Wednesday, March 12, 2014

March 20-24 Potential Storm System

I'm watching out for a potential storm system around the March 20-24 timeframe.


WeatherBell
There is a rule, well explained by Joe Renken, that states a weather phenomenon in East Asia will be reciprocated in the United States 6-10 days later. This means that if there is a storm system in Japan on a certain day, we can expect a storm in the US 6-10 days after that. The same goes for high pressure and warm weather. Using the image above, we can expect a storm in the US 6-10 days after March 14th, which would bring us to a March 20-24 storm. 

The storm looks pretty healthy in this model projection, which could also mean we see some active weather, both in terms of severe and wintry weather. It's still too far out to tell who could get hit, but considering we'll be seeing the Madden-Julian Oscillation in Phase 2 around this timeframe, I would keep an eye out for severe weather.

(The following is copied from the March 4th post)

Paul Roundy
Shown above is a chart of six different types of outgoing long wave radiation (OLR) anomalies. We want to focus on the middle panel of the left-hand side, where it says MJO OLR anomaly on February 16, 2014. On February 16, 2014, we saw negative OLR anomalies just south and east of the subcontinent of India. This location of the -OLR anomalies (which indicate enhanced tropical convection) tells us the Madden-Julian Oscillation was in Phase 2, out of its 8 possible phases. Check out the severe weather event that occurred just four days later, on February 20, 2014.


On February 20, 2014, we saw a large-scale severe weather outbreak, as the chart of storm reports from the Storm Prediction Center shows above. The outbreak was primarily a damaging wind event, as you can see by the large swath of blues across Tennessee and Kentucky, just to name a few of the many affected states. However, we also saw a handful of tornado reports. The fact of the matter is, this severe weather event and the MJO entering Phase 2 are not coincidence. They are correlated with one another. See the AMS (American Meteorological Society) article below:

The Madden–Julian oscillation (MJO) has been linked to weather variability in the midlatitudes via its associated overturning circulations and Rossby wave trains that redistribute the thermal and mass fields at higher latitudes. This work examines the relationship between the MJO and violent tornado outbreaks in the United States. A census of events shows that violent tornado outbreaks during March–April–May (MAM) are more than twice as frequent during phase 2 of the Real-time Multivariate MJO (RMM) index as during other phases or when the MJO was deemed inactive.

If you didn't get what this was saying, don't worry. Basically, it tells us that when the MJO is in Phase 2 during March, April and May, or when we see enhanced convection south and southeast of India, we tend to see the chances of a violent tornado outbreak skyrocket in comparison to the nonactive MJO, or the MJO in other phases. While the February 20th event wasn't exactly a tornado outbreak, it was a severe weather event, and this has me concerned for mid-March.


Let's take a look at the forecasted OLR anomalies for March 12, 2014. Once again, we'll look towards the panel labeled MJO OLR Anomaly. If we look at the forecast by Paul Roundy above, we can see very deep negative OLR anomalies placed just south and southeast of India. These blues are far deeper than what we saw on February 16, meaning that this Phase 2 MJO event could be even stronger, and thus the severe weather event would be even stronger as well. Going by the LRC we discussed above, as well as the AMS document analyzed here, I am concerned that we will see a potentially significant severe weather outbreak for the mid-March period. Because there could be a lag period between the MJO Phase 2 event and the severe weather event of about 4 days, like we saw with the February event, I'll make a tentative timeframe of March 13-18 for a potential severe weather outbreak. This one has me worried, and while you should not be worried yet, it's something to watch out for in the future.

(End copied post)

If we come back to Paul Roundy's forecast and look at the MJO OLR Anomaly panel, it looks like the placement for Phase 2 anomalies has been pushed back to March 16, which would put the possible severe weather threat either just before or during this potential storm system. Lots of things to watch here.

Andrew

March 15-19 Potentially Significant Storm System

I'm eyeing the March 15-19 period for what could be a significant storm system.

The image above shows ECMWF 500mb height anomalies from a previous forecast, valid on March 9th, which was two days ago. While this forecast is not current, and the forecast image above is not current either, we did see a big storm move through Japan on March 9th. There is a rule, well explained by Joe Renken, that states a weather phenomenon in East Asia will be reciprocated in the United States 6-10 days later. This means that if there is a storm system in Japan on a certain day, we can expect a storm in the US 6-10 days after that. The same goes for high pressure and warm weather. Using the image above, we can expect a storm in the US 6-10 days after March 9th, which would bring us to a March 15-19 storm. Not only that, but this forecast indicates the storm in Japan will be/was strong when it passed through, and this means that the storm we experience March 15-19 could very well be strong, too.

Shown above is the latest ECMWF ensemble mean forecast for 500mb height anomalies on the evening of March 15th. Interestingly enough, we see the ECMWF ensembles already have this storm in the Plains, meaning the idea of a big winter storm for this timeframe is becoming popular. The ensembles have a positive PNA pattern in place, meaning we see high pressure shooting north along the West Coast, with consequential storminess in the Plains. We also see ever-so-slight ridging in the Southeast, but this is suppressed by the piece of the polar vortex displaced over southern Canada. It looks like the ensembles want to develop a split jet stream pattern, which could open the door for phasing of storm systems. Despite this potential, I feel that any storm in this timeframe would either move east and possibly up the coast, though I'm a bit hesitant about that potential due to the polar vortex pushing down on the jet stream as well as the storminess over Greenland (which typically does not favor East Coast snowstorms). The other idea would be the storm moving north and hitting the Midwest/Great Lakes, but I'm also skeptical on this idea due to the polar vortex piece trying to suppress the storm (which could very well happen), as well as the lack of high pressure in the Southeast to force the storm north. We'll get a much better handle on this in coming days, but be warned that the March 15-19 period could see a potentially significant storm hit the US.

It is also worth noting that we could see some severe weather, though to which degree is to be determined.

Andrew