The Pacific Northwest is a veritable playground for outdoor photographers. In any given day I can photograph alpine landscapes, arid desert scablands, lush temperate rainforests and rugged ocean shorelines. One constant in our diverse region is the complex weather. As a native Northwesterner, I have always had a fascination with meteorology and with todays wealth of weather information at our fingertips, its easier than ever to be a weather-savvy outdoor enthusiast.
Get Insider Information Straight From the National Weather Service
Weather forecasts are products, and the producers of those products are meteorologists. TV stations have meteorologists who do a pretty good job of interpreting the weather data sent to them, but if you want to really dig in and get the best information, its best to turn to the National Weather Service (in the United States).
The NWS has offices throughout the country staffed by highly-trained meteorologists who have years of experience in weather forecasting. The NWS meteorologists don’t just look outside and guess at what the weather will be, they use several incredibly complex weather data modeling programs (models), that digest the vast amount of data streaming in from satellites, ground stations, weather balloons, and observers.
This flow of data is so incredibly complex and prolific that it takes super-computer modeling programs to analyze it all. The task of the meteorologists is to scrutinize the projections the computer models spit out. Because each model uses different algorithms to compute their projections, each model will produce a different forecast.
The humans in the mix compare the models and using their experience with the local weather patterns and quirks, they forge a forecast from the projections. Normally, we as weather information consumers don’t get to see behind the curtain as the meteorologists debate the merits of certain models over each other, nor do we get to sit in as they deliberate over their final forecast decisions, but we can sneak a peek into their process and gain valuable insight into the weather headed our way by reading the Forecast Discussion each shift of meteorologists produces at each local office.
Here in Portland, Oregon, the NWS office produces forecasts for all of Northwest Oregon and Southwest Washington State. Their territory includes a large chunk of the Pacific Northwest coast, a long stretch of the Cascade mountain range, and the valleys that connect them all. With the Columbia River cutting right through the heart of the region, the weather dynamics in the Portland NWS territory are very complicated. The temperature and atmospheric pressure differences between the continental air masses east of the Cascades and the maritime environment west of the mountains often create a funnel through the Columbia River Gorge which influences the weather in Portland and throughout much of the area. In short, its a really tough place to predict the weather.
When I am preparing to go out and make photos, I will read the Forecast Discussion (FD) for the NWS office in the area I am going to. Here in Portland, I read the FD every morning. The discussion is the written notes between the shifts of NWS meteorologists who work around the clock to forecast the weather in Portland. The FD is not a forecast product, but instead I think of it as the unfiltered secret forecast for the forecasters. In the FD you will find the reasoning behind the official forecasts along with the dissenting opinions of the meteorologists. This view behind the scenes in the forecast office allows us to see the possible changes in the official forecasts before they happen. It also gives us the opportunity to gauge the confidence of the forecasters, which is surprisingly dynamic.
Think Like a Meteorologist
Pictured above is the main page for the Portland office of the National Weather Service. To find this page for a specific office, visit http://www.weather.gov and type in the name or zip code for the area you are looking for. When the forecast page opens for that area, you will find the link to the forecast office in bold type in the upper left corner of the page. The local office welcome page is packed with links that are organized on the left edge. In the center is a map of the forecast region and any active alerts are color-coded on the map. In this case, the Portland office of the NWS has issued a whole bunch of advisories, watches and warnings for the area. You can spend all day exploring the links on this page, but we are looking at the Forecast Discussion, which is located under the “Forecasts” section of the links on the left side. I have placed a green box around the link.
The Forecast Discussion is published four times each day and follows a pretty informal format. Because this is a discussion between meteorologists and not the plain language product they produce for public consumption, it is laden with jargon and acronyms. It takes a while to learn the language of meteorology, but once you become accustomed to the format of the discussion, it is actually fun to geek out with the scientists as they banter about the weather. To help you dissect the daunting Forecast Discussion, I will tackle one piece by piece. Here is a Forecast Discussion from the Portland office generated on January 19th. Its a rainy day here in Portland, so the discussion is quite interesting:
This title portion has only two things you really need to know: the forecast office making the discussion, and the date and time of the statement. The Synopsis is the Cliff Notes summary of the weather situation at the time of the discussion. If you just read this, you will have a concise idea of whats in store for the day ahead, but not much in the way of meaty information. That comes next.
The Short Term forecast discussion is the most accurate information and the data behind the current forecast. In this section the meteorologist, (in this case, TJ Tolleson), mentions the models making changes to their projections. The NWS runs the models every shift and with new data the models often change their projections. In the discussions the forecasters will often mention which model they are favoring and why, which can be fascinating. Because weather forecasting is not an exact science, yet real-world decisions with large financial costs are made based on the forecasts, the NWS is prone to play it safe with their forecasts and issue advisories and warnings even when they don’t fully believe those weather conditions will materialize. Its nice to have the unfiltered information when making plans. If a word or phrase is printed in blue, you can click on it for a definition.
Reaching into the future more than 48 hours is a challenge for weather forecasters. Long term models fluctuate wildly and in places like the Pacific Northwest two days can bring dramatic changes to the weather. The Long Term discussion portion of the FD is a great place to look when planning a few days out. The meteorologists will discuss the long range models and build a forecast in this section, but they will usually temper it with information about the variables in play that may impact their forecasts.
The National Weather Service plays a crucial role in aviation safety and the aviation portion of the FD is filled with information pertinent to aircraft operators, but for those of us looking for cloud conditions, especially the ceiling (bottom of the clouds) and visibility (clarity of the sky), this section has great information. If you haven’t picked up pilot-speak yet, VFR stands for Visual Flight Rules and means clear skies or patchy clouds that can be flown under or around while IFR means Instrument Flight Rules which are in effect when the clouds are more solid and lower to the ground. For photographers, typically VFR conditions or MVFR (modified VFR) conditions are best for light, but IFR can be great for moody conditions like fog and low, menacing clouds.
In the Northwest our weather typically comes to us directly off the Pacific Ocean, so the Marine portion of the FD is a great place to look for information about what is headed our way. For those of us who spend a lot of time photographing along the coastline, its a vital part of the forecast discussion because it contain the wave and wind information. One thing I like about the marine discussion is the macro view the forecasters often take, explaining the structure of the fronts as they approach the coast. At the end of the discussion, the forecasters will detail the projected wave heights and periods. Along the Oregon and Washington coasts surf higher than 30 happens a few times each winter, and waves in the 10 to 20-foot range is common. The period of the swell is important for photographers as a longer-period swell (more than 10 seconds) will produce more distinct photogenic waves while short-period swell will result in choppy, foamy seas.
At the end of the Forecast Discussion the meteorologists will list any active weather advisories, watches and warnings for the area. As I write this several alerts are running for the area as winds and heavy rain dominate the weather. Any person planning to go outdoors should learn how to interpret and heed any alerts issued by the National Weather Service. Just as the name implies, these special weather statements contain important safety information that can help you plan your time out in the weather.
Weather Knowledge is Weather Wisdom
As you learn to decipher the Forecast Discussion, you will develop your weather wisdom. As someone who spends a lot of time out in the weather, I pride myself on being prepared. By looking to the Forecast Discussion I am one step ahead of those who rely on their iPhone Weather app to tell them whats happening out there. As a landscape and nature photographer, it also pays to know more about how the atmosphere works. By expanding your weather knowledge you will gain insight and appreciation for our dynamic weather and the incredible photos that can result from being in the right place at the right time.