Chances of weak El Niño are good, fore­cast­ers say

Fore­cast­ing models sug­gest it’s likely later, but cli­mate pat­tern has yet to shift.

Los Angeles Times - - CALIFORNIA - JU­LIA ROSEN

Con­di­tions have been brew­ing in the trop­i­cal Pa­cific, but the cli­mate pat­tern still hasn’t clicked into place.

For months, El Niño con­di­tions have been brew­ing in the trop­i­cal Pa­cific. But the cli­mate pat­tern still hasn’t clicked into place, fore­cast­ers said Thurs­day.

Sur­face wa­ters in the east­ern part of the Pa­cific basin have warmed, as they would dur­ing a full-blown El Niño. But cir­cu­la­tion pat­terns in the at­mos­phere have not shifted as ex­pected, ac­cord­ing to a monthly up­date is­sued by the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion’s Cli­mate Pre­dic­tion Cen­ter and the In­ter­na­tional Re­search In­sti­tute for Cli­mate and So­ci­ety at Columbia Univer­sity.

That means Cal­i­for­ni­ans will have to keep wait­ing to see what kind of weather the win­ter brings.

El Niño can in­crease the odds of a wet­ter year in South­ern Cal­i­for­nia, said Nina Oak­ley, re­gional cli­ma­tol­o­gist at the Western Re­gional Cli­mate Cen­ter. How­ever, it’s not guar­an­teed, and “the re­la­tion­ship is a lit­tle more ten­u­ous as you get into the north­ern two-thirds of the state.”

Part of the rea­son an El Niño hasn’t formed yet is that an­other cli­mate phe­nom­e­non — known as the Mad­den-Ju­lian Os­cil­la­tion — is cur­rently in an op­pos­ing phase, said Tony Barn­ston, chief fore­caster at IRI.

The MJO can be thought of as a clus­ter of thun­der­storms that mi­grates across the trop­ics. Right now, it’s cen­tered over the western part of the Pa­cific, near In­done­sia, where it coun­ter­acts the at­mo­spheric cir­cu­la­tion pat­tern that nor­mally es­tab­lishes dur­ing El Niño.

But as the MJO moves east­ward over the com­ing month, it should pro­mote El Niño for­ma­tion, Barn­ston said.

Fore­cast­ing models sug­gest it’s still likely that El Niño will take shape later this win­ter. Thurs­day’s re­port puts the odds at 65% — down from 90% in De­cem­ber.

By the time El Niño does ar­rive, it prob­a­bly won’t bring huge changes to weather pat­terns, the fore­cast­ers wrote in the re­port: “Given the tim­ing and that a weak event is fa­vored, sig­nif­i­cant global im­pacts are not an­tic­i­pated dur­ing the re­main­der of win­ter, even if con­di­tions were to form.”

For South­ern Cal­i­for­nia, that means the chances of in­creased rain­fall are not as good as they would be dur­ing a stronger and longer­lived El Niño, Barn­ston said. But the re­gion could still see higher-than-nor­mal pre­cip­i­ta­tion later in the win­ter and spring.

NOAA’s sea­sonal out­look for the next three months, also re­leased Thurs­day, sug­gests greater odds of above-av­er­age rain­fall in the state’s south­east­ern deserts, below-av­er­age pre­cip­i­ta­tion in the north­west cor­ner of the state and an equal chance of ei­ther — or nei­ther — for the ar­eas in be­tween.

In re­al­ity, it’s been a dry sea­son for much of Cal­i­for­nia so far.

“There have been sev­eral re­cent storms, which is great,” Oak­ley said. “But de­spite the re­cent pre­cip­i­ta­tion, much of Cal­i­for­nia is still re­port­ing below-nor­mal wa­ter years since Oct. 1.”

That’s im­por­tant in­for­ma­tion for manag­ing wa­ter sup­plies. But Oak­ley stresses that the to­tal pre­cip­i­ta­tion out­look does not di­rectly af­fect the like­li­hood of haz­ards such as post­wild­fire land­slides, which can be trig­gered by a sin­gle pulse of pre­cip­i­ta­tion.

“All it takes is that one storm with high-in­ten­sity rain­fall in it,” she said.

Thurs­day’s fore­cast came out de­spite the par­tial gov­ern­ment shut­down and was not sig­nif­i­cantly af­fected by it, Barn­ston said. Most fore­cast­ers are con­sid­ered es­sen­tial staff, he said, and the models they rely on run au­to­mat­i­cally.

Fore­cast­ers, how­ever, did make ad­just­ments be­cause some of the data they nor­mally used were not avail­able for De­cem­ber.

A net­work of NOAA­op­er­ated buoys in the trop­i­cal Pa­cific that mea­sure ocean and air tem­per­a­tures and wind speed did not up­date, Barn­ston said. It’s un­clear why; the sci­en­tist in charge of the project was fur­loughed and could not be reached.

Re­searchers also had to make do with­out an­other data set of sea sur­face tem­per­a­tures. Luck­ily, they had ac­cess to dif­fer­ent mea­sure­ments, which they could use in­stead.

“It’s like a me­chanic who’s miss­ing a few tools in the tool chest,” Barn­ston said. “There are other tools that can do the same thing. It might have taken five to 10 min­utes longer, which is not a big deal.”

The most no­table ef­fect of the shut­down was on the Cli­mate Pre­dic­tion Cen­ter’s ac­tiv­i­ties. Gov­ern­ment fore­cast­ers can’t speak with the pub­lic or elab­o­rate on the new re­port on­line be­cause the Cli­ web­site is unavail­able.

Linda Strat­ton NOAA

FORE­CAST­ERS had to make ad­just­ments be­cause some data for De­cem­ber were not avail­able. Mea­sure­ments from a net­work of buoys in the trop­i­cal Pa­cific did not up­date and the sci­en­tist who over­sees the project was fur­loughed be­cause of the par­tial gov­ern­ment shut­down.

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