A Beginner's Guide to Weather Forecasting by Aldrin Gabuya


Weatherman doing an on-screen weather forecast [Photo credit: eonline.com]

     Weather has been a big part of our lives, rain or shine. Every day, whenever we tune in to the news on TV, radio, or the Internet, we witness weathermen/women delivering weather information to the public as they point to different areas of the background projecting satellite imagery and other graphics. People want to know the weather conditions for tomorrow or a few days later so they can plan for special occasions such as a flight or boat ride, or for farmers, when to plant or harvest, or even just for their daily routines. 

PAGASA weather forecaster pointing to Typhoon Basyang satellite
imagery. [Photo credit: guiengarmafiles.wordpress.com]

     The practice of predicting the atmospheric and weather conditions to be experienced for a given time at a given location is called weather forecasting. This is the most practical application of meteorology, the scientific study of the atmosphere. It involves the use of observation, knowledge of weather trends and patterns, and computer models by meteorologists, scientists who specialize in the field.

     Every country has its respective weather agency, mostly handled by its government, to perform these activities. The official weather agency of the Philippines is the Department of Science and Technology - Philippine Atmospheric Geophysical and Astronomical Services Administration (DOST-PAGASA).

      But how is weather forecasting done? As in science, everything undergoes a step-by-step process. Meteorologists conduct the scientific method every day, or even every hour to determine the future weather conditions. Together with their human senses, they use several weather instruments.

     First, as several historical thinkers like Confucius and Carl Sagan have stated, in order for us to understand the present and future, we must know the past. Scientists have to recall and examine what happened to the weather and the reasons for it in a certain area in the past. They analyze previous observations and measurements of weather parameters such as temperature, humidity, air pressure, and rainfall from archived data. 

    They also take into consideration the current weather conditions in their respective area by gathering data at time intervals such as every hour, every 3 hours, and so on. They gather this data from instruments such as satellites, radar, automatic weather stations (AWS), weather balloons, weather maps, and their own data tabulations.

Weather instrumentation. [Photo credit: Veronica de la Vega]

PAGASA's mobile Doppler radar. [Photo credit: media.philstar.com]

     A central weather agency receives hundreds, to thousands, and even millions (on a global scale) of data every day. But sometimes, the agency can receive incomplete data - for instance, some weather stations may be remote or be experiencing technical difficulties, affecting the precision of the forecast. Upon "filling in the holes", meteorologists conduct data assimilation, where they make estimated projections by combining available observations and the forecasts based from it.

    This data is then managed upon making a numerical weather prediction (NWP) model. Also known as a forecast model, it is a computer-generated atmospheric model depicting simulations of possible future weather conditions, based on calculations for a specified time frame. Meteorologists use supercomputers for the activity to conduct the complex computations and illustrations. 

     Examples of NWP models are the Global Forecasting System (GFS) model, and the European Centre for Medium-Range Weather Forecasts (ECMWF) model, which both cover the global atmosphere. Their raw models are processed distinctly for local forecasts by a region's respective weather agency (e.g. North American Mesoscale (NAM) Forecast System). 

Animated simulation of NAM forecast radar reflectivity, from 0000 UTC on 
July 10, 2012 to July 13, 2012, at 1200 UTC. [Photo credit: www.ncdc.noaa.gov]

     Since the basis for the NWP model is the current weather conditions, it is only an extrapolation, also subject to error or uncertainty, especially for longer forthcoming periods. Understanding these weather patterns is a must for a weather forecaster. More experienced forecasters throughout their career encounter cyclic weather patterns (e.g. monsoons) which they use as a guide for their predictions. 

     Of course, different meteorologists may have differing analyses and interpretations of some aspects of a data. Hence, it is very important for an agency to collaborate and discuss among themselves the findings and agree upon a conclusion before making the forecast for a certain date, to be shown to the entire covered region via TV, radio, newspaper, or the Internet. This is probably the most critical part of the said endeavour.

Collaboration among PAGASA meteorologists. [Image credit: politics.com.ph]

       Due to the complexity of atmospheric dynamics and how it keeps changing over time, ensuring an accurate forecast can be very challenging, particularly for longer periods. This phenomenon may be due to the Butterfly Effect. With its origins in chaos theory, the butterfly effect describes how in a complex nonlinear system such as the weather, even small changes in its initial state can result in a significantly different result - hence, these uncertainties limit the accuracy of weather models to a few days in the future. Because of this, techniques like ensemble prediction systems evolved to counter this uncertainty by trying to obtain a range of possible future states. 

     Though I am pursuing an astronomy course, I am aspiring to be a meteorologist, providing weather information to the public and helping them in that way. I also want to inspire my fellow youth to pursue a career in science, technology, engineering, and mathematics (STEM). As DOST-PAGASA's slogan states, "Tracking the sky, helping our country."

Weather forecast process. [Photo credit: bbc.co.uk]

      For the latest weather information in the Philippines, please visit the official website of DOST-PAGASA and meteorological agencies worldwide. Stay safe, and be a weather-wiser Filipino.


REFERENCES: 

1. First steps. (2015, October 19). Retrieved from MetOffice: http://www.metoffice.gov.uk/learning/science/first-steps

2. Muller, G. (2013, January 24). How do meteorologists at AccuWeather make your forecast? Retrieved from Accuweather.com: http://www.accuweather.com/en/weather-news/how-do-meteorologists-make-forecast/4716627

3. Numerical Weather Prediction. (n.d.). Retrieved from NOAA - National Centers for Environmental Information (NCEI): http://www.ncdc.noaa.gov/data-access/model-data/model-datasets/numerical-weather-prediction

4. Warrilow, C. (2012, February 12). Students ask: How do meteorologists predict the weather? Retrieved from GPB Blogs: http://www.gpb.org/blogs/talking-up-a-storm/2012/02/15/students-ask-how-do-meteorologists-predict-the-weather

5. "Weather Forecasting". World of Earth Science. (2003). Retrieved from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3437800646.html

1 comment:

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