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Seventh Edition, Amendment 18, January 2013 MANOBS Manual of Surface Weather Observations Seventh Edition, Amendment 18 January 2013 MANOBS– Manual of Surface Weather Observations i Seventh Edition, Amendment 18, January 2013 Originating Authority: Weather and Environmental Monitoring Directorate Issued under the authority of the Assistant Deputy Minister, Meteorological Service of Canada ISBN: 978-1-100-20937-1 Cat. No.: En56-238/2-2012E-PDF Information contained in this publication or product may be reproduced, in part or in whole, and by any means, for personal or public non-commercial purposes, without charge or further permission, unless otherwise specified. You are asked to: • exercise due diligence in ensuring the accuracy of the materials reproduced; • indicate both the complete title of the materials reproduced, as well as the author organization; and • indicate that the reproduction is a copy of an official work that is published by the Government of Canada and that the reproduction has not been produced in affiliation with or with the endorsement of the Government of Canada. Commercial reproduction and distribution is prohibited except with written permission from the Government of Canada’s copyright administrator, Public Works and Government Services of Canada (PWGSC). For more information, please contact PWGSC at 613-996- 6886 or at [email protected]. Photographs: © Environment Canada © Her Majesty the Queen in Right of Canada, represented by the Minister of the Environment, 2013. Aussi disponible en français MANOBS– Manual of Surface Weather Observations ii Seventh Edition, Amendment 18, January 2013 Foreword This manual prescribes the standard procedures of the Meteorological Service of Canada for observing, recording and reporting weather conditions. It has been prepared in accordance with internationally recommended procedures as established by the World Meteorological Organization (WMO). Amendments will be issued when warranted. All holders of the manual are responsible for keeping their copies current. When amendments have been entered, this fact should be recorded on the page headed Record of amendments. Inquiries on the content of this manual should be directed to the Meteorological Service of Canada through appropriate channels. This supplement contains the amendments adopted by the MANOBS Working Group. Important note: This amendment will affect the observing standards for SPECI, see 10.3.5.7 and 16.4.4.7. This amendment is to enhance the observing and reporting weather observations practices for Aviation. MANOBS– Manual of Surface Weather Observations iii Seventh Edition, Amendment 18, January 2013 Record of Revisions – MANOBS (Amendment 18) S ection R evision description SPECI criteria SPECI shall be reported for the starting and stopping of freezing Section 10.3.5.3 fog SPECI shall be taken to report the change in intensity from Section 10.3.5.7 moderate to heavy Observer Circulars incorporated in MANOBS Section 3.7.6 OBS 1 – 2001 Weaverboard OBS 1 – 2004 Additional SPECI Observations Criteria at Section 10.3.5.4 Designated Aerodromes (IFR Approach and Alternate Limits) OBS 1 – 2007 List of NC designated sites required to issue Appendix II SPECI for Criteria Temperature Section 12.3.2.1 OBS 1 – 2008 Correction to WMO Code Table 2700 Section 2.15 OBS 2 – 2008 Correction to French MANOBS Section 4.5.2 OBS 4 – 2009 AWOS Pressure Comparison Reading Deletions The content of this chapter has been removed due to the decommissioning of this program. Information about the program Chapter 15, “Pilot-Balloon is still available in the following manuals: Pilot-Balloon Observations” Observations, instrument manual # 60; Pilot-Balloon tables, # 63- 2342; Approximate Altitude of Standard Isobaric Levels for Canadian Pibal Stations, SPC. The content of this chapter has been removed. All information Chapter 16, “Decoding about decoding Autostation reports is available in the following autostation reports” manual: Reference Guide to the Automated Weather Observation System. MANOBS– Manual of Surface Weather Observations iv Seventh Edition, Amendment 18, January 2013 S ection R evision description Chapter 17, “Abstracting The content of this chapter has been removed since this chapter and recording references old practices which are no longer used. Refer to supplementary data, MANOBS Amendment 17 to view this chapter. monthly climatological summary – Form 63- 2320” The content of this chapter has been removed since this chapter Chapter 18, “Abstract of references old practices which are no longer used. Refer to wind” MANOBS Amendment 17 to view this chapter. MANOBS– Manual of Surface Weather Observations v Seventh Edition, Amendment 18, January 2013 Record of Amendments AMD No. E ffective date Entered by Date of entry MANOBS– Manual of Surface Weather Observations vii Seventh Edition, Amendment 18, January 2013 Table of Contents Page Foreword .............................................................................................................................. iii Record of Revisions – MANOBS (Amendment 18) ........................................................... iv Record of Amendments ..................................................................................................... vii Table of Contents ................................................................................................................ ix Introduction ........................................................................................................................... 1 Part A Observing Procedures – General ..................................................... 13 Chapter 1 Sky .............................................................................................................. 1–15 1.1 Celestial dome .................................................................................................... 1–15 1.2 Layer determination ............................................................................................ 1–15 1.3 Layer identification ............................................................................................. 1–16 1.4 Layer amount and opacity .................................................................................. 1–17 1.5 Direction of motion of layers ............................................................................... 1–19 1.6 Height ................................................................................................................. 1–20 1.7 Ceiling ................................................................................................................ 1–22 1.8 Method of determining heights of layers ............................................................. 1–22 Chapter 2 Visibility ..................................................................................................... 2–33 2.1 General ............................................................................................................... 2–33 2.2 Prevailing visibility .............................................................................................. 2–33 2.3 Determination of prevailing visibility ................................................................... 2–33 2.4 Units of measure ................................................................................................ 2–36 2.5 Variable visibility ................................................................................................. 2–36 2.6 Guides in determining visibility ........................................................................... 2–36 Chapter 3 Atmospheric phenomena ......................................................................... 3–41 3.1 General ............................................................................................................... 3–41 3.2 Tornadoes and Waterspouts (+FC) .................................................................... 3–41 3.3 Thunderstorm (TS) definition .............................................................................. 3–43 3.4 Precipitation ........................................................................................................ 3–43 3.5 Obstructions to vision ......................................................................................... 3–48 3.6 Visibility reduced below eye level ....................................................................... 3–53 3.7 Measurement of precipitation amounts............................................................... 3–53 3.8 Depth of snow on the ground ............................................................................. 3–58 3.9 Intensity of precipitation ...................................................................................... 3–58 3.10 Intensity of precipitation with an obstruction to vision ......................................... 3–62 3.11 Character of precipitation ................................................................................... 3–62 3.12 Notes on unusual weather .................................................................................. 3–63 MANOBS– Manual of Surface Weather Observations ix Seventh Edition, Amendment 18, January 2013 Chapter 4 Atmospheric pressure .............................................................................. 4–65 4.1 General ............................................................................................................... 4–65 4.2 Barometric pressure computations ....................................................................
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