European Model: 3 Tropical Events North Atlantic Next Wednesday

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The North Atlantic basin is about to turn tropically active. The ECMWF indicates potential for 3 tropical systems middle of next week.

Discussion: ALL CLEAR across the North Atlantic basin this morning. However, changes are on the way. NOAA/NHC identifies a tropical wave yet to move off the coast of West Africa having a 50% chance of becoming a tropical storm in the Cape Verde Islands after 48 hours. The ECMWF model indicates the new tropical storm in the Cape Verde Islands late this week moves to the central subtropical North Atlantic basin by early Wednesday next week. At that time the ECMWF takes a tropical wave that develops in the Bahamas this weekend into the north/northeast Gulf of Mexico possibly becoming a tropical storm. Mid-next week may also produce a 3rd event, a tropical depression in the outer tropical North Atlantic.

The upper shear preventing activity from forming so far this summer remains hostile with 2 axis of upper shear across the southern Caribbean and northern Caribbean Islands (Fig. 1). This upper shear pattern will need to weaken substantially for the ECMWF forecast to verify.  The convection phase of the Madden Julian oscillation is expected to shift to the western hemisphere tropics in early September which should ease the shear pattern.

The outer North Atlantic tropics has warmed to near to slightly above normal in recent weeks after a lengthy period of cooler than normal conditions early-to-middle summer. The Gulf of Mexico is somewhat warmer than normal (Fig. 2).

Fig. 1: The upper shear axis analysis across the North Atlantic basin.

Fig. 2: The Gulf of Mexico sea surface temperature anomalies.