Friday, May 26, 2017

Winter 2016 -2017 was warm but also snowy for many of us.

The very strong El Nino of 2015-2016 ended in April of 2016. At this time it was thought that a La Nina would follow for the Fall into the Winter.  The ENSO neutral conditions did turn to a very weak La Nina. But it quickly faded, leading to ENSO neutral heading into the late Fall and Winter, then we quickly started the transition to another El Nino.  This is the first time we've gone from a strong El Nino to a brief neutral/weak La Nina, Back to a developing El Nino.

The problem was it takes the atmosphere awhile to adjust from one state to another. All of this change in such a short time, made things very complicated and unpredictable.

As the winter progressed we saw SSTs climb west of South America in the Tropical Pacific.  The positive EPO kept the pattern transient; the lack of blocking kept winter at bay.

Adding to this problem we had that warm pool of warmer than average SST in the northern Pacific at the start. But, then the SSTs quickly cooled from the Gulf of Alaska and along the coast west of Canada. This had a big impact on the jet stream, keeping the colder air locked up in western Canada, instead of moving into the eastern CONUS.

Another thing that lead to the warm winter of 2016 -2017 was the warmth in the Arctic. This allowed also helped keep much in the way of cold air invading the eastern part of the CONUS, we just didn't have much in the way of arctic air to work with.

The transience last winter made it impossible for cold and wintery conditions to stay and get locked in. The fast jet stream and lack of blocking were just too much. We got cold, saw snow, then it warmed and the snow melted. Those areas, that had no snow cover stayed even warmer.

Here is a look at winter overall temperatures, along with a look at overall temperatures for December, January, and February. They show that the early cold in December, never returned for January and February, leading to one of the warmest winters on record.







Winter overall


The main complaint I've seen directed at me, was the lack of snow in the Northeast.  But there is where the problem starts. It might be hard to believe, but much of New York, New England, into Pennsylvania saw above average snowfall last winter.  The area that saw substantially below average snowfall was the Mid Atlantic.

Here is a map showing how last winter turned out snowfall wise. I've also included a chart that shows total snowfall for eastern cities.

My temperature outlook for Winter 2016-2017 was a complete bust overall. But my snowfall outlook came in very close to what ended up falling.

The pattern that interfered with last winter, is the same pattern that is causing all the issues with spring 2017.

Forecasting weather is difficult, even in the short term. But to try and look out 4-6 months into the future is near impossible. A seasonal outlook, paints with a broad brush and is a bit vague when it comes to some of the details. The only tools I have are teleconnections, climatology, and analogs. I try to fill in the blank spots the best I can. Most of the time my seasonal outlooks are very good and end up close to the way things go down. But like the winter of 2016-2017 outlook they don't all the time.  Comparing my outlook for last winter to the other outlooks from major outlets, mine ended up better than most. One other thing, the Northeast is a very large area, so there will always be winners and losers when it comes to overall conditions.

I've made a couple of post on why last winter went the way it did..... you can check them out.          

Thursday, May 25, 2017

What a difference a year makes:

Last Summer, into December was dry across the Northeast and Mid Atlantic. Here are a few images from U.S. Drought Monitor for 2016, that show how dry we were.


The last 60-90 days has been wet across the eastern half of the CONUS.
From WeatherBELL 

Our drought in the Northeast has been erased. It has been replaced with well above average precipitation this Spring.


Soil Moisture chart shows just how wet we are now compared to May of 2016.


From WeatherBELL

The next 2-3 months look to be a bit wet. Now given the landfall possibilities I out laid in my hurricane outlook. The Northeast could end up with a tropical system bringing a lot of rainfall. So there is a chance we could be very wet by this Fall.

Climate Prediction Center:

Bit of house cleaning:

I've been asked many times, why don't I refer to or show the CPC three month temperature and precipitation forecast outlooks?

My answer is they are not a true forecast. Instead they are based on a percentage of the odds of probabilities. They are rated on an A,B,C score.  A is above average, B is near normal and C is Below normal. With EC meaning equal chance. For example

Forecast probability anomalies OF 20%, 30% and 40% for above normal

imply probabilities for all three classes (above, near, below)OF 53.3% - 33.3% - 13.3% --- 63.3% - 33.3% - 3.3% AND 73.3% - 23.3% - 3.3% respectively.


Here is the current CPC three month outlook for temperature and precipitation.


Here is the chart I did for my summer outlook. This is an actual forecast that can be verified.


Anyway back to my post.  


I've been saying for months, that this Summer will be a lot cooler than last Summer. I've been saying average to slightly above average for temperatures. Looking at some of the models we can see they are calling for the summer to be cool.


The next 6 weeks are forecast cooler on average in the EPS.

From WeatherBELL

The CFS latest run has the nation cool.


From WeatherBELL

We have a + Atlantic Multidecadal Oscillation (AMO) and a + Pacific Decadal Oscillation (PDO), this would explain at least in part, why the Spring has been behaving like it has.
The +AMO would also help account for the active severe season this year. There seems to be a linkage that shows an increase in the frequency of tornado outbreaks, when we have a +AMO. There is also some evidence that suggest + AMO leads to greater numbers of tornadoes associated with landfalling tropical cyclones.    

The Teleconnections are at odds on the ENSO. Many are backing off from the chance for El Nino developing.

From Tropical Tidbits.

Looking at the surface temperature anomalies  you can see how much colder (relative to average) the Central to Northeastern CONUS has been.

Since the first of the year, Sea Surface Temperature Anomalies (SSTAs) have warmed in the eastern tropical pacific, but cooled off in the Gulf Of Mexico ( GOM) and western Pacific and  the central Atlantic.  While the northern Atlantic and southern Pacific Ocean have warmed.

My estimate of the daily Nino 3.4 index is +0.7 which is a El Nino index Value. On the other hand, NOAA has the weekly Nino 3.4 at +0.4, a neutral value.


I still believe we're going to see a weak El Nino Modoki (central based), or negatively based ENSO, this Fall going into the coming winter. If we do see a weak La Nina it would be east Based.  If I'm right, we're going to see an active and cold winter for 2017-2018.

This is how things have gone so far, and where things look to head for the next three months.

Well that's about it.