[Sea surface temperature (SST) Anomalies before Arthur]
[Sea surface temperature (SST) Anomalies after Arthur]
In their very essence, tropical storms are “heat machines” that are fueled by warm sea surface temperatures and they are one of mother nature’s most efficient methods of transporting heat from the tropics to the mid and high latitudes in her ceaseless attempt at balancing out the atmosphere. Often, there can be an immediate impact in this perpetual balancing act of nature with respect to sea surface temperatures in areas near the path of a tropical storm. In fact, Hurricane Arthur, which moved on Friday from the Outer Banks of North Carolina to off the Mid-Atlantic coastline, generated a dramatic drop in sea surface temperatures at the Jersey Shore. As the tropical storm moved over nearby ocean waters, it acted to churn up the water at the Jersey Shore so that colder water from lower levels in the ocean rose to the surface in a process caused “upwelling”. In the same manner that warm air rises and cold air sinks in the atmosphere, cold water will typically sink to lower levels in the ocean as it is more dense than warm water. The “upwelling” generated by Arthur helped to cause sea surface temperatures to plunge at the Jersey Shore from the lower 70’s on Thursday to the upper 50’s on Friday – they have since recovered some back to the lower 60’s. In fact, sea surface temperatures dropped significantly from “pre-to-post Arthur” off the southeast US coastline where Arthur first formed and hovered for a few days (see “before and after” SST maps above). While the change in sea surface temperatures is usually just a short-term phenomenon on the order of days and not weeks, it can act to suppress any new tropical activity until sea surface temperatures climb back to warmer-than-normal levels.