North Atlantic ITCZ is Stronger; Tropical Disturbance Forming

Highlight: ITCZ is stronger. Tropical disturbance may form.

Fig. 1: Morning satellite view of the North Atlantic basin.

Discussion: Seasonality is increasing influence on the deep tropics. Over-the-weekend, the intra-tropical convergence zone (ITCZ) strengthened primarily due to a light shear pattern and water-than-normal SSTA in the central/east North Atlantic tropics. Embedded within the ITCZ is an area of low pressure. Unclear is how much development will occur with this system. Forecast models indicate a 5-day track toward or just northeast of the northeast Caribbean Sea. At that location an upper shear axis likely weakens this system. However, prior to arrival there is risk of a tropical system developing and therefore an ALERT for the central tropics is issued. The cold front that ends the Northeast Corridor heatwave midweek stalls offshore and may catch shortwave energy aloft that produces a low-pressure system rapidly gaining subtropical characteristics. If so, a subtropical storm might develop and move into Nova Scotia next weekend. The tropical upper tropospheric trough (TUTT) is producing scattered thunderstorms in the Gulf of Mexico eastward to the northern Caribbean Sea.