MJO More Favorable for Tropics Later August

ECMWF forecasts favorable MJO for North Atlantic tropical cyclones later this month.

Operational models showing Gulf of Mexico risk.

Fig. 1: Today’s ECMWF 15-day forecast of the Madden Julian oscillation shifting from the Maritime Continent (now) to Western Hemisphere and Africa in 2 weeks.

Discussion: Emergence of phase_1/phase_2 of the Madden Julian oscillation implies increased vertical motion and lowering upper level wind shear in the tropical North Atlantic (where tropical cyclones develop) and tropical Africa (where tropical waves which become Atlantic tropical cyclones develop). The MJO has anchored over Maritime Continent/West Pacific tropics recently certainly contributing to an increase in tropical cyclone activity. However, today’s ECMWF MJO forecast indicates MJO weakens over Maritime Continent and is likely to regenerate over the tropical North Atlantic/Africa in 2 weeks (Fig. 1).

The implication is an improving environment for tropical cyclone development in the North Atlantic basin the last 7-10 days of August. The ECMWF develops a hybrid system in the northeast/north Gulf of Mexico Aug. 20-21 which forms close enough to land to prevent a full-blown tropical system (Fig. 2). Meanwhile the GFS indicates a tropical system moving into the Gulf of Mexico from the Caribbean Sea bringing heavy rain to a similar location Aug. 24-25 (Fig. 3).

A busy tropical cyclone season is ahead and may initiate the last third of August. A close eye on the MJO forecasts and operational models for 10+ day forecasts is increasingly important.

Fig. 2-3: Forecast models are starting to show tropical threats in the extended-range forecasts…ECMWF in northern Gulf Aug. 20-21 and GFS in a similar location Aug. 24-25.