Synoptic Analysis and Forecasting

An Introductory Toolkit

Shawn Milrad

• Publisher: Elsevier
• Year: 2017
• ISBN:
  9780128092569
• Topic: Ciencias biológicas
• Subtopic: Ciencia medioambiental

Synoptic Analysis and Forecasting: An Introductory Toolkit provides the bridge between the introductory fundamentals of a meteorology course and advanced synoptic-dynamic analysis for undergraduate students. It helps students to understand the principles of weather analysis, which will complement computer forecast models. This valuable reference also imparts qualitative weather analysis and forecasting tools and techniques to non-meteorologist end users, such as emergency/disaster managers, aviation experts, and environmental health and safety experts who need to have a foundational knowledge of weather forecasting.

• Presents the fundamentals of weather analysis and forecasting
• Offers clear accessible writing aimed at students from a variety of mathematical backgrounds
• Discusses the reading and interpretation of surface observations and METAR code, processes associated with the motion and intensity of cyclones and anticyclones, and quantitative and/or qualitative diagnosis of processes associated with ascent and descent

1

Meteorological Conventions

Abstract

Meteorological observations and forecasts use a universal time system known as Universal Coordinated Time (UTC) or Zulu (Z). It is vital to be able to convert time in Z to whichever local time zone the observer or forecaster is working in. While most meteorological variables use the MKS unit system, there are some exceptions such as temperature, wind speed, and pressure. Temperatures are generally reported in degrees Celsius, with one major exception: surface temperatures in the United States, which use degrees Fahrenheit. Wind speeds are generally reported in knots, while atmospheric pressure most commonly is given in millibars, equivalent to the hectopascal. Finally, wind directions are reported in degrees as where the wind is coming from, using a coordinate system unique to meteorology.

Keywords

Meteorological conventions; Units of measure; Time zones; Zulu time; Temperature; Wind speed and direction; Atmospheric pressure

1.1 Time Zones and Zulu (Z) Time

Weather analysis and forecasting are global pursuits. The forecaster should not limit him or herself to learning only about their city, region, country, or continent. Because numerical weather prediction models and forecasts are produced across the globe, it is crucial that the meteorological enterprise operates largely independent of time zones. In fact, the word synoptic is derived from Greek, meaning “at the same time.”

Meteorological observations and forecasts use Universal Coordinated Time (UTC), otherwise known as Zulu (Z)¹ or Greenwich Mean Time (GMT), which operates on a 24-h clock. This system was first devised in the United Kingdom and is based on the time at Greenwich, England, which is located on the Prime Meridian (0° longitude). In order to become familiar with typical meteorological analysis and forecast times, it is crucial to know how to convert from Z to your local time zone and vice versa.

The conversion from Z to your local time requires knowledge of how many time zones you are away from Greenwich, England, and what time of year it is (i.e., whether it is Daylight Saving Time). For example, 12Z is noon in Zulu time; at the same time, the US east coast is 7 a.m. local time in the winter (Eastern Standard Time) and 8 a.m. local time in the summer (Eastern Daylight Time). In California and British Columbia, 12Z is 4 a.m. Pacific Standard Time and 5 a.m. Pacific Daylight Time, respectively. Table 1.1 details the time conversion and local times for various locations across North America at key meteorological observation times.

Table 1.1

Examples of Time Conversions From Zulu (Z) Time for Specific Locations Across North America

Time Zone	Cities Included	Hours Behind Z	00Z	12Z
Atlantic Standard Time (AST)	Halifax, Hamilton (Bermuda), San Juan (Puerto Rico)	4	8 p.m. AST	8 a.m. AST
Eastern Standard Time (EST)	New York City, Miami, Toronto	5	7 p.m. EST	7 a.m. EST
Central Standard Time (CST)	Chicago, Houston, Winnipeg	6	6 p.m. CST	6 a.m. CST
Mountain Standard Time (MST)	Denver, Albuquerque, Calgary	7	5 p.m. MST	5 a.m. MST
Pacific Standard Time (PST)	Los Angeles, Seattle, Vancouver	8	4 p.m. PST	4 a.m. PST
Alaska Standard Time (AKST)	Juneau, Anchorage, Nome	9	3 p.m. AKST	3 a.m. AKST
Hawaii Standard Time (HST)	Honolulu, Hilo, Pearl City	10	2 p.m. HST	2 a.m. HST

For Daylight Saving Time, one fewer hour should be subtracted from Z.

1.2 Common Units of Measurement

Most meteorological variables and calculations are handled using standard metric (SI) meters-kilograms-seconds (MKS) un...