Friday, September 4, 2015

Pattern Change Imminent for North America

Welcome back to The Weather Centre! We are now resuming winter weather posting, which means we're back in business for the next several months! We're kicking off this winter with a pattern change update for North America.

It is expected that a pattern change will impact the United States in the next week or two, leading to substantial air mass shifts across North America.

ESRL
Over the past week or so, we've seen a persistent, high-amplitude weather pattern over the Northern Hemisphere, particularly in the North Pacific. Deep negative height anomalies have been situated west of the Aleutian Islands, as well as along the coast of western Canada. A strong ridge has maintained position over the Aleutian Islands and across the Bering Sea. This volatile pattern has wedged the United States into a rather stagnant pattern, with warm weather over-spreading the Central United States, making pushes north and east as time has gone on.

This pattern is about to change, as we see two main playmakers rile up the atmosphere.

Tropical Tidbits
The first will be the shifting of that deep trough along the west coast of Canada south into California, and then moving north and east into Montana, as this GFS Ensemble forecast shows on the morning of this coming Sunday. Locally, this means warm weather continues for the Plains, with that ridge still not budging, as well as warmer weather in the Midwest and Northeast. However, as that trough moves eastward, we will start to see the jet stream become more zonal.

Tropical Tidbits
By Wednesday morning, we see significant changes to our atmospheric mid-levels. We now see a dominant zonal flow of the jet stream, as the smoothness of height contours over North America shows. Some slight ridging remains in place along the East Coast in the United States, but this too will be shunted away in due time, as the zonal flow is maintained by the strong storm system in the immediate vicinity of Greenland (some of you more knowledgeable weather enthusiasts may recognize this as a pattern similar to that of a +NAO wintertime pattern).

Tropical Tidbits
By Friday morning, a week from this post's publishing, we see a complete flip in the pattern from where we are currently. Strong ridging has taken over along the western coastline of North America, maximized in the Pacific Northwest into the British Columbia region. In response, similar to a +PNA pattern in the winter, we see cooler, stormier weather working its way into the Central US and East US. A note for any severe weather fanatics still watching the fall tornado season threat, I wouldn't be surprised to see some storms anywhere from Oklahoma to the North Plains under this northwest flow.

There is another factor that we will have to watch in the next couple weeks, and that is tropical storm Ignacio.

RAL/UCAR
Ignacio is currently located in the middle of the Pacific, due south of the westernmost Aleutian Islands. The image above shows forecasted storm tracks from all available GFS Ensemble members. The consensus among these members, as well as other statistical forecasting models, is to have Ignacio curve north and east, making another 'landfall' as a post-tropical system in British Columbia. From there, already-low confidence gets significantly lower, as ensemble tracks take this storm anywhere from the Arctic Circle vicinity (as shown by member AP17), or the Lake Michigan region (as per members AP10, 12, and 14).

As far as impacts, we can split it up into a number of talking points. For one, this will drastically lower forecast model skill over the next two weeks. While it isn't necessarily uncommon for post-tropical systems to make their way into the mid-latitudes, forecast models almost always see a drop in verification due to this occurrence. Therefore, long-range forecasts over the next several weeks are subject to anomalously worse verification rates.
Secondly, as Ignacio was once a Category 4 hurricane, we could see a strong storm system develop over land here in North America. Local impacts may include substantial rainfall, possibly to the point of severe weather potential, but that all depends on where the storm tracks, and if it even makes it to North America to begin with.

To summarize:

- A pattern change will unfold across North America over the next 7-14 days.
- A heat wave will impact the East US, to be replaced by cooler weather about a week from today.
- Post-tropical Ignacio will hinder forecast model accuracy, and may also bring about anomalous weather conditions in the U.S. in the next 10-20 days.
- Cooler weather will prevail in the Central US in the next 7-14 days.

Andrew

Saturday, July 25, 2015

Preliminary 2015-2016 Winter Forecast

Hello everyone, and welcome to The Weather Centre's Preliminary 2015-2016 Winter Forecast. As always, the standard caveats of very-long range forecasts apply here; in other words, do not take this at face value. Rather, this should be interpreted as an introduction to the conditions that are probable in the coming winter, which will be built on in coming months.
As a note, this outlook will be far shorter than previous seasonal outlooks. This comes from a combination of items, which have significantly restrained my time available to work on this. However, I'm committed to putting out this product, as I have been advertising.

We will begin with a look at the sea surface temperature picture across the world.

