This morning, Tropical Storm Calvin in the East Pacific and Tropical Storm Merbok in the West Pacific both dissipated inland Mexico and China, respectively. So far, no fatalities or significant damage have been reported from either storm. The Pacific should remain quiet for a while, and the Atlantic basin is now the basin to watch.

The National Hurricane Center (NHC) first noted the possibility of development in the Western Caribbean in five days this morning in its 8:00 AM EDT Tropical Weather Outlook (TWO), with a near zero percent chance of development in 48 hours and a 20 percent chance of development within five days.  In its 2:00 PM EDT TWO, NHC kept its development probabilities the same for both 48 hours and five days. Models continue to be consistent with the formation of a broad area of low pressure from a monsoon gyre in the Northwestern Caribbean in four to five days, with the system crossing over the Yucatan and emerging into the Bay of Campeche.  A strong ridge of high pressure over the Southeastern United States will likely keep the system confined to the Bay of Campeche, and a United States landfall (except for maybe South Texas) is looking very unlikely as of this time. However, uncertainty remains considering the system is not expected to enter the Bay of Campeche for another week.

The 12z Tuesday GFS, ECMWF, and CMC all predicted a large tropical low to develop within five days, eventually emerging to the Bay of Campeche by early next week.  June Bay of Campeche tropical storms are somewhat common – several have formed this decade (such as Tropical Storm Arlene in 2011, Tropical Storm Barry in 2013 and Tropical Storm Danielle in 2016). However, this system will be somewhat larger than most Bay of Campeche systems, and its large size may hinder development. Due to land interaction and the broad nature of the system, a hurricane is very unlikely from this system. The most likely scenario is either a broad tropical low or a disorganized tropical storm over the Bay of Campeche. Models are not optimistic with development occurring before it crosses the Yucatan, but this does remain a distinct possibility.  If development does occur, I expect it to be in the Bay of Campeche. I continue to give this system a 40 percent chance of developing into Tropical Storm Bret over the next ten days.

In addition, a vigorous tropical wave, accompanied by moderate to strong convective activity and winds of near 30 knots (35 mph) exited the African coast last night. This tropical wave is unusually strong for the month of June. In fact, the 12z Tuesday GFS model run and earlier ECMWF model runs have suggested the possibility of it developing into a small, weak tropical cyclone southeast of the Lesser Antilles. This is an unlikely scenario at best, and it is not favored by climatology. I give this system a 10 percent chance of developing into a tropical depression over the next week.

Based on the two systems, I give a 50 percent chance of Tropical Storm Bret forming during the next ten days, up from 40 percent yesterday, taking into account the new tropical wave. I will be back for another blog post tomorrow discussing these two Atlantic systems.