Bermuda-Azores High July 2013

Mean sea level pressures for the month of July show the location of the Bermuda-Azores high. ESRL reanalysis generated product.
Mean sea level pressures for the month of July show the location of the Bermuda-Azores high. Higher sea level pressures are in warmer colors. The extent of the ridge system is nicely defined by the 1020mb isobar in yellow.  ESRL reanalysis generated product.

For the month of July, the Bermuda-Azores high on average took the two-celled form with a center of high pressure near Bermuda, and another near the Azores connected with a ridge across the Central Atlantic. Both centers of high pressure averaged to be near 1022mb. Looking at anomalies for this month, it reveals that pressures were higher than normal near Bermuda and lower than normal near the Azores, suggesting that the Bermuda-Azores high pressure system was displaced further west than normal.

The higher than climatology pressures near Bermuda associated with the Bermuda-Azores high, and the cell of high pressure to the south of Bermuda during the month of July was very likely related to Bermuda having a very dry July. With 2.36 inches of rain falling in one day and only 0.75 inches for the rest of the month.  High pressure is typically associated with subsidence and limited cloud development and so precipitation is in turn limited. Additionally, July 2013 was near normal in terms of air temperatures as the mean monthly temperature was 81.4°F compared to 1981-2010 climatology of 81.1°F.

In addition, the light winds brought by the cell of high pressure near Bermuda allowed sea surface temperatures to run about 2°F above normal near Bermuda. This could have important implications if this warm pool persists into the peak of hurricane season.

The first half of August had a change in this pattern allowing more active weather into the area, with which significant thunderstorm activity with heavy rain was observed. 5.60 inches of rain have fallen so far this month – according to 1981-2010 climatology, August sees 6.38 inches of rain. We are well on our way to catching up with climatological year-to-date precipitation totals now that the weather has become more changeable. However, now with the Bermuda-Azores high ridging back into our area, Bermuda may have another period without much rain.


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