Strengthening La Nina and -IOD Pattern

Fluctuating Weak-to-Moderate Strength La Nina
09/12/2022, 12:10 pm EDT
Central/Northern Oceans Are Very Warm and Sustain North-traveling Tropical Cyclones in SEP/OCT
09/15/2022, 12:23 pm EDT
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Discussion: Important changes are emerging in the tropical SSTA patterns. In the eastern equatorial Pacific Ocean dramatic cooling has generated the past 1-2 weeks. La Nina is gaining strength rapidly! The Nino3 SSTA region located in the east-central Pacific Ocean equatorial region has cooled to -1.12C which represents moderate-to-strong La Nina (Fig. 1). More impressive is the cooling of the past 2 weeks to -1.70C in the Nino12 region just-off the northwest coast of South America (Fig. 2). The cooling zones will expand westward the second half of September as La Nina intensifies. In the tropical Indian Ocean, the eastern basin has turned moderately cooler than normal (Fig. 3) while the eastern basin has warmed dramatically (Fig. 4). The differential leads to a strong negative phase of the Indian Ocean Dipole likely to strengthen early in Q4 of 2022. Effects of strengthening La Nina include a drier regime for the U.S. Gulf States, wetter Eastern Australia, drier northeast Argentina/southeast Brazil and wetter Indonesia.

Fig. 1-2: The Nino12 SSTA region off the northwest coast of South America has cooled dramatically. Also cooling moderately is the east-central equatorial Pacific Nino3 region.

Fig. 3-4: The Indian Ocean Dipole has strengthened dramatically and is now considered quite strong given the differential between the cool West Indian Ocean tropics and much warmer eastern areas.