JACKSONVILLE, Fla. – Tropical Depression Four formed Thursday morning in the open waters of the Atlantic.
It follows Tropical Storm Bret, which formed Monday also in the open Atlantic.
So what do two systems so early mean for the rest of hurricane season? It’s actually unprecedented.
Historical Systems
Tropical Storm Bret alone is a somewhat historical storm.
Systems in the Main Development Region, or MDR, rarely form in the month of June.
But the combination of extremely warm water temperatures and lack of Saharan dust has allowed activity to organize.
Bret is the first June storm -- another Bret developed in 2017.
Bret will impact the Lesser Antilles Thursday night before pushing into the Caribbean.
Tropical Depression Four is expected to become Cindy later Thursday or Friday.
If the depression becomes a storm, it would truly be historic in nature.
No June has ever featured two named storms in the MDR in recorded history.
The Analogs
Meteorologists often use past weather conditions to predict future events.
These past conditions, called analogs, are used to show similarities between other hurricane seasons and how the future may develop.
Only three named storms developed in June in the MDR, which makes the sample size very small.
The three were the Trinidad storm of 1933, Ana 1979 and Bret in 2017. Two of those three seasons were quite busy.
The 1933 season was extremely active, and the 2017 season was above average. The 1979 hurricane season was slightly below average.
There are also other indications that very warm water temperatures in the MDR this early in the season are also an indication of an active season ahead.
A word of caution
One thing that needs to be stressed is the high uncertainty despite the analogs.
We have never seen two named storms in the MDR in June, so this pattern is truly unprecedented. Because it is so historic, it is hard to predict with high accuracy what will happen later this season.
The atmosphere is also transitioning away from a La Nina pattern to an El Nino pattern. This pattern swap will likely help reduce some tropical activity later in the season.
The extremely active start to hurricane season in the open Atlantic is historic in nature. This quick start could forebode an active season ahead, but many factors remain in play.