A fast start to the hurricane season with 5 named storms has now gone dormant East and South of the USA.

Tropical Storm Elsa was back in early July but after that we have been in a quiet spell in the Atlantic and Caribbean.

A combination of a dry dusty layer of air (SAL) from North Africa making the air drier and more stable over the ocean, unfavorably high wind shear over the ocean preventing organization of thunderstorms, a lack of good low pressure waves in the flow, and a negative downward sinking large-scale air flow pattern (subsidence from MJO phase) have all put a lid on tropical development.

This is expected to continue for at least a couple weeks longer. But IF global models are correct in their projections for the future state of the MJO then the pattern over the Atlantic and adjacent areas may become more favorable for development (or at least less hostile to development).

The models are not so great at MJO projections in general, and of course especially so going out a month or more.

In addition the MJO forecast phase is not strong so this does not guarantee a tropical storm will form sometime next month.

But sometimes the models do well in giving us a signal and right now most of them agree in a more positive phase for development starting between August 10 and 15th perhaps lasting beyond that.

However it’s worth noting that the signal in the forecast phase diagrams is on the weaker side (near the null circle as you’ll see).

Depending on the model the shift begins at the end of this month or (later on other models) before becoming more unfavorable again in September for at least a while. The Pacific goes in the opposite directions:

The dynamic and statistical models forecast for MJO Phase (the signal is strong if away from the center circle, weak if near or in circle):

Forecast phases 5-6 (maybe 7):

MJO PHASES 1-8:

The phases 1, 2, 7 and 8 are the ones with more favorable outflow aloft (upper level divergence) in the Gulf and/or Atlantic which means tropical thunderstorm clusters have a better chance to organize and develop as surface pressure drops.

Favored tracks in the “warm colors” by MJO Phase IF the signal is strong enough:

The MJO is also used in long-range forecasting of temperature and precipitation in all seasons (one of many tools). This is for the average of July-September:

VARIOUS MJO FORECASTS FROM DIFFERENT MODEL SYSTEMS:

Analog years from the past that are close to current observations of sea-surface temperature patterns in the Pacific/Atlantic and African Sahel since 1870 hint at lower than normal surface pressure in green for the heart of the hurricane season suggestive of a possible favored zone:

Analogs from past years with big heat in the West/NW:

Rainfall anomaly from those past analog years for August-October:

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