The future of the season 2

[Andrea Griffa]

Hi all,
I'm starting a new thread for 2007 season forecast thoughts.

Last year I tried to imagine how could it be the month of may.
I thought that the 2006 season started up so early and making a comparison, we could compare the month of March and the whole month of April of that year, to a may of a normal year. As to me this was a sign that the season was just well set.
In this way a deductive reasoning did lead me to think that the month of may could be like a normal june and the end of may could be an early july.

We all know how things evolved in the last season.

This year the season is completely influenced by the full activity of the Polar Vortex and USA winter is a demonstration of that. The more spring came near, the more we could understand that the thunderstorms activity was made easier, and you all know that when you have more cold air descent with the polar front that comes down, southern Plains storms(and not only) are more numerous.
So I wanna make a correlation(not necessary scientific) between Nino activity(of the last months) and the strong presence of the polar vortex activity. So we had Nino and USA got a lot of precipitations, strong low pressure systems,snow and tornadic storms(the high number of february's tornado is evident).
At this point there's something to say; first, I don' wanna make any kind of conclusion. I'm monitoring Nino and Nina and from some days and it seems that the Nino pattern is changing into a La Nina pattern..I don't know if it's only a little downfall of the Nino pattern that will last only for a little period, but if you see this map you well understand what's happening:

Anyway I repeat I don't wanna make any conclusion but I'm hoping that things come back in the last months pattern..If the cold air descent tendence still remained the same during this spring, we could have an incredible may.

As conclusion I say that making a similar comparison,(not too much scientific) could be not really representative of the reality, but as last season theaches could be useful in forecasting.

Guys and girls, lemme know your thoughts.

 

[Andrea Griffa]

Here it is another map that can make see that it could be possible that is occurring a changing in the Nino pattern:

 

[Andrea Griffa]

And now I wanna make another thought: watching archive 500mb geopot maps of West pacific I noticed two typical pattern that correspond La nina condition and El Nino condition. I repeat another time I don't want to make any scientific conclusion but it seems that El nino pattern leads to the formation of a strong High pressure with 580-590 values cenetred on Hawaii(in that zone),arranged along meridans, that often sends ridges Norteasthward toward North Western cost promoting a split in the Polar Vortex that allows the descent of strong low pressure systems on the west of United states, that it is ready to traslate toward the Great Plains.

During La nina condition it seems that the strong high pressure on Hawaii is less strong and allows the descent of lows in the west Pacific causing a ridge upon the usa.
That could be the reason why of the long permanence of the death ridges on the last May(La Nina pattern) : the cut off remains isolated in central pacific and allows the formation of the huge and long living ridge upon USA.

This is also the reason why I don't like La Nina pattern for may.

 

[Warren Faidley]

La Niña and Tornado Frequency

An interesting paper from the 19th. Conference of Local Severe Storms in 1999 suggested that La Niña did not have a drastic impact on Plains tornado activity, although data sets from "only 10 El Niños and 8 Niñas over 47 years" could be used for the study.

I would imagine that the intensity of the ENSO events and the transitional timing of the phases (in/out in spring) would also play a part.

http://www.spc.noaa.gov/publications/schaefer/el_nino.htm

Warren

 

[Andrea Griffa]

An interesting paper from the 19th. Conference of Local Severe Storms in 1999 suggested that La Niña did not have a drastic impact on Plains tornado activity, although data sets from "only 10 El Niños and 8 Niñas over 47 years" could be used for the study.

I would imagine that the intensity of the ENSO events and the transitional timing of the phases (in/out in spring) would also play a part.

http://www.spc.noaa.gov/publications/schaefer/el_nino.htm

Warren

Yes Warren,the intensity of La Nino/La nina is another aspect I omitted but is very important..Probably the manifestations of Nino/Nina depend overall on intensity. The more La Nino/El Nino are intense, the more we see their effects on climate.

 

[Andrea Griffa]

Finally I'm starting to see a changing in this last pattern that did lead the weather in these last days.
GFS is showing a new short wave that could give a start to the season.
Now it remains to see if things will be confirmed.