Long Range: How and why this weeks ridge positioning is critical

You may have heard over the past few days (or weeks) that a large ridge is developing throughout the Central portions of the United States. You definitely have heard about this ridge if you have agriculture interests — which is who we’re really speaking to in this afternoon’s Long Range Update. The development and positioning of this ridge has been a hot topic for a while now, and after some forecast models suggested the ridge would encompass much of the Eastern US, it has developed well west of those regions.

But, truth be told, there is a  lot more to the forecast than “the ridge is here” or “the models were wrong”. Many professionals, no matter what sector they focus on, will tell you the same thing: Understanding the process of how things occur is more critical than almost everything else. So while we provide the forecasts each day, we like to take the time to explain why things are happening, how they happen, and how we believe they will unfold down the road.

Why is the ridge developing, and why has it formed where it has?

Over the past several days, a large ridge in the atmosphere’s mid and upper levels developed over the Western and Central United States. Ridges of high pressure that form with such vigor and breadth, more often that not, aid in the development of above normal temperatures and dry conditions underneath their coverage area. The circulations around higher pressures in the low levels, and circulations around the ridge in the mid and upper levels, support warmer south/southwest wind directions.

A closed low developing in the Gulf of Alaska has enhanced ridging in the West/Central USA.

A closed low developing in the Gulf of Alaska has enhanced ridging in the West/Central USA.

The roots of this ridge can be traced back to the Northern Pacific Ocean, and these roots will become critical as we try to pin down where the ridge will end up in the next few weeks. In response to tropical forcing and adjustments in angular momentum (we’ll leave those for tomorrow’s technical discussion) the Pacific Ocean saw a reshuffling of heights a few weeks ago. This eventually lead to the development of a large closed low in the Gulf of Alaska (we highlighted it in blue).

In response to this large, closed low, heights rose ahead of it — into the Western United States. This allowed a large ridge to form and bring warmer air via south/southwesterly winds from the Southwest United States. It is important to note that the closed low in the Gulf of Alaska can modulate the ridge’s strength and location! This is a critical point in the forecast over the next few weeks.

What impacts will this ridge have over the next several days? 

Large mid and upper level ridges are important for a few reasons; none more significant than the fact that they can dominate the weather pattern over a large spatial coverage area. We discussed how it can quickly become warmer than average and dry underneath them, but what about their surroundings? The truth is that these ridges can often serve as highways for disturbances along their periphery.

The track of disturbances can be visualized along a height gradient in the atmosphere.

The track of disturbances can be visualized along a height gradient in the atmosphere.

Think of it this way: As the circulation of the ridge itself becomes dominant, disturbances that track towards it will be forced up and along its periphery. SO disturbances approaching from the Pacific Ocean will track along the edge of the ridge, over its top (like a roller coaster) and then fall southeastwards on the ridges eastern edge. This is known affectionately as a “ring of fire” pattern, because of the ridge’s warm impacts and the disturbances which track around it. You can visualize this with our 7 Day Temperature Anomaly Forecast below (updated multiple times per week for clients).

The unfortunate truth is that the ridge is currently placed in a poor position for agriculture interests. Underneath the ridges control are areas that remain dry and warm (the Western AG regions) and along the ridges periphery are regions that have been active and wet (Central and Eastern AG regions). The ridge’s position and dominance will only reinforce this.

When analyzing the mid level height pattern on most forecast model guidance over the next few days, it is easy to visualize the track and location of disturbances which will move atop the ridge and then into the Central and Eastern AG Belt. Opportunities will exist for showers and thunderstorms in those regions, and possibly severe weather as well.

Temperature anomaly forecast through the next 7 days.

Temperature anomaly forecast through the next 7 days.

Where will this thing move in the next few weeks?

This is, as always, the trickiest part of the forecast. Most global model and ensemble suites suggest a very interesting pattern evolution over the next 2 weeks or so, which features a very brief reshuffling pattern in the Pacific Ocean, and will offer some opportunity for a brief shakeup. This will, however, be short lived. Let’s dive in to exactly how and why this is occurring.

Notice how the GFS and ECMWF Ensembles both show the large closed upper level low we mentioned earlier in the Gulf of Alaska dissipating and shifting northeastward. This is critical — it allows the mid level flow in the atmosphere to attain some progressiveness to it. As a result, the ridge may collapse slightly eastward and adjust itself over the Central and Eastern AG regions — briefly. 

Very quickly, however, all medium range model guidance agrees that tropical forcing and the hemispheric pattern will snap back into place, with another closed mid level trough developing in the Gulf of Alaska. This suggests that even after a brief departure from the pattern we are locked into currently, the ridge will likely redevelop back to the West around the 15th of July.

After a brief relaxation and possibly eastward movement, a large ridge will become re-established in the West/Central US by 7/15.

After a brief relaxation and possibly eastward movement, a large ridge will become re-established in the West/Central US by 7/15.

Overall Impacts and Thoughts…

As we move towards the end of the week, it is important to note that many of the Western AG Belt regions are experiencing drought (The Dakotas to name one area) and warm temperatures. This does not look likely to let up over the next 7 to 14 days — in fact, it may be reinforced by the presence of the ridging mentioned above.

Meanwhile, much of the Central and Eastern AG Belt has experienced active conditions — and this also looks likely to continue through the middle of the month. Persistence of this pattern looks possible through at least 7/20, when there are some initial signals that the Pacific may reshuffle once again.

Stay tuned and make sure to check back for further updates tomorrow. If you are interested in signing up to receive briefings, videos, consultation, and discussions like this one every day — just give us a shout. You can also read more about our products right here. We work with each of our clients individually and take pride in developing a program tailored to them, so we don’t offer any cookie-cutter products. When you contact us we will try to set something up that works best for you.

Otherwise, have a wonderful Thursday afternoon and evening!

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