ESRL
Glancing around the globe, we see a few points of interest.

1) We do have a Moderate to Strong El Nino coming on, continuing to manifest itself in well-above-normal SST anomalies off the western coast of Ecuador, well into the central Pacific. These El Nino's tend to result in warmer than normal temperatures in the North US, cooler than normal temperatures in the South US, as well as stormy conditions in the South and East US.

2) The warm pool continues to persist in the Gulf of Alaska and entire Northeast Pacific region. This is the same warm pool that brought us severe cold in the last two winters, through the abundance of ridging along the West Coast. If this warm pool is to persist into the coming fall and winter, the threat of a third consecutive cold winter skyrockets, especially given the warm pool's geographic location immediately upstream of North America, maximizing its effects.

3) There are below-normal SST anomalies around the island nation of Japan. The Typhoon Rule states that storms and high pressure systems that occur over Japan are 'replicated' in the US about 6-10 days later. The Sea of Japan experiencing below-normal SST anomalies could hint at a stormier than normal weather pattern for that area, which could spell a stormy winter if it continues into the fall and winter.

I will not be discussing the QBO or sunspot factors in this outlook. If this were a normal outlook, I certainly would, but there are things out of my control that have simply made the prospect of such an extensive outlook unattainable. I apologize for the inconvenience, and hope you can understand.
In spite of these time constraints, I have been glancing at long range models and some other seasonal factors, so I could come up with my preliminary thoughts on the coming winter.

CONCLUSION

Pacific Northwest: Very much a toss-up. Warm pool in Gulf of Alaska could spell a hot and dry summer, while the El Nino could bring about more wet conditions. I'll lean towards a warmer and slightly drier than normal Pacific Northwest this winter, with low confidence.

Southwest: Expecting a cooler than normal and slightly wetter than normal winter, as a result of the expected strong El Nino. Have to keep an eye out for interference from that warm pool in the Gulf of Alaska, which could dry things out yet again. Once again, a low confidence forecast.

North Plains and Midwest: A Strong El Nino predicts a warm winter ahead, but I'm not completely convinced so long as the body of warm water exists in the Northeast Pacific. Still, a slightly dry, slightly warm winter is my best projection for now.

South Plains and Gulf Coast: Decent probability of cooler than normal to average temperature pattern for the winter, along with some stormier than normal activity.

Southeast: Difficult forecast for this region, as the El Nino could result in a very wet and cool winter. However, there are other variables which significantly complicate this region's forecast, namely the Atlantic Multidecadal Oscillation, which I'm not prepared to discuss due to very low confidence. I'll side with a wet and cool winter for now.

Ohio Valley: Early projections do favor a slightly warm, slightly dry winter, and for now I agree. This is one of the less complicated forecasts (for now).

Northeast and Mid-Atlantic: This certainly has the potential to be a 'feast or famine' winter for the Northeast, in terms of snow. I do think we see around average temperatures for the winter, but I'll go ahead and favor a snowier than normal winter.

Andrew

Saturday, July 4, 2015

Long Range Lookout: Cooler Than Normal July Ahead

This post is dedicated to the servicemen and women who are serving our country, who have served our country, and those who have made the ultimate sacrifice for our country.

It appears that a cooler than normal July is on the way for the nation.

We'll begin by looking over shorter-range indicators; in this case, the Typhoon Rule.

Tropical Tidbits
The above image shows forecasted 500 millibar anomalies over the West Pacific. Here, blues indicate negative height anomalies, symbolizing a trough or storm system in the area. Oranges and reds correlate to positive height anomalies, indicative of warmer and quieter weather.
This forecast is valid for July 14th, and we see a system just southeast of Japan, making its way north and east. This system was previously a typhoon, which looks to develop in coming days further to the south. As the typhoon approaches Japan, it will curve and head out to sea. Using the Typhoon Rule, we can expect a cooler bout of weather about 6-10 days after this happens. Recognizing that this forecast is for July 14th, we can extrapolate that to forecast a cool-down around July 20th to 24th, probably spilling over those dates a bit.

However, it's also likely that the entire month will end up cooler than normal for many in the country, due to what is happening in the Central Pacific.

