DISCUSSION: Tropical cyclones derive their energy from evaporation from the sea surface, and warmer water allows for greater evaporation. In addition, liquid water has an enormous heat capacity, meaning it takes a lot of energy/a long time to change its temperature. Thus, sea surface temperatures (SSTs) and related phenomena (e.g., the El Nino Southern Oscillation [ENSO]) can be used in longer term forecasting of tropical cyclone activity or other types of weather.
The figure above shows the SST anomalies in the western hemisphere valid on 7 June 2018 from the NOAA Office of Satellite and Product Operations website. The blues show cooler-than-normal water, while yellows/oranges indicate above-normal temperatures. The NOAA Climate Prediction Center (CPC) indicates that conditions in the tropical Pacific are currently ENSO-neutral. If you were to draw a box across the equator in the east Pacific shown above, the combination of slightly below-normal SSTs south of the equator and slightly above-normal SSTs north of the equator, would probably combine to give near normal SSTs there, consistent with the CPC. Looking at the tropical Atlantic in an area stretching from the coast of Africa to ~60W and from ~5-20N (where the strongest tropical cyclones in the Atlantic basin tend to develop), predominantly below-normal SSTs exist. El Nino (La Nina) tends to inhibit (intensify) tropical cyclone activity in the Atlantic basin, while ENSO-neutral conditions don't provide a strong forcing for or against Atlantic tropical cyclone activity. However, the cool SSTs in the tropical Atlantic are not favorable for storm formation. Based on the discussion above, we may expect these cool Atlantic SSTs and ENSO-neutral conditions to persist for at least the next month or two.
The CPC has predicted a normal to slightly above-normal tropical cyclone season in the Atlantic this season (for more information on this forecast click here). An important question to ask is whether the information above, specifically the cool Atlantic SSTs, is inconsistent with the CPC's outlook. The answer to that question is not necessarily. Many of the strongest storms tend to form in the area indicated above off the coast of Africa, but destructive storms can also develop in the Gulf of Mexico and off the eastern seaboard of the U. S. where water is currently warmer than normal. In addition, three months from now in the climatological peak of the Atlantic hurricane season, the waters may warm up in the main development region. Hence, despite the cooler waters in the tropical Atlantic today, if you live in a hurricane-prone region around the Atlantic basin, it is still important now to prepare for whatever this season brings.
To learn more about other tropical cyclone related stories from around the world, be sure to click here!
© 2018 Meteorologist Dr. Ken Leppert II
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