Since I want to start these mid- to long-term forecasts, I always want to start with the “baseline” and what exactly might affect the pattern across the northern hemisphere. This said background starts with the state of the tropics and how and where the MJO (if there are coherent waves) can propagate. In this current case, we have a fairly coherent wave of MJOs emerging from the Western Pacific and propagating eastwards across the Pacific Ocean, circling the Western Hemisphere over the next 1-2 weeks. We see this on hovmoller, where again blue/green indicates a higher level divergence and that is where our convection is.
Once again coming out of the foundational metaphor, we have composites collected over time to try to best match the generalized superior model like when the MJO is in a certain location across tropical region. We see phase 7 through 8 verbatim, which is what we’ll see happen in relation to the MJO phases through mid-April. Below, a few features stand out such as -NAO (positive elevation across Greenland to southern Canada) and positive elevation across Alaska. Across CONUS, below-average elevations exist throughout the Northeast along with trenches off the West Coast. Now compare this to what pods are showing at 500mb.
No wonder we see our -NAO growing with altitude receding into Greenland and Hudson Bay with elevation actively growing throughout Alaska. Across the US, we see a trench forming across the Great Lakes, the Ohio Valley and the Northeast with a ridge forming across the central US, with below-average elevations off the West Coast. Pretty similar, don’t you think?
On the surface, this gives us the risk of below-average temperatures across the Northern Plains, the Great Lakes and into the Northeast. Moderate to above average across the Plains and Midwest, with temperatures continuing to be below average across the West. It’s the end of April now, so below average here is quite an approximation, but the point is that as stated before, the general pattern going forward is not “hit and hold”; instead, it’s fleeting with a few interesting shots but without the noticeable heat we’ve seen all week! So, if you may be wondering about places with record high temperatures and whether this is a future trend, let’s answer that question briefly: no. It looks like by early May we’ll see more of a banding and more widespread above average temperature, but we’ll hit that point when we get there!
About the author
Hello! My name is Armando Salvadore and I am a Mississippi State graduate with a Bachelor of Professional Meteorology and an Activity Meteorologist working in the Private Sector. Stay tuned if you like technical, exotic, and general weather tweets! Also big on long-range forecasting as well! Twitter: @KaptMands