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At least 10 people were killed as tornadoes ravaged parts of Mississippi, Louisiana, Arkansas and Alabama on Saturday, April 24th. Rescue crews are still searching for missing people as the damage paths were wide and the wind speeds had to be over 200 mph in the stronger tornadoes. Yazoo City, Mississippi was the hardest hit town.
This storm system that produced the severe weather outbreak is related to others we have had this season as a major stormy part of this years LRC. I will go into more details this week.
Gary
Good morning and welcome to LRCWeather.com,
In recent blog entries we have been going over the cycling weather pattern and wondering what it means for severe weather season in the weeks ahead. Lezak's Recurring Cycle (LRC) has been repeating since it set up last October. It has a period of around 55 to 65 days and we are in the fourth cycle of this year's pattern right now. For those of you new to the LRC, we believe that a unique weather pattern sets up every year between October 1st and November 10th. A new cycle length evolves and the pattern repeats through fall, winter, spring, and through the first half of summer before a slow evolution into next years pattern begins. So, we believe that the weather pattern that is now moving into late April and May is still directly related to the pattern that set up last fall and brought so many record breaking winter weather events to various parts of the nation. Now, what will this weather pattern mean for severe weather season?
There is a very good chance that severe weather season will become alive and kicking within the next two weeks. Let's take a look at where we are right now and open up you mind to the comparison I am about to show you. This will be just a snapshot in time, one day in each cycle. It isn't just one day or one week, but the entire weather pattern that is cycling over the Northern Hemisphere. We use the 500 mb level to show the comparison, but there are many other ways to do it as well. The 500 mb level is halfway through the atmposhpere in weight and a great level to show the cycling river of air above the surface.
Take a look at the forecast map valid 1 PM Tuesday, April 20th. I am picking out five features to compare to other cycles:
Feature #1 is a weak wave devloping on the east side of a high amplitude ridge, feature #2. It is dropping south southeast through the plains states and it may be able to produce a band of showers and thunderstorms. Feature #3 shows some strong energy diving southeast under a blocking ridge that is developing over Canada. Feature #4 shows a couple of upper level lows under a blocking ridge, feature #5.
Now, let's compare these features to the next two maps remembering that in each cycle there are seasonal differences in the amount of energy in the flow. The April version shows weakening upper level flow, while the December version of the LRC characterizes a strengthening jet stream and upper level flow, and the February version shows the upper level flow just after peak strength is reached. These seasonal differences, and possibly many other factors, will sometimes masque the pattern, but if you follow it as closely as we do then you can see that it is really all the "same", but just a different version.
In the February version of this pattern, Valentines Day, a very strong wave was dropping south over feature #2 into the central plains. It produced very heavy snow showers, despite very little available moisture in Kansas City. There was a 40 car pile-up on I-70 that afternoon as this wave moved through. Feature #3, instead of diving south under the high amplitude ridge, is just nudging the ridge east and being deflected over the block. Features #4 and #5 may seem a bit different, but this is just a seasonal difference. They are still there!
And now, here is the pattern from the second cycle of this year's LRC. Again, you can see the wave moving southeast through the central plains, feature #1, and it is dropping south in response to the high amplitude ridge, feature #2. Feature #3, like in cycle three, is nudging the ridge east and being deflected over the top instead of diving under like what we are seeing this week. Features #4 and 5 compare well with the other cycles.
So, what can we take from this one comparison of the cycles? Can we use this to look ahead and forecast severe weather season in late April and May? Yes! But, it is always quite challenging for many reasons. What will the much weaker May and June versions of this years unique weather pattern look like? There are no analogs that so many meteorologists like to look at, as this is unique. So, we must use our forecasting ability to look ahead and project what may happen. The LRC Weather Team has been highly successful in recent years at making these forecasts. Here is one forecast that was published on the KC Confidential website on this link: www.kcconfidential.com/?tag=kshb-tv
“I predicted (Monday) that between now and the end of March we will be hit by multiple snowstorms based on my LRC theory,” Lezak says. “I am predicting we will have 18 more inches of snow and that’s a lot of snow considering we’ve already had 23 inches. That will put us up to 41 and 65, I think, is the record. The only way we’ll get close to that is if we get absolutely blasted by two of these snowstorms and that’s not out of the question. So we’re about halfway through the snow this season.”
