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Tropical Weather Update - 10/16/2021


The Atlantic basin is rather quiet as we move into mid-October and into the last third of the 2021 Atlantic hurricane season. Taking a look back at what the 2021 Atlantic hurricane season has entailed, 20 named storms so far, well above the 14 average. Seven hurricanes, four of which were considered major (CAT 3+), 159 fatalities, and an estimated $69.513 billion in damage, making it the four costliest season on record.


The Atlantic will remain quiet over the next couple of days with no areas of interest in the Atlantic, as noted by the National Hurricane Center (NHC). Dry air and Saharan dust are moving across the eastern Tropical Atlantic off the west coast of Africa, inhibiting tropical development in that region. Across the central and northern Atlantic, unfavorable wind shear continues to disrupt tropical development.


We have been in an unfavorable phase of the Madden Julian Oscillation (MJO) over the Tropical Atlantic and Africa, limiting thunderstorms due to suppressed air and increased wind shear producing a multi-week period of lack of tropical storms. However, as we look at the two graphics below, over the next one to two weeks, we see us go to a more neutral to an enhanced phase of the MJO. The MJO not only increases rainfall during its enhanced phase but also decreases wind shear. The enhanced phase also creates an environment favorable for new tropical waves to develop and organize.

Long Range GFS shows a couple of possible disturbances developing in both the Atlantic and the Gulf over the next couple of weeks. The first disturbance is a weak area of low pressure and a cluster of thunderstorms forecasted to develop across the southern Atlantic between the 19th and the 21st. I have low confidence in tropical development across this region. The second area of interest is a cluster of thunderstorms forecasted to form off the western coast of Mexico near Guatemala and is forecasted to move across Mexico and develop into an area of low pressure in the Gulf of Mexico. I give this low confidence due to this being over 250hours out on the GFS and much can change over the next couple of days. However, weak wind shear and very warm ocean waters near 30C or 86°F are currently over the Gulf. These favorable conditions I expect to continue, so if this cluster of thunderstorms does develop I suspect it to develop rapidly into a tropical storm. The last area at the end of the 6z GFS run near the 30th of October is the possibility for the development of a tropical easterly wave off the coast of Africa, again low confidence as this is on the tail end of the current GFS run and could possibly drop off on the next run as the models tend to exaggerate and deviate a lot due to the simplification of equations in weather models to make them run faster, the lower resolution of the GFS to other models, and for computing power, tend to make these models not be reliable past 120 hours. We will continue to monitor to see if the GFS and other models pick up on these tropical disturbances over the next couple of days. Again this is not a forecast but a model suggestion.


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