MJO Forecast and Stratospheric Warming: Impact of Extremes

Summary: Historical analogs point to the likely impacts of a weak stratospheric polar vortex and an amplified MJO forecast In a dramatic break with the pattern of recent years, this winter has seen strong and persistent high-latitude blocking that has produced unusual cold across most of Russia and East Asia. The Arctic Oscillation has been[…]

What Is Forecast Reliability?

Introduction to Forecast Reliability In talking about the quality of weather forecasts, it is common to hear the words “reliable” or “unreliable” used in common parlance as well as in specialized and technical settings. It’s therefore worth considering what the notion of “reliability” means to different people, and how we use this notion in connection[…]

Statistical Forecasts in Action

Introduction Last year at about this time, the World Climate Service highlighted a new effort to develop a statistical forecast capability for the subseasonal time frame (weeks in advance), and last summer a new World Climate Service product was released. Since then, the statistical forecast scheme, known as Sub-R, has been delivering week 3-6 temperature[…]

Making Sense of Long Range Forecasts

In an October 31 blog post, distinguished meteorologist Cliff Mass of the University of Washington commented on the degree of usefulness of long range forecasts, with the title, “Extended Forecasts Are Not Reliable“. Dr. Mass highlights the lack of deterministic skill of temperature and precipitation forecasts in the dynamical forecast models beyond two weeks and[…]

Example Model Consistency Display

Ensemble Dynamical Forecast Model Calibration for Seasonal Climate Prediction

The World Climate Service uses a special technique called “calibration” to ensure the forecasts of probabilities of weather events are properly estimated. It’s a fairly complex technique that requires processing a significant amount of retrospective data from dynamical models such as the CFSv2 and the ECMWF. The subseasonal and seasonal dynamical model calibration methodology used[…]

Week 3 temperature probability forecast

Seasonal Forecasts – Who To Believe?

A recent article in the Wall Street Journal, quoting World Climate Service scientist Paul Knight, commented on the contradictory winter forecasts issued by two competing versions of the U.S. “Farmer’s Almanac”: https://www.wsj.com/articles/will-winter-be-nasty-or-nice-depends-which-farmers-almanac-you-read-11545929300 While the discussion is lighthearted, and some might say the forecasts themselves are not to be taken seriously, the article illustrates the popular[…]