What happened? 18 more inches did fall through the entire Kansas City viewing area. KCI Airport ended up having 21 more inches of snow ending with 44 inches for the season. It wasn't just a lucky forecast. We have many others we could post here, but I will save it for my presentation that I am making on the LRC at the Broadcast American Meteorological Society Conference in June.
Now, what can we expect in the weeks ahead? There was a major storm in cycles 1, 2, and 3 within a week to ten days after this part of the pattern. A major storm in late April has to lead to some significant severe weather somewhere. There should be some good chances setting up soon for storm chasing, but this is still a strange and unique weather pattern. We will go into more specifics on the Action Weather Blog at www.NBCActionNews.com. Just click on the weather blog over there in the coming days. Kansas City weather enthusiasts will remember the February snowstorm and the Christmas Blizzard, both predicted weeks ahead of time based on the LRC. Let's see what happens in cycle 4.
Gary Lezak
Happy Tax Day LRC Weather bloggers,
I just went over the last six months of 500 mb charts from cycle 1 through today. The LRC (Lezak's Recurring Cycle) set up last October and I don't think anyone will debate that it has been a unique weather pattern. Something fascinating started happening in early October and evolved into a weather pattern that produced record seasonal snowfalls in many eastern cities, and near record seasonal snowfall totals near Kansas City. It was a pattern that was relentlessly cold in the central plains. Kansas City went months below 60 degrees and over 200 days below 80 degrees.
This same weather pattern is cycling today and as winter's last gasps will produce some late season snows over the higher elevations of the western states and possibly some northern tier states, there has been a sudden warm up across much of the nation. But, this may be short lived.
As Jeff Penner and I were looking at the last few months of data we were just amazed at the unique characteristics to this year's pattern that may never return again. There has been so much splitting and blocking with the AO in the negative for much of the season, and going more negative again as I am writing this.
But, what does this mean for the weeks and months ahead as the LRC fades slowly as summer approaches. The flow aloft will weaken? The cycling pattern will continue until there is a transition into next year's LRC. I still think it will get quite wet in the plains as spring moves into late April, May, and June. How significant will the potential flooding become? Where will the first heat wave set up? How will this affect the corn and soybean crop? Will there be planting delays?
Severe weather season has really been quiet so far. There is a very good chance that it will become much more active before the end of April. And, we will go into more details soon.
Gary
Greetings bloggers!
I apologize for not blogging as frequently as I had in the last year or so, but things have been very busy on the business end and that is my priority with the company. More and more businesses are seeing the value of the LRC for forecasts and we have been picking up steam on providing accurate forecasts for these clients. There is a difference. A huge difference in using the LRC. Ok, so what is this blog about?
The tropics.
It is never to early to think tropical. My atmospheric research started with a tropical focus so I have an affinity in keeping an eye on it leading up to and during hurricane season. Also, in light of the brutally cold winter for many - warmer thoughts are in order.
Recently, I have seen several tropical forecasts put out. I have read Dr. Gray with Colorado State and Joe Bastardi with Accuweather. I am not sure I fully agree with either, but do agree on some points. I will lay out the points I factor in analysis, what I am thinking and summarize with what I think will happen.
There are many factors to consider and this year is a bit trickier than others. Last year I fared rather well using a heavily weighted LRC forecast, and this year will also use the LRC, but blend in a few other of the more standard factors. I found the LRC last year to be especially useful in what was otherwise a mean ENSO tropical season.
For this forecast and analysis, I am going to stick to the Atlantic side of things. Because of the threat to the mainland US, it is more interesting to me. If anyone is needing a Pacific forecast, shoot me an email at biz at lrcweather dot com.
Without further ado, lets get to the factors I used for the forecast:
La Nina/El Nino [ENSO] - Sea Surface Temperatures [SST] - Wind Anomalies - Madden Julian Oscillation [MJO] - Teleconnections - Saharan Dust, and last, but certainly not least...the Lezak's Recurring Cycle theory [LRC].
Let's start with the ENSO:
After a nice run of El Nino conditions, it is fading and heading to ENSO neutral conditions. It looks to do so by the beginning of the typical time frame for development from July through November.
With a declining El Nino signal, it could enhance the tropical Atlantic initialization by reducing wind shear allowing for easier development. Typically El Nino conditions during the hurricane season yield less hurricanes than neutral or La Nina. In addition, I did consider several past analogs of this year's ENSO pattern. It would suggest a higher than normal amount of tropical development.
