Even though predicting weather a mere 24 hours in advance can be very difficult, every month the kind folks at the National Weather Service’s Climate Prediction Center take on the challenge of long term forecasting. While most of us have little practice use for this report, they can be encouraging for those of us still stuck in the dead of winter. I’m definitely getting tired of scraping Wisconsin ice and snow off of my car, so I’m happy to hear that the 3 month outlook forecast calls for warmer temperatures in the western third of country with a pocket of warmer climate that stretches along the northern border states to the Mississippi River Valley. Predictions for the rest of the country are up in the air.
The precipitation forecast calls for below average rainfall in the western and central Gulf Coast Regions along with the Far Southwest. Above average rainfall is predicted for the southern Rocky Mountains and the high plains state. It’s a toss up for the rest of the country.
Can’t forgot about Hawaii – long-term prediction: big surprise….paradise (If you must know, they are predicting average temperature with below average rainfall amounts).
How do they predict the long-term weather?
There are many factors that go into these predictions. An interesting factor is the so-called “memory” effect that ice and snow cover has on climate. For example, if there is a lot of snow on the sun doesn’t heat the ground very well because the energy from the sun is reflected by the snow so the climate “remembers” the recent colder weather. One of the most influential factors is the temperatures of the Atlantic and Pacific Ocean. While El Nino is the most powerful and well-known trend, there are other ocean trends like the Northern Atlantic Oscillation.
Speaking of El Nino, the current El Nino event is winding down and the Pacific Ocean will be ENSO-neutral (El Nino – Southern Oscillation is the full name of the ocean temperature pattern) sometime in the next month or two. In fact, by the summer we may be heading towards La Nina conditions but it’s way too soon to know for sure.
What are El Nino and La Nina?
El Nino and La Nina refers to changes in the average temperatures in the Pacific Ocean that have impacts on weather worldwide. An average increase of 0.5 degrees C in the central topical Pacific is the official definition of El Nino and a decrease of 0.5 degrees C is the definition of La Nina. This doesn’t seem like much, but .5 degrees C of warmer water multiplied by a huge area of ocean is a lot of energy and has a very noticeable effect on global weather.
If you are interested in learning the effects of El Nino on the weather in your location, check out this good website from the National Oceanic and Atomospheric Administartion (NOAA) Here’s a website discussing La Nina effects.
Posted by Tim Roth, author of the political blog Think Anew and Act Anew
1. “Long-Lead Seasonal Outlook – February 15th 2007″, Climate Prediction Center, National Weather Service.
2. “El Nino-Southern Oscillation”, Wikipedia entry