No pre­dic­tion yet

The Queens County Advance - - NEWS -

Re­quests for a pre­dic­tion for the up­com­ing win­ter are start­ing al­ready, but the de­vel­op­ments through the re­main­der of Oc­to­ber and Novem­ber are sig­nif­i­cant to the chances of get­ting it right.

Com­ments on my pre­dic­tions and weather/cli­mate com­men­taries fall into two cat­e­gories: Those from peo­ple who have rec­og­nized that the ma­jor­ity of my pre­dic­tions for both tem­per­a­ture and snow­fall have been cor­rect dur­ing the past 12 win­ters, and from those who good na­turedly chide me about how ac­cu­rate I am about weather that has al­ready occurred.

With this in mind, I thought I’d give a bit of a sum­mary of some of the re­search and past con­di­tions that help to im­prove the chances for pre­dic­tions to be cor­rect.

By way of ex­pla­na­tion, me­te­o­rol­o­gists need the very best and lat­est of data and im­ages for a cor­rect short­term fore­cast. For long-term fore­casts, cur­rent con­di­tions, or those dur­ing the past month, or even the past year do not shed suf­fi­cient light on what may hap­pen over the next four months. I use sea­sonal, 12 month, and five-year trends along with long-term cli­mate change to sup­ple­ment other in­for­ma­tion that is oc­cur­ring glob­ally.

Read­ers might be in­ter­ested in a re­cent study that I con­ducted to try to de­ter­mine the on­set and ef­fect of cli­mate change in this part of the world. My data for tem­per­a­ture, snow­fall and to­tal pre­cip­i­ta­tion goes back to 1966. I used the 25-year pe­riod from 1966 to 1990 as a ref­er­ence pe­riod and com­pared that to the data since that time, which cov­ers 18 years to the end of 2008. It hap­pened that the year 1990 was the warmest year to that point, sig­ni­fy­ing that the im­pact of cli­mate change may have started for coastal Nova Sco­tia. It was sig­nif­i­cant that no ap­par­ent warm­ing trend had occurred in this area over the pre­vi­ous 50 years. The warmest year on record for this area was es­tab­lished occurred since 1991. There have been sev­eral flood or near flood oc­cur­rences dur­ing this pe­riod, a rate much higher than dur­ing the pre­vi­ous 25 years. Sur­pris­ingly av­er­age snow­fall has been es­sen­tially un­changed.

The tem­per­a­ture tells a dif­fer­ent story. The av­er­age tem­per­a­ture has been a half de­gree higher since 1991 than the pre­vi­ous 25 years. That doesn’t seem like much but when one con­sid­ers that global warm­ing is rep­re­sented by about one de­gree over the past 100 years, a half de­gree in less than 20 years is very sig­nif­i­cant.

What does all this have to do with win­ter? Both win­ter and late sum­mer/ fall have av­er­aged warmer since 1991 than the 25-year ref­er­ence. Only the May to July pe­riod has been rel­a­tively the same. The fact that win­ters have av­er­aged warmer is a bit mis­lead­ing. Nor­mal win­ters have been rare, an­other il­lus­tra­tion of a ten­dency to ex­tremes that has been an­tic­i­pated with global warm­ing. Dur­ing 19 win­ters from 1991 to 2009, six were rel­a­tively se­vere, 10 were very mild and only two were nor­mal. The win­ter of 2008 was very un­usual in that it was rel­a­tively mild but with a lot of snow. This cer­tainly il­lus­trates that pre­dict­ing a nor­mal win­ter is not the safe way out.

How does this fac­tor into a pre­dic­tion for this win­ter? That will be the sub­ject of the next ar­ti­cle, which will in­clude ob­ser­va­tions of trends and the in­di­ca­tors from sum­mer and fall con­di­tions. Don’t ex­pect a pre­dic­tion un­til the end of Novem­ber.

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