Fig. 1-2: High-level TUTT presence during August 2022 and the last time TUTT was strong during August in 2013.
Discussion: Presence of an upper-level low-pressure trough in the upper troposphere developed late last spring and lingered through meteorological summer. The upper trough is weaker in late August but still evident stretching from the Bahamas southwestward (Fig. 1). The last time a tropical upper tropospheric trough was present during August in a vivid character was 2013 (Fig. 2). The 2013 version was much stronger but occurred during a weak La Nina climate. Prior to the 2013 tropical cyclone season, forecasters predicted 8 hurricanes and 4 intense hurricanes. Only 2 hurricanes formed and no major hurricanes due to presence of TUTT. The TUTT pattern is the one way to knock down the sure-fire correlation between La Nina and active hurricane seasons. Currently, seasonal forecasts indicate 6-10 hurricanes and 3-5 major hurricanes in 2022. Clearly, these numbers are likely too high. However, as indicated earlier, Climate Impact Company does expect a significant uptick in hurricane risk in the Gulf of Mexico later this month.
Fig. 3: The 100-250 MB wind direction and speed across and just north of the Caribbean Sea are identified and formulate a weak TUTT pattern.
Fig. 4: The TUTT pattern is responsible for mid-level tropospheric shear inhibiting tropical cyclone development.