There was little change in the thermal anomalies for La Nina this week. The surface remained nearly the same while the Subsurface continued to steadily moderate. The support for cold anomalies for La Nina is steadily fading away, which would support what the model guidance has been suggesting the past few weeks.
The atmospheric influence of La Nina is starting to show slow signs of weakening over the past week. However, I don’t see any evidence of a rapid collapse of La Nina’s influence on the atmosphere, at least in the short and medium terms. Given the observational data, La Nina is likely to remain an influence on the weather pattern into early Spring. As a result, we should continue to expect the Subtropical jet stream to continue to feature the same atmospheric characteristics we have seen thus far into March with an occasional ridge developing between the Gulf Coast and the Bahamas from time to time.
The latest model guidance continues to suggest a weakening La Nina through the Spring followed by a cold neutral environment through the Summer. I should note we do have one model solution that brings a weak El Nino into the fold, but that is an outlier. This data would suggest that the Subtropical jet stream will remain weaker than normal through the Spring and into the Summer. As a result, the Polar jet stream will be the dominant jet stream and may support robust shortwaves and cold air displacement that could continue to support high latitude blocking and also an increased potential for severe thunderstorm outbreaks from the central Plains to New England for the Spring and Summer months.