SST - Looking at the current SST anomalies, the Gulf is a bit cool and the eastern Atlantic is a bit warm. I expect this trend to largely continue with the Gulf staying normal to a bit cool and the eastern Atlantic to remain warm. This should encourage the Cape Verde development and delay Gulf cyclogenesis until a bit later in the season. Not unusual, but may be a bit more difficult to sustain intensity through the Gulf should something get there until later in the season.
Wind - with the dying El Nino and the largely persistent negative NAO this year, wind should be favorable in the Atlantic. I will talk more about the NAO here is a second. With wind anomalies being neutral or favorable, this would improve chances of development with less shear to tear apart the storms in their formative development stages.
Teleconnections - Both the MJO and NAO would fit here, but I will focus on the NAO and give the MJO its own consideration. The NAO this year is very telling. Looking back through late fall, the NAO has been largely negative and I expect it to continue. This lends to several considerations as it pertains to the conditions in the Atlantic. First, with it being negative, westerly surface winds across the Atlantic will be weaker. This too will aid in the favorable shear conditions. Second, it may lend a higher likelihood for land falling hurricanes due to steering currents with negative AO large scale patterns. I will leave the other teleconnections alone as the NAO is the most directly relating teleconnection due to its proximity.
MJO - The MJO can have quite an impact on the environment in the Atlantic for tropical convection and cyclogenesis.
The MJO produces a strong modulation of tropical cyclone activity in many regions of the tropics, including the Atlantic Ocean, Gulf of Mexico, and east Pacific Ocean. The MJO is associated with variations in sea surface temperature, organized precipitation, low-level winds, vertical wind shear, and atmospheric humidity and temperature, important factors in tropical cyclone formation and maintenance
Looking at the MJO trends this year, looking at the last ~180 days, the mean phase has been about 4.6. Based on how this phase pattern looks and the associated enhancement/suppression of convection across the equator, this mean is favorable for development in the equatorial Atlantic for convective development. Now - realize, the MJO is a cycling oscillation, so there will be unfavorable times as well, but each year's oscillation is somewhat unique and will have tendencies to favor certain parts of the convective trends in its path through the equatorial regions. I will stop here without getting much more into the mechanics of the MJO.
Saharan Dust - Looking at the current conditions in Western Africa, it is a bit dry. This could enhance African dust plumes in the Cape Verde region.
As dust is lifted from the surface and brought into the area near the Cape Verde islands and beyond, this dry air can choke out development of storms that would otherwise form with the warm water. It is something to watch.
LRC - This year's pattern has favored a few different regimes. One that is starting to really take hold now in this part of the pattern is the amplitude of the southeast US high pressure. It seems to retrograde somewhat westward linking to anomalous heights in the polar region. While I don't think this is a constant feature, it will have an impact. Also, we have seen quite a split flow regime this winter with the strong sub-tropical jet. I don't favor this pattern being strong into the late Spring into Summer. With the seasonal de-amplification of the subtropical jet and the retreating El Nino, this part of the pattern should begin to weaken and may yield more ridging without mid level waves undercutting through the subtropical jet.
So, with all this said, what does it mean?
In looking at this, I would think odds of a more active season than last year is a near certainty. I do favor a near normal to a tick above normal tropical season. I am not as aggressive as some on the forecasted increase in activity, but I do favor a higher than normal season. I think the Cape Verde storms will be dominant. I think the SE US high will be a major player in steering storms. It may aid in protecting Florida when it is active in the pattern and push storms into the Gulf. With the Gulf being cool in the season, this would be good as it would help reduce the intensity of these storms prior to any possible landfall. Later in the season, it may not help and may even increase intensity if the Gulf is left largely undisturbed early in the season and will have benefited from increased SST from central/southeastern US ridging.
I do think there will be 2-3 US landfalls this year and think probably two in the Gulf and one along the East Coast - perhaps along the Carolina coast. I think there is a higher than average chance of one of these being a major hurricane at land fall.
So - here is the probability I see right now. Below normal season - 20% Normal season - 40% Above normal season - 40%
Here is the caveat - this is just my thoughts as I see things right now. Things can and do change and it is possible with a forecast this early. I am not big on making frequent updates to forecasts and prefer to stick to my first thoughts. If something dramatically changes, I will make an update.
What do you think? Have a great day!
Scott
