The Northern Hemisphere tropics remain active today, with Tropical Storm Calvin being named in the East Pacific, Tropical Storm Merbok making landfall in Hong Kong, and the development threat in the Caribbean or Gulf of Mexico by early next week.

TROPICAL STORM CALVIN IS BORN

The organization of Tropical Depression Three-E improved enough on Monday afternoon for the National Hurricane Center to upgrade it to Tropical Storm Calvin at 5:00 PM EDT (4:00 PM CDT local time). Calvin is the third named storm of the 2017 Pacific hurricane season – which is above average – however it almost certainly will continue the season’s start with many weak storms.

At 4:00 PM CDT, Calvin was centered near 15.5°N 95.5°W. Maximum sustained winds were estimated to be 35 knots (40 mph), with a minimum pressure of 1005 mb. The cyclone was named based on Dvorak T-numbers a consensus T2.5 from both the TAFB and SAB, in addition to Automated ADT values of T3.1.  The NHC expects Calvin to make landfall in about six hours or so in the Mexican State of Oaxaca, very near where Tropical Storm Beatriz made landfall earlier this month. Some slight strengthening cannot be ruled out prior to landfall, but the cyclone is likely to close to land for any rapid intensification to occur.  Calvin will then likely dissipate over the mountainous terrain of Mexico tomorrow. The primary threat with Calvin, much like Tropical Storm Beatriz, is heavy rains; however, Calvin is somewhat smaller with Beatriz was, and this will hopefully result in Calvin bringing less flooding than Beatriz.

TROPICAL STORM MERBOK MAKES LANDFALL 

Tropical Storm Merbok has weakened this afternoon after peaking in intensity this morning just before landfall in Hong Kong. Merbok, the second named storm of the 2017 Pacific typhoon season, peaked with maximum sustained winds of about 50 knots (60 mph), a Severe Tropical Storm on the JMA scale.  As of 18:00 UTC this afternoon, Merbok has weakened, and maximum 1-minute sustained winds are now estimated to be 40 knots (45 mph). Merbok should move northeastward, inland into China, before dissipating by late tomorrow.

MODELS STILL INDICATING POSSIBILITY OF CARIBBEAN/GULF OF MEXICO DEVELOPMENT 

Tropical development in the Northwestern Caribbean or Gulf of Mexico continues to remain a distinct possibility, as suggested by numerous computer models. The 12z Monday GFS and CMC models continued to predict development of at least a tropical depression by next Monday. Models today have become more uniform in predicting a track in the Southern Gulf of Mexico, perhaps as far south as the Bay of Campeche. In fact…the 12z Monday ECMWF run shows the system being too far south to even develop into a tropical cyclone. I continue to give this system a 40 percent chance of becoming Tropical Storm Bret over the next ten days, but land interaction and the large size of the system will likely hinder significant development. The National Hurricane Center has not mentioned this system on its tropical weather outlook.

Alternatively…a few 12z GEFS ensembles as well as the 12z ECMWF indicated the slight chance of a tropical cyclone forming in the deep tropics east of the Lesser Antilles by next week, from a vigorous tropical wave. However, development in this region is not favored by climatology, so it is unlikely this system will amount to anything. I give this deep tropics system a 5 percent chance of developing into a tropical cyclone over the next ten days. Like the above system the National Hurricane Center has not mentioned this system on its tropical weather outlook.

We will have to keep watching the tropics this week. I will be back for another post tomorrow on these systems.