Thursday, March 21, 2013

Spring 2013 outlook part two.

OK here is part two to the Spring outlook for 2013. As with any seasonal outlook it looks at the overall setup, then tries to give a broad spectrum analyses, to anticipate what the season will be like. What it doesn't do, is give any details on individual storms or events.

Part one of the outlook dealt with the temperature outlook for Spring 2013. Part two will deal with precipitation/drought and severe/tornadoes.

Part one can be found here. 

Drought/ precipitation:

As most of us are aware, the weather pattern for this March is immensely different than last March. It was the same for Winter 2012-2013 when compared to Winter 2011-2012. While first half of Winter 2012-2013 was mild; the second half was anything but, the warm snaps gave way to waves of cold moving out of Canada. The pattern was very active with coastal storm after coastal storm hitting the region, resulting in most areas in the Northeast seeing average to above average snowfall.

With this year's average to above average snowfall for the vast majority of us; the Northeast has reversed the drought conditions from last year.

The snowpack will translate to a more favorable environment during the growing season for agriculture in most areas across the Northeast.

For the nation's midsection the picture is not so bright. The Heartland is enduring the worst U.S. drought since the Great Dust Bowl of the 1930's. So while recent rain and snowstorms across the Plains was welcomed with open arms; The impact will be fleeting. 

Unfortunately, the National Oceanic and Atmospheric Administration (NOAA) April, May, June precipitation forecast indicates equal chance of either above or below normal moisture, but a better chance for greater than average temperatures. All this would do is aid in increasing dryness of the soil in the Midwest and Southern Plains.

 But as I said, the outlook is much better for the Northeast. Because of the cold hanging around longer, we will see lower soil temperatures which will cause lower evaporation rates. Also there will be less danger of cold snaps that would kill budding, which was not the case last year. Last year many of us loss plants in the garden. Also the trees budded very early, only to lose them to a cold snap, which put stress on the trees in the Northeast.


    off01_prcp

NOAA precipitation outlook for Spring 2013


  off01_temp  
NOAA temperature outlook for Spring 2013  

If you look at the chart you will see MA, VT, NH, and ME along with the rest of the region, are labeled EC, which means the Northeast has as much of a chance to see above average precipitation, as it does below average. But I think, the Northeast should see average precipitation This combined with the deep snowpack will allow for much more available water for personal, agriculturally, and recreationally. This should keep this year's Northeast fire weather outlook under control.


    nsm_depth_2013032105_Northeast

The amount of snow in the higher elevations is shown here.

    nsm_swe_2013032105_Northeast
The snow/water equivalent is shown here  

Of course snow has to melt. As you can see the Tug Hill, Adirondacks, and White and Green mountains have a lot of snow. So what about the flood outlook?  Right now it looks like the potential for flooding due to snow melt is near normal. But it is pushing the high end across the Tug Hill and Mountains.
 
The amount of snow water equivalent shown on the map is about normal. Also, there are a few ice jams across the region. But right now they don't pose a hazard. However, the current pattern is quite active, with the cold air hanging on into April. Any snowstorms that do occur could tip the balance. So things will have to be watched.  

Severe/tornado:  
 
The average number of tornadoes per year in the U.S. is around 1,300, according to the Storm Prediction Center.  
 
The unusually quiet tornado season of 2012 was a complete reversal of record breaking tornado season of 2011. Last year the tornado season was very active in December into March We saw the record breaking Christmas outbreak. January saw another very large outbreak. But that ended just after April 14. On April 14,2012 we saw a major tornadic outbreak, which included dozens of tornadoes in Kansas. But, going into the rest of Spring and the Sumer tornado activity fell off sharply; by year's end, there were fewer tornadoes than ever on record.  
 
Tornado season varies with region. The tornado season tends to move northward from late winter to mid-summer. The deep south and down toward Florida getting their season in late fall to early Spring. In the Southern Plains, it lasts from May to early June. And in the Northern Plains, upper Midwest, and Ohio River Valley April through June, For the Northeast peak season is in last part of May into August. Tornadoes are most common in general from the months of April through June.  
 
If you follow my Facebook weather page, you know I talk about the Tornado and Dixie Alleys. But in-case you don't know where those are:  
 
Tornado Alley refers an area on the Plains going north to south that covers the northern region of Texas, Oklahoma, Kansas, Nebraska, Iowa, the eastern edge of Colorado, southwest tip of South Dakota and the southern edge of Minnesota.
 
 In the Gulf Coast region, Dixie Alley refers to West Tennessee, West Kentucky, North Mississippi and North Alabama.
  
A post I did in 2011 goes into detail on tornadoes and how they form. It can be found here.  
 
This Season:  
 
Severe weather season this year will be different from last year, ENSO neutral conditions tend to favor slightly above-normal severe weather in the Midwest and South. We can expect more damaging wind events, like derechoes. The long-range models are showing that a more prominent low-level flow of moisture will be present from the Gulf, feeding the complexes farther north over the Plains. This could aid in the formation of tornadic supercells.  
 
Once we get into April we should see severe weather over the lower Mississippi and Tennessee valleys.

The northwest flow over the Pacific Northwest and California, will continue. This should bring the storms further south, which should cause severe weather for Arkansas, Texas, Oklahoma, Missouri, Tennessee, Mississippi, and Alabama.  
 
Later in the season, severe storms could impact Ohio, Kentucky, parts of Indiana, and Illinois.  
 
This type of pattern favors seasons like 2010, 1974, and 2011. But, I don't think we will see the number of tornadoes we saw in 2010 or 2011  
 
The wild card is the ongoing drought. if it gets a lot worse this year. The dry air would reduce moisture and we would see a stronger then average cap over Tornado Alley........this would sharply cut into the number of supercells.  
 
So based on all of this I believe the number of tornadoes will be above average this season. However, it won't be record breaking.

  ann-avg-torn1991-2010 [Converted]

Annual number of tornadoes by state  
 
The average number of tornadoes in the Northeast is 35-40; the vast majority of these occur in New York State and Pennsylvania.
 
The last few years have seen an uptick in the tornado count across Pennsylvania and New York. However, this year we should see more of an average season severe/tornado wise.  
 
Here is another post I did on severe weather safety. It can be found here.  
 
I have several post that deal with severe weather if you get a chance check them out.  
 
Well that's my Spring outlook…………Hope you enjoyed reading it.  


Rebecca




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