PM Page 240 240 Cloud Microphysics determined by the size and shape of the conductor. -
ICA Vol. 1 (1956 Edition)
·wMo o '-" I q Sb 10 c. v. i. J c.. A INTERNATIONAL CLOUD ATLAS Volume I WORLD METEOROLOGICAL ORGANIZATION 1956 c....._/ O,-/ - 1~ L ) I TABLE OF CONTENTS Pages Preface to the 1939 edition . IX Preface to the present edition . xv PART I - CLOUDS CHAPTER I Introduction 1. Definition of a cloud . 3 2. Appearance of clouds . 3 (1) Luminance . 3 (2) Colour .... 4 3. Classification of clouds 5 (1) Genera . 5 (2) Species . 5 (3) Varieties . 5 ( 4) Supplementary features and accessory clouds 6 (5) Mother-clouds . 6 4. Table of classification of clouds . 7 5. Table of abbreviations and symbols of clouds . 8 CHAPTER II Definitions I. Some useful concepts . 9 (1) Height, altitude, vertical extent 9 (2) Etages .... .... 9 2. Observational conditions to which definitions of clouds apply. 10 3. Definitions of clouds 10 (1) Genera . 10 (2) Species . 11 (3) Varieties 14 (4) Supplementary features and accessory clouds 16 CHAPTER III Descriptions of clouds 1. Cirrus . .. 19 2. Cirrocumulus . 21 3. Cirrostratus 23 4. Altocumulus . 25 5. Altostratus . 28 6. Nimbostratus . 30 " IV TABLE OF CONTENTS Pages 7. Stratoculllulus 32 8. Stratus 35 9. Culllulus . 37 10. Culllulonimbus 40 CHAPTER IV Orographic influences 1. Occurrence, structure and shapes of orographic clouds . 43 2. Changes in the shape and structure of clouds due to orographic influences 44 CHAPTER V Clouds as seen from aircraft 1. Special problellls involved . 45 (1) Differences between the observation of clouds frolll aircraft and frolll the earth's surface . 45 (2) Field of vision . 45 (3) Appearance of clouds. 45 (4) Icing . -
Metar Abbreviations Metar/Taf List of Abbreviations and Acronyms
METAR ABBREVIATIONS http://www.alaska.faa.gov/fai/afss/metar%20taf/metcont.htm METAR/TAF LIST OF ABBREVIATIONS AND ACRONYMS $ maintenance check indicator - light intensity indicator that visual range data follows; separator between + heavy intensity / temperature and dew point data. ACFT ACC altocumulus castellanus aircraft mishap MSHP ACSL altocumulus standing lenticular cloud AO1 automated station without precipitation discriminator AO2 automated station with precipitation discriminator ALP airport location point APCH approach APRNT apparent APRX approximately ATCT airport traffic control tower AUTO fully automated report B began BC patches BKN broken BL blowing BR mist C center (with reference to runway designation) CA cloud-air lightning CB cumulonimbus cloud CBMAM cumulonimbus mammatus cloud CC cloud-cloud lightning CCSL cirrocumulus standing lenticular cloud cd candela CG cloud-ground lightning CHI cloud-height indicator CHINO sky condition at secondary location not available CIG ceiling CLR clear CONS continuous COR correction to a previously disseminated observation DOC Department of Commerce DOD Department of Defense DOT Department of Transportation DR low drifting DS duststorm DSIPTG dissipating DSNT distant DU widespread dust DVR dispatch visual range DZ drizzle E east, ended, estimated ceiling (SAO) FAA Federal Aviation Administration FC funnel cloud FEW few clouds FG fog FIBI filed but impracticable to transmit FIRST first observation after a break in coverage at manual station Federal Meteorological Handbook No.1, Surface -
Snow, Weather, and Avalanches
SNOW, WEATHER, AND AVALANCHES: Observation Guidelines for Avalanche Programs in the United States SNOW, WEATHER, AND AVALANCHES: Observation Guidelines for Avalanche Programs in the United States 3rd Edition 3rd Edition Revised by the American Avalanche Association Observation Standards Committee: Ethan Greene, Colorado Avalanche Information Center Karl Birkeland, USDA Forest Service National Avalanche Center Kelly Elder, USDA Forest Service Rocky Mountain Research Station Ian McCammon, Snowpit Technologies Mark Staples, USDA Forest Service Utah Avalanche Center Don Sharaf, Valdez Heli-Ski Guides/American Avalanche Institute Editor — Douglas Krause — Animas Avalanche Consulting Graphic Design — McKenzie Long — Cardinal Innovative © American Avalanche Association, 2016 ISBN-13: 978-0-9760118-1-1 American Avalanche Association P.O. Box 248 Victor, ID. 83455 [email protected] www. americanavalancheassociation.org Citation: American Avalanche Association, 2016. Snow, Weather and Avalanches: Observation Guidelines for Avalanche Programs in the United States (3rd ed). Victor, ID. FRONT COVER PHOTO: courtesy Flathead Avalanche Center BACK COVER PHOTO: Chris Marshall 2 PREFACE It has now been 12 years since the American Avalanche Association, in cooperation with the USDA Forest Service National Ava- lanche Center, published the inaugural edition of Snow, Weather and Avalanches: Observational Guidelines for Avalanche Programs in the United States. As those of us involved in that first edition grow greyer and more wrinkled, a whole new generation of avalanche professionals is growing up not ever realizing that there was a time when no such guidelines existed. Of course, back then the group was smaller and the reference of the day was the 1978 edition of Perla and Martinelli’s Avalanche Handbook. -
PHAK Chapter 12 Weather Theory
Chapter 12 Weather Theory Introduction Weather is an important factor that influences aircraft performance and flying safety. It is the state of the atmosphere at a given time and place with respect to variables, such as temperature (heat or cold), moisture (wetness or dryness), wind velocity (calm or storm), visibility (clearness or cloudiness), and barometric pressure (high or low). The term “weather” can also apply to adverse or destructive atmospheric conditions, such as high winds. This chapter explains basic weather theory and offers pilots background knowledge of weather principles. It is designed to help them gain a good understanding of how weather affects daily flying activities. Understanding the theories behind weather helps a pilot make sound weather decisions based on the reports and forecasts obtained from a Flight Service Station (FSS) weather specialist and other aviation weather services. Be it a local flight or a long cross-country flight, decisions based on weather can dramatically affect the safety of the flight. 12-1 Atmosphere The atmosphere is a blanket of air made up of a mixture of 1% gases that surrounds the Earth and reaches almost 350 miles from the surface of the Earth. This mixture is in constant motion. If the atmosphere were visible, it might look like 2211%% an ocean with swirls and eddies, rising and falling air, and Oxygen waves that travel for great distances. Life on Earth is supported by the atmosphere, solar energy, 77 and the planet’s magnetic fields. The atmosphere absorbs 88%% energy from the sun, recycles water and other chemicals, and Nitrogen works with the electrical and magnetic forces to provide a moderate climate.