It is Friday, and as always, that means it is time to take a look at the Atlantic! The Atlantic basin remains mostly quiet for the moment, with no active tropical cyclones or investigative areas. The National Hurricane Center (NHC) is not anticipating any development over the next five days. However, several recent runs of the GFS model and its ensembles have been indicating the possibility of development of a tropical wave in the central tropical Atlantic during the next week or so. No other models are currently predicting development of this system, and a suppressed phase of the Madden-Julian Oscillation (MJO) will likely limit development. Let’s take a look at the current state of the Atlantic basin.

Sea Surface Temperatures

The 26°C (78.8°F) sea surface temperature (SST) isotherm – the typical threshold for tropical cyclone development – continues to expand and now covers most of the Atlantic basin where tropical cyclones develop. It has expanded as far northeast as Cape Verde in the eastern tropical Atlantic, and as far northwest as Northeastern North Carolina. Most of the Atlantic MDR, Caribbean Sea and Gulf of Mexico now has SSTs of 27-28°C (80.6-82.4°F). The warmest sea surface temperatures in the Atlantic basin – 29-30°C (84.2-86.0°F) – are located in the Bay of Campeche. As noted in yesterday’s post on the Atlantic Multidecadal Oscillation, SSTs in the