Sunday, March 4, 2012

Severe Weather Possible in the Long Range

Yesterday, I mentioned how the ridge currently in the Gulf of Alaska will be shifted south and a new low pressure system regime will take over.

Now, looking at the individual 12z GFS Ensembles, it looks like a good portion of the East US may be under the gun at some point in the next few weeks.

Here's one of the GFS Ensembles' 6-10 day 500mb height anomalies forecast. The ensemble member shows the Gulf of Alaska covered by a deep low pressure system. Also, there is a large ridge in the North US and a low pressure system in the south central US. I worry that the warm Gulf air moved both by the strong ridge will quickly interact with any low pressure system that may be present along the area delineated for a low pressure in the area.

The deep low in the Gulf of Alaska (GOA) will persistently spit out low pressure disturbances that will hit the US and come onshore to produce precipitation. As long as this vortex of low pressure is in the GOA, there will be a somewhat continuous threat of precipitation- from snow to severe weather.

Here I have delineated the area I think may be at risk with the low pressure systems that formulate in the Southern Plains. If they ride along the outskirts of the ridge, the Midwest may very well get in on the action. It comes down to this- as long as the Gulf of Mexico (GOM) is 'open for business' with warm, moist air flowing on land, severe weather is possible.

Now, the tornado threat will depend on how strong a system is and the proximity to the jet stream that will be displaced north. The vortex in the GOA makes for a cause-effect relationship that produces a ridge of high pressure in much of the east half of the US. That ridge then pushes the jet stream north, possibly as far north as the Canada/US border. If the storm system is weak and far south, the jet stream may not latch onto it and lessen the tornado threat. If the storm system is stronger, the jet stream may catch it and increase wind speed and the tornado threat.


Long Range Severe Weather Prediction Coming Out at 3:00 PM CST Today

Using new indices I have gathered, I will be publishing a long range prediction on possible severe weather over a portion of the country in the next few weeks.

It will be published at 3:00 PM CST today.