PAOC Spotlights

Got Weather?

Tue January 4th, 2011
Allison Wing

The Tech

One way in which PAOC students share their meteorological expertise with the community is by serving as staff meteorologists for The Tech, MIT's 130 year old student newspaper. This year's staff meteorologists for The Tech are undergraduates Roman Kowch '12 and Vince Agard '11 and PAOC graduate student Allison Wing.They are charged with the task of writing a full forecast and weather discussion for each issue of the The Tech, which is published twice a week during the academic year, once a week during IAP, and once a month during the summer. There are three parts to each forecast. First, the meteorologist creates a 4-5 day forecast for Cambridge, MA, including predictions of the high and low temperatures, wind speed and direction, and type of weather (clouds, precipitation, etc...). Second, the meteorologist prepares a weather map showing the position of high and low pressure systems, fronts, and precipitation over the continental U.S. for the date that particular issue is published. Finally, the meteorologist writes a short paragraph describing some aspect of the weather. Often this means discussing the synoptic weather conditions over the next few days, and how this leads to the particular weather forecast. Sometimes other topics of interest are discussed, such as any current hurricane activity, climate predictions, weather records. The forecasts are published in the print edition of the The Tech, and also appears on their website.

How does one go about making a weather forecast? The first step is to examine the current weather conditions, by looking at satellite and radar images, as well as ground-based station observations. Satellite images of clouds and water vapor are important for understanding the large scale picture of what is happening currently. In addition to examining data from the ASOS stations across the country (in which ASOS is the United States' primary automated surface weather observing network), we are lucky to have our own weather station here at MIT. On the roof of the Green Building is a fully equipped, fully functioning, state of the art weather station from which real-time weather information is streamed as KMACAMBR9 aka MIT (Green Bld Roof), Cambridge, MA, to the Weather Underground website. Used in conjunction with other real-time meteorological data, such a local source of current weather is an invaluable tool for understanding the current meteorological conditions.

After examining the current observations, the next step is generally to look at the output from global and regional forecast models, run by the National Centers of Environmental Prediction (NCEP). These highly complex numerical models solve the physical equations that describe how weather evolves (equations for wind, pressure, temperature, etc...) by iterating them forward in time from a set of initial conditions (the current observations). Various parameterizations help the model forecast things which it cannot resolve (such as convection). Looking at maps of sea level pressure, surface and upper air temperature, precipitation, as well as other variables, allows the forecaster to determine the large-scale weather pattern expected over the next several days. Then, to determine a precise number, for maximum and minimum temperatures for example, the forecaster looks at the model output interpolated to the location of interest. Model output statistics (MOS) are also run on the model output, which generally improve the prediction; this data is also available to use. This is usually a decent "first guess" for what the forecaster thinks the weather will be, but they come to the final forecast by comparing different models, taking into account known local biases, while keeping in mind what is happening in the large-scale weather pattern and how it all fits together. Given the chaotic nature of the climate system, making a perfect forecast is nearly impossible, but the meteorologists who forecast for The Tech are able to give readers a good idea of what the weather will be like the next few days. In addition to providing this service for the community, forecasting for The Tech is a good application of the theory learned in classes and is real-world forecast experience that helps further the forecasters knowledge of how the weather works.

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