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Strong La Nina Behind The Rough Winter And Spring In The Central!

By Joe D'Aleo
Monday, July 7, 2008

We all have seen how ENSO controls global climate patterns. The strength of the ENSO events both El Nino and La Nina determine how persistent these patterns are.

 

 

Strong El Ninos and La Ninas produce the greatest anomalies, in part because they tend to cause patterns to persist to a large degree. In an average, weak non ENSO (La Nada), there is enough week-to-week and month-to-month variability to allow warm to better balance cold and wet dry. In strong ENSOs, the patterns get “stuck”, so the wet areas stay wet, dry areas dry, cold areas cold, warm areas warm and anomalies build and persist.

 

In a Dr. Dewpoint story a few months back, we noted with La Ninas, you can expect more winter cold and snow across the north, more spring flooding in the central, more tornadoes in the central, fires in Florida in spring and more east coast hurricanes.  All but the hurricanes so far have verified during this past strong La Nina and the peak hurricane season is still ahead of us. Last week we did a story on the Great Hurricane of ’38, one such La Nina hurricane.

 

WINTER COLD AND SNOW

 

The persistent storm track this past winter dropping down into the Northwest crossing the central Rockies then moving through the central into New England resulted in ALL-TIME record snows in many locations from Oregon, Washington and Colorado to Iowa, Wisconsin, Michigan, Ohio, Vermont, New Hampshire and Maine and many southern Canadian cities. We talked about this in our first installment of the What’s New This Week.

 

Take for example Madison, Wisconsin which received an all-time record 101.4 inches, exceeding the old record set in the memorable winter of 1978/79 by 25.3 inches.

 

Rank

Total

Season

1

101.4

2007-08

2

76.1

1978-79

3

75.9

1885-86

4

73.7

1993-94

5

72.4

1985-86

6

71.2

1992-93

7

70.9

1909-10

8

70.7

1897-98

9

67.4

1970-71

10

67.3

1958-59

 

 
Even higher amounts were reported in some areas to the east closer to Lake Michigan (over 120 inches!).
 

 

SPRING RAINS AND FLOODING

With the steady stream of storms continuing but the days growing longer, snow gave way to rain and severe weather in the spring. Iowa turned in the 8th wettest spring and Wisconsin the 12th wettest. For the whole United States spring was the 27th coldest and 40th wettest, that being so even with California stuck in a dry rut, having the driest spring on record. The rains helped kick off the flooding which this month created havoc in several states.

 

SUMMER STARTS WET AND STORMY

 

Summer has started wet, Madison, set the record for the wettest June on record with 10.93 inches to date breaking the record set in 1978 of 9.95 inches. Milwaukee's 12.27 inches made it the wettest June and MONTH on record. The last 90 days have seen over 20 or even 25 inches in parts of the central causing flooding that eclipsed the record 1993 floods in places. There has been some variability with one heat surge during early June perhaps due to weakening La Nina conditions.
 

 
AND SEVERE WEATHER TOO!
 
Severe weather has been very much in the news to the south in the central but has moved into Wisconsin in June. The average number of tornadoes in June in Wisconsin in a given calendar year is 6. So far...we have seen 20 tornadoes in June...far above average. This makes this June the 3rd most active June in terms of numbers of tornadoes in state history.
 
Though there is often good persistence spring to summer of soil moisture (see this Dr. Dew story here), all anomalies eventually end. Will the weakening La Nina make the summer change?
 
Well a soil moisture based regression model by CPC suggests not drastically for July though it does have more normal precipitation for southern Wisconsin. It is still cool over the central. It builds the dry area in the southeast where Charlotte is running a 13 inch deficit the last 12 months. Tropical systems could of course change that.
 

 
This simple model often provides good guidance spring into summer. WSI has several climate and multivariate statistical models it uses and clients of Energy Trader and AgTrader may see a different viewpoint from our seasonal climate expert Todd Crawford. Public releases are provided later. Stay tuned.
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