DAYSARE WARM­ING UP AHEAD

Sev­eral mod­els sug­gest that El Niño may be com­fort­ably in place as early as May, writes KAREN BRAUN

New Straits Times - - Opinion -

THE path to an­other round of El Niño this year ap­pears to be short­en­ing, as trop­i­cal Pa­cific Ocean wa­ters have been warm­ing at a sub­stan­tial rate.

Weather fore­cast­ers have been eye­ing for a couple of months a pos­si­ble re­turn of the phe­nom­e­non this year, which nor­mally comes around ev­ery two to seven years, and last oc­curred in 2015/16.

The El Niño-South­ern Os­cil­la­tion (Enso) is one of the most widely fol­lowed long-term in­di­ca­tors of cli­mate, as both its warm and cool phases can trig­ger vary­ing ef­fects on weather pat­terns.

El Niño, which is as­so­ci­ated with warmer-than-nor­mal sea sur­face tem­per­a­tures (SSTs) along the equa­to­rial Pa­cific, is known to bring volatile weather to some parts of the world and is closely watched by agri­cul­tural and en­ergy mar­kets.

Some notable im­pacts in­clude droughts in South­east Asia and heavy rains and ero­sion along the Pa­cific coasts of North and South Amer­ica.

La Niña, the cool phase of Enso, just con­cluded its six-month run last month. In the last sev­eral weeks, rem­nants of the colder wa­ters have been all but elim­i­nated.

In the week cen­tred on Feb 22, the SST anom­aly was pos­i­tive 2.3°C in the Niño 1+2 re­gion, the east­ern­most of the four Niño re­gions, di­rectly off the coast of Peru. Warm­ing in this re­gion some­times pre­cedes the on­set of El Niño.

To put this into per­spec­tive, since weekly record-keep­ing be­gan in 1990, the only other in­stances that fea­tured warmer SST anom­alies in this re­gion oc­curred dur­ing the mega El Niños of 2015/16 and 1997/98, as well as the mod­er­ate-to-strong El Niño in early 1992.

The week cen­tred on Jan 25 also recorded a 2°C anom­aly, so the lat­est value is not nec­es­sar­ily an out­lier. But if this trend even­tu­ally trans­lates into a full-on El Niño later in the year, the out­come would be un­prece­dented.

A record-break­ing El Niño sur­faced in mid-2015 and lasted through early last year, af­ter which SSTs dropped off and gave way to the rel­a­tively weaker La Niña event to cap off the year.

But fol­low­ing the pre­vi­ous oc­cur­rences of strong El Niño — 1997/98, 1982/83, 1972/73 — the warm cy­cle did not ap­pear again un­til three or four years later.

So, the pos­si­ble re­turn of El Niño this year will present a unique sit­u­a­tion against which there is not much com­pa­ra­ble data.

Fore­casts in favour

This month, for the first time, El Niño is the most favoured sce­nario over neu­tral or La Niña con­di­tions start­ing in July or Au­gust, ac­cord­ing to the In­ter­na­tional Re­search In­sti­tute and the United States Cli­mate Pre­dic­tion Cen­tre.

The prob­a­bil­ity for El Niño be­tween Au­gust and Oc­to­ber stands at 51 per cent, while the chance of neu­tral is at 38 per cent. But some mod­els are call­ing for El Niño’s ar­rival a bit ear­lier based on the pro­gres­sion of the SSTs in re­cent weeks.

Mon­day’s run of the CFS ver­sion 2 model, main­tained by the US Na­tional Cen­ters for Environmental Pre­dic­tion (NCEP), shows steady El Niño con­di­tions — SST anom­alies of at least 0.5°C — for most of the North­ern Hemi­spheric spring, and then a mod­er­ate to strong event in place by the sum­mer.

The pro­jec­tions of the CFSv2 should be con­sid­ered with cau­tion, how­ever, as the mod­els are run each day with a shift­ing 10day pe­riod of ini­tial model con­di­tions, mean­ing the out­put can be highly de­pen­dent on a small seg­ment of time.

How­ever, other mod­els have been in­creas­ingly lean­ing to­ward both El Niño and its ear­lier on­set.

The lat­est chart of in­ter­na­tional Enso fore­cast mod­els, com­piled by In­ter­na­tional Re­search In­sti­tute for Cli­mate and So­ci­ety and the Cli­mate Pre­dic­tion Cen­tre un­der the NCEP, has shifted in a warmer di­rec­tion com­pared with the pre­vi­ous up­date, and sev­eral mod­els sug­gest that El Niño could be com­fort­ably in place as early as May.

The fore­cast trends are start­ing to show a di­ver­gence be­tween the sta­tis­ti­cal and dy­nam­i­cal mod­els, the lat­ter of which is based on the ac­tual at­mo­spheric and oceanic state rather than his­tor­i­cal ten­den­cies.

Since the dy­nam­i­cal mod­els are now mostly call­ing for El Niño by the start of North­ern Hemi­spheric sum­mer, this gives con­fi­dence that environmental con­di­tions are in­deed turn­ing favourable for the quicker re­turn of the warm cy­cle.

Since the dy­nam­i­cal mod­els are now mostly call­ing for El Niño by the start of North­ern Hemi­spheric sum­mer, this gives con­fi­dence that environmental con­di­tions are in­deed turn­ing favourable for the quicker re­turn of the warm cy­cle.

FILE PIC

A boy cool­ing down in front of a fan dur­ing the hot sea­son of last year’s El Niño cy­cle in March. The pos­si­ble re­turn of El Niño this year will present a unique sit­u­a­tion against which there is not much com­pa­ra­ble data.

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