BOM
A quick overview of the columns, going from left to right: The date for the data, the daily barometric pressure reading in Tahiti, the daily barometric pressure reading in Darwin, the daily value of the Southern Oscillation Index (SOI), the 30 day averaged SOI, and the 90 day averaged SOI.
In a nutshell, when the SOI is negative, El Nino conditions are favored in the United States in the following couple of weeks. We see that the SOI has been consistently negative since June 19th, and it's no coincidence that the United States has been predominantly cool since late June.
You can see how El Nino conditions, which are signaled by a negative SOI, make for a cooler than normal summer in the composite chart below:

ESRL
Typical temperature anomalies during an El Nino summer
Since we remain in a negative SOI state this 4th of July, I'm expecting the rest of the month to end up cooler than normal for much of the country. Those in the Southeast and East could see slightly warmer conditions, however.

To summarize:

- A cooler than normal month of July is expected for much of the United States.

Andrew

Sunday, June 14, 2015

An Announcement Concerning The Future of The Weather Centre

It's only been a month and a half since I signed off from here, but it seems like a while longer, no?

Since I ended The Weather Centre on our five-year anniversary of its foundation, April 26th, 2015, I've had some time to reflect, and do some work.

I've been able to take a breath, push back the keyboard, and re-energize myself after a very long five years of work. The first week or two of being away from the blog gave me a break unlike that I had experienced over the last several years.
However, particularly over the last couple of weeks, I've found myself hit at night (every other day, seemingly) with an incredible urge that I have to do something related to meteorology, in order to feel accomplished in my endeavors. I've already wrapped up my tornado research, so I've had to resort to long hours staring at my computer, never really getting much done, but still feeling that burning desire to actually accomplish something.

Then, a few days ago, someone told me that perhaps that burning desire had come about because I had stopped blogging. At first, it seemed somewhat absurd, since my tornado research needed attending to. But now that I've had time to think it over, it really does seem that posting my thoughts about the weather puts my mind at ease; the very mind I wished to put at ease when I ceased posting on this blog.

So, to confirm what some of you have been discussing over the last couple of days...


I am coming back to The Weather Centre.


This 'return' of sorts will come with a markedly different posting regimen, which I will break down below.

The articles listed below will be published:
- Over the next few weeks, I will publish my Preliminary 2015-2016 Winter Forecast. I will announce a publication date in coming days, but as I've always done, you can expect it to be at high noon on a Saturday.
- I will publish an Official 2015-2016 Winter Forecast further down the road.
- I will publish extended discussions on winter storm systems, cold air outbreaks, and other winter phenomena.

Changes will be made to the following types of articles:
- There will be severely limited, if not non-existent postings during the late spring through middle of summer.
- Severe weather and tropical cyclone postings are not anticipated, unless threatening a large portion of the U.S.

Basically, I'm trying to say that I'm coming back to The Weather Centre just to discuss what I love, which is winter weather. I don't plan on making attempts to post in the spring and summer, since I firmly believe that is what drove me to initially stop posting.
Additionally, please do not interpret this as just another ploy to mess with your emotions, given that I had already announced my 'retirement' from this blog. I take this announcement very seriously, and I hope you're still willing to hang on for the ride this coming winter.

Stay tuned for additional information and postings in coming days.

Andrew

Sunday, April 26, 2015

A Final Farewell

(For some context, please read the most recent post, A Final Notice to the Viewers).

On April 15th, I made a decision to move from one stage of my life to the next, by announcing that I would be ceasing operations here at The Weather Centre on our five-year-anniversary, April 26th 2015. In that process, I finally lifted the veil over my age, my (lack of) credentials, and how I got started on this blog in the first place.

The response I got was very much the most overwhelming and inspiring collection of comments I have ever seen anywhere on the Internet, and possibly at any time in my life. As I read and re-read your comments, I started to really realize what The Weather Centre has become. It is not a blog; we've built it into a community unlike any other. For five years, we all contributed to teaching each other (myself included) a little more about the weather with each post, and that's something I'm extremely proud of.

As I sit here, writing what will be the final post on The Weather Centre blog, I'm experiencing a wide range of emotions. I can still remember the feverish nights spent during the April 2011 tornado outbreak, posting tornado warnings on this blog, not being able to keep up with all the warnings that kept coming out. I can still remember rushing home from school on a daily basis to check the weather models and whip up a new post on an impending winter storm. But the thing I remember most is how fun it's been, and how sad I am to see it go. However, as the saying goes:

"Don't cry because it's over, smile because it happened."
- Dr. Seuss


As I close the book on this chapter of my life and move on to a new one, I can't help but smile.

Thank you all for such an incredible five years. This has become something more than I could have imagined in my wildest dreams, and you've all been the driving force behind it. There is nothing else I can say but thank you.

For the final time,
Andrew Racki