June 1st represents the start of meteorological summer and the Atlantic hurricane season. Interestingly, the past five seasons have included a named system before that date. In May, Subtropical storm Andrea formed in the Atlantic Ocean between the Bahamas and Bermuda. As I write this article, the National Hurricane Season is monitoring a system in the western Caribbean and gives it a 60 percent chance of further development (Note: Keep reading for the latest update). According to WeatherBug.com, fully developed hurricanes are relatively rare in June. In fact, the website states that "Statistically, half of all the Junes since modern weather records began do not see any named storms form (see the graphic at the end of the essay for more context)." If something does form, where is it likely to be and why?
The answer to that question is Gulf of Mexico, western Caribbean, or western Atlantic Ocean close to the U.S. East Coast. Not surprisingly, these areas are exactly where we saw Andrea form in May and is where Invest 91L (graphic above) has developed. An Invest, according to the National Oceanic and Atmospheric Administration, is:
A weather system for which a tropical cyclone forecast center (NHC, CPHC, or JTWC) is interested in collecting specialized data sets (e.g., microwave imagery) and/or running model guidance....The designation of a system as an invest does not correspond to any particular likelihood of development of the system into a tropical cyclone
According to the 8:00 am Monday CST Tropical Weather Outlook from the National Hurricane Center:
A broad area of low pressure is producing disorganized shower and
will likely produce heavy rainfall over portions of southern and
thunderstorm activity over the Bay of Campeche. This system is
expected to move slowly northwestward toward the northeastern coast
of Mexico, and could become a tropical cyclone before it moves
inland in a day or two. Regardless of development, the disturbance
eastern Mexico during the next few days. An Air Force Reserve
reconnaissance aircraft will investigate the disturbance this
afternoon, if necessary. Interests along the Gulf coast of Mexico
should monitor the progress of this system.
This system is climatologically right where it is supposed to be. If you look at the tropical cyclone origins points from 1851 to 2015 (above), they are typically found in the Gulf of Mexico or western Caribbean Sea. There is also a formation cluster in the eastern Pacific Ocean just to the west of Central America. The eastern Pacific hurricane season starts May 15th. FEMA planning specialist and former Weather Channel hurricane expert Michael Lowry issued the Tweet and graphic below on June 1st about the system near the Bay of Campeche.
What is it about this region and the early part of the Atlantic hurricane season? I reached out to hurricane expert Brian Mcnoldy. Mcnoldy is a researcher at the University of Miami and a contributor to the Washington Post Capital Weather Gang. He told me:
This time of year, the majority of the Atlantic is still not very accommodating to fledgling storms. Either the water is too cool, there's too much wind shear, and/or too much dry Saharan air. The Gulf and western Caribbean are typically the first places to get the green light.
By the way, the question is often raised about whether an active early hurricane season is a harbinger for more activity in the peak of the season (August to October). A NOAA Hurricane Research Division FAQ website suggests that the answer is "yes and no." A Hurricane Research Division website points out that "The overall number of named storms (hurricanes) occurring in June and July (JJ) correlates at an insignificant r = +0.13 (+0.02) versus the whole season activity." There is even a negative correlation between the early season and late season. However, the same website points out that a 2000 study suggested that activity in the eastern part of the Atlantic Main Development Region does have a stronger association with the remaining season.
