Blogs

Here we are—in March 2015—and we’ve got... above-average temperatures in the subsurface equatorial Pacific. westerly wind anomalies near the surface across the western tropical Pacific Ocean.  El Niño favored through the Northern Hemisphere Summer with a 50-60% chance (see March 5th ENSO update and blog post). Unbelievably, it was exactly last year at this time (March 2014) when we were watching the progress of a strong downwelling Kelvin wave crossing the equatorial Pacific (#1), in part driven by westerly wind anomalies (#2), and some folks were getting excited about a potentially strong El Niño by the end of 2014 (#3).  It’s similar enough to have us rubbi…   Read article

Last November, I wrote a post discussing the Climate Prediction Center’s (CPC) temperature and precipitation outlooks for winter (December 2014 – February 2015).  Since we’re now into March, it seems appropriate for me to look back and see how they did.  In that post, I discussed the probabilistic nature of the outlook, and what the favored categories (above-, near-, and below-average) for winter temperature and precipitation were judged to be. As a reminder, and if you haven’t memorized that post, the outlooks favored above-average temperatures in Alaska, much of the West, and also in northern New England, and below-average temperatures in the south-central and southeastern par…   Read article

This is a guest post by Dennis L. Hartmann, who is a professor in the Department of Atmospheric Sciences at the University of Washington in Seattle.  He literally wrote a textbook that was the foundation for our climate training (webpage and CV), so we’re pretty enthused he’s guest blogging with us—to put it mildly. Still, the Climate.gov managing editor asks us to remind our readers that all blog posts convey the opinions and ideas of individual bloggers, not NOAA.This post offers one expert’s view on a question that many scientists are exploring and debating. So far this winter it has been warm and dry in the West and cold and snowy in the East.  As I write from Seattle, it is…   Read article

Over the last several months, we’ve seen warmer-than-average sea surface temperatures (SSTs) in the tropical Pacific, including the Niño3.4 region, which we track as one indicator of El Niño. The seasonal Niño3.4 Index has been at or above 0.5°C since September, and the most recent weekly Niño3.4 index was +0.6°C. The El Niño/Southern Oscillation (ENSO) is a coupled phenomenon, though, so we also monitor the atmosphere for signs that it is responding to those positive SST anomalies. For the last few months, we’ve been seeing some suggestions of borderline atmospheric El Niño conditions, but until this month we were below that borderline. This month, we’ve finally crept above it, and thus …   Read article

In my first installment about seasonal verification, I showed how using our eyes to verify seasonal forecasts is easy, but can be misleading—so it is often better to use “metrics” to grade our forecasts and see how well they did.  Part 2 looked more closely at one such way to grade our forecasts, called the Heidke Skill Score (HSS). The HSS breaks down the forecast into grid boxes spanning the United States, and then for each grid box showing the forecasted category (above-normal, near-normal, below-normal) with the highest probability, we check how often the forecast was the same as reality.   As a refresher, please check out the first figure in my last post. If movie trilogies…   Read article