Saturday, 4 May 2013
It’s hard to believe we are already halfway through the first week of May! You wouldn’t know if you are looking at forecasts from the Storm Prediction Center showing a lot of “See Text” areas or looking at the way the weather has been the last several days. With historical snowfall and record low temperatures occurring from Colorado to Kansas and other areas of the Great Plains, it just hasn’t felt like spring. Not at all. In fact winter hasn’t given up. But I’m finally seeing the beginning stages of spring and yes, the storm chasing season, coming back to life!
Right now as I type, a large area of thunderstorms (convection) continues to grow over the Indian Ocean from just east of Africa to just west of Indonesia (seem image below). This is the birth of a new MJO (Madden Julian Oscillation) wave. And the future strength and especially movement of this MJO could have a significant impact on the storm chasing season in late May or early June. So it has this storm chaser’s full attention.
Satellite image on May 4, 2013 over the tropics from eastern Africa to the Indian Ocean and Indonesia area. The MJO convection is circled.
Ok, please brace yourself for three paragraphs of a bit of meteorology (weather nerd) talk. It’s necessary to explain how all this stuff can result in large tornadoes! Below is the MJO forecast for the next 15 days from the European Ensemble. Notice how most members bring the MJO to phase 4 in about two weeks while a few bring it all the way to phase 5. Phase 4 would certainly bring more troughs to the west coast of the U.S., but it would be a split flow type pattern with a continued ridge over western Canada to Alaska (not shown). This would probably bring severe weather setups to the southern plains (TX/Oklahoma) from the subtropical jet, with some limitations given that the main jet energy source would be blocked.
MJO forecast for the next 15 days from the European Ensemble valid May 4, 2013.
However, the greater pattern impacts which would bring the potential for a lot more significant storm chasing setups to the Great Plains, would occur if the MJO makes it out to phase 5 (see image below). Phase 5 would bring a full jet stream extension across the northeast Pacific (ridge just south of Alaska) and a corresponding trough to the western U.S. and western Canada with a ridge over the southern U.S. Basically, it would bring a great synoptic scale weather pattern for severe weather and potentially tornadoes to the central parts of the U.S. including the Great Plains. Just how long this good chase pattern lasts would largely be dictated by just how long the convective feedback remains in phase 5.
500mb height anomalies for MJO phase 5 during the month of May. Should this occur in late May it suggests a favorable storm chasing pattern.
Ok, now that I’ve talked about how great it would be for storm chasers if the MJO makes it all the way to phase 5 and those convective feedbacks remain in place, we can talk in a bit more realistic sense. It’s a bit unclear just exactly how quickly and how far east the MJO will move over the next 15 days. I’m not seeing a lot to suggest significant eastward progression right now, based on current data across Asia and the Indo-Pacific region. Though some data strongly suggests quick eastward movement over the next week, or at the very least continued strength of the MJO wave. Beyond that again it’s unclear how far east this MJO will go at this time. But the one thing that convection has going for it is warm sea surface temperatures from the Indian Ocean all the way to the western Pacific. So again, it could be just a matter of time.
It’s definitely interesting to note the latest European Weekly model brings a pattern change during the last 7-10 days of May, bringing a trough to the western U.S. and a ridge to the eastern and southeastern U.S. This would loosely fit the approximate MJO phase 5 timing if it indeed takes perhaps 15 or 20 days to make it that far east.
In a nutshell I think it’s safe to say it’s just a matter of time before the chase season comes back to life! And this shouldn’t really be a surprise. I mean, mother nature cannot just keep the pattern perpetually crappy for the remainder of the season. Something’s gotta give. And that ‘give’ is showing up right now in the form of growing convection over the Indian Ocean. By sometime in late May that convection could cause latent heat feedbacks over the Pacific jet stream that will in turn force a series of strong troughs across the western U.S. and a ridge over the southern and eastern U.S. Finally, this will all combine with deep moisture from the Gulf of Mexico to bring supercells and tornadoes to the Great Plains.
Right…if only it were THAT simple! But the pieces of the puzzle are starting to come together. It’s more than just hope. The data says keep your eyes open and be patient.
It’s just a matter of time….
Jim
