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Forecasts of the 2018 summer monsoon

The summer monsoon season will soon be starting in South Asia, northern Africa, and north America, so it’s time to check in with forecasts of seasonal rainfall.  India will release its first monsoon forecast in a week or two, and a number of the seasonal forecasts discussed below will be updated in the next week, but it’s nevertheless a good time to take a first look at what might be happening.

IRI/Columbia University is predicting a wet early summer in the Philippines, Southeast Asia, and western Mexico, and a wet late summer in much of Africa (especially East Africa):

The APEC climate center in Korea has many of the same features; because their maps show oceanic rainfall, the wet anomalies over Mexico and the Philippines are more clearly seen as part of a northward shift of the East Pacific ITCZ:

This northward shift of the East Pacific ITCZ isn’t a classic La Niña pattern.  Most of the models are actually forecasting a transition from La Niña to El Niño during summer, but this seems to occur with the cold SST persisting south of the equator in the East Pacific while the northeast Pacific warms, producing that northward shift in the ITCZ that may bring wetness to Mexico, the Philippines (and maybe even SE Asia?).  Here are the SST forecasts from the North American Multi Model Ensemble:

The Australian BoM provides a nice overview of all the large-scale climate modes:  ENSO is nearing neutral, as is the Indian Ocean Dipole.  The BoM model is predicting a negative IOD during June (i.e. cooler SST in the western Indian ocean relative to the east), but there seems to be a fair amount of disagreement in models on this — the NMME forecast shown above looks to be a near neutral for JJA, while even the BoM page shows that only 2 out of 6 models forecast a clear negative IOD phase for June.

Links to the forecasts discussed above:





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