On Tuesday, a rare event occurred for the earliest time since 1997: four tropical cyclones were simultaneously active in the National Hurricane Center’s area of responsibility (Atlantic and East Pacific). Hurricane Fernanda, Tropical Storm Greg, Tropical Depression Eight-E, and Tropical Storm Don were all simultaneously active Tuesday afternoon, but Tropical Storm Don has likely degenerated into an open tropical wave. The three East Pacific storms should not be a threat to land.

Tropical Storm Don likely now an open wave

An Air Force Reserve Hurricane Hunter aircraft flew into a disorganized Tropical Storm Don Tuesday evening, and was unable to find a well-defined center of circulation. No west winds were found, which indicates that a closed circulation is likely no longer present. NHC will likely confirm that Don has indeed degenerated into a tropical wave at 11:00 p.m. EDT. As of 8:00 p.m. EDT, Don was centered near 11.9°N 61.4°W, and was moving westward at a fast clip of 23 mph. Maximum sustained winds were 35 knots (40 mph), with an estimated minimum pressure of 1011 mb. All that remains with Don is a small area of deep convection located near Grenada. The remnant tropical wave should continue to move quickly westward through the Caribbean Sea, and strong wind shear of over 20 knots should inhibit regeneration. Although Don was weak, it should be noted that having two or more tropical cyclones form in the Atlantic Main Development Region (MDR) before August is not common, and this almost always occurred in a season that ended up above average (except 2013). Don is the third tropical cyclone to form in the region this year, after Tropical Storm Bret in June and Tropical Depression Four earlier this month.

East of Don, Invest 96L has a low chance to develop into a tropical cyclone. NHC gave 96L a 30 percent chance of development within both 48 hours and five days. As of 18:00 UTC Tuesday, 96L was centered near 11.0°N 39.5°W, with maximum sustained winds near 25 knots (30 mph) and an estimated minimum pressure of 1010 mb. Model support for 96L’s development is very limited, and I would be surprised if 96L developed into anything more than a tropical depression at most. Dry air from the Saharan Air Layer (SAL) will likely not allow 96L to develop at all.

East Pacific very busy: three simultaneous tropical cyclones 

The active July in the Eastern Pacific continues. Invest 98E was upgraded to Tropical Depression Eight-E this morning, and Tropical Depression Seven-E strengthened into Tropical Storm Greg. Hurricane Fernanda (left) is now a weakening category 2 hurricane and is not expected to reach Hawaii as a tropical cyclone due to cooling sea surface temperatures. Tropical Depression Eight-E (center) is a sheared cyclone and is not likely to strengthen much, if at all. Tropical Storm Greg (right) is gradually becoming better organized this evening, and could strengthen into a strong tropical storm later this week. The close proximity of Tropical Depression Eight-E and Tropical Storm Greg could cause an interaction between the two storms, and this will be interesting to watch later this week.

In addition to the three cyclones currently active, a new low pressure area is expected to form south of Mexico later this week, and could develop into a tropical cyclone. NHC gives this system a near zero percent chance of development within 48 hours, and a 50 percent chance within five days. The next two East Pacific names are Hilary and Irwin. It is possible that TD Eight-E does not become named, and this new system could develop into Hilary.

I will be back tomorrow for an update on these systems.