Bermuda-Azores high firmly in place


Pink arrows show general surface flow around Bermuda-Azores high today. Ridge marked with jagged black line connecting blue 'H's and trough marked with dashed black line. Convergence indicated by red arrow and red hatched area. That area should be headed eastwards - towards Bermuda.
 – GOES imagery from this morning with my annotations. Pink arrows show general surface flow around Bermuda-Azores high today. Ridge marked with jagged black line connecting blue ‘H’s and trough marked with dashed black line. Wind around trough responsible for convergence indicated by the red arrow, while the convergence itself is marked by the red hatched area. 

With the highest pressures centered over the Azores, the Bermuda-Azores high extends ridging westward into the Western Atlantic, controlling the weather in the area around Bermuda. However, as is fairly common, a secondary center of high pressure is trying to form nearer Bermuda and between these to centers weak troughing can exist. Essentially between two areas of relatively high pressure, there is an area of relatively low pressure, the flow around which allows for surface convergence and shower activity. This is the set up today. Weak troughing trapped between these two centers of high pressure is enhancing convergence to the east of Bermuda. This trough has detached from the mid-latitude westerly flow and should quickly get caught in the easterly trade winds and head westwards towards Bermuda bringing an increased chance for showery precipitation beginning late tonight and continuing through tomorrow, at least through the morning.

Expect isolated showers, winds generally easterly with some backing ahead of the trough and veering behind the trough. Winds should remain moderate through the day tomorrow.

Despite the trough passing tomorrow, the Bermuda-Azores high is still the dominating weather feature. In fact, for much of the official forecast period, the trough is the only organized chance for precipitation. Even into the extended period – some forecast models provide guidance to two weeks with a grain of salt – Bermuda should remain fairly dry. That being said, things can change pretty quickly. Not to mention isolated shower activity due to convergence and island convective activity such the Morgan’s Cloud phenomena can never be ruled out in moist tropical airmasses like the one we will likely be stuck in for the majority of the period – as is typical in Summer.

An extended dry spell seems imminent based on the latest forecast model guidance and climatologically favored scenarios based on the positioning of the Bermuda-Azores high. But on the flip side, that means relatively good weather for outdoor activities, albeit warm and muggy at times.

Of course, stay tuned to the latest official forecasts by the Bermuda Weather Service – including the latest on Tropical Cyclone activity in the Atlantic. Tropical Cyclone forecasts can also be found at Miami’s National Hurricane Center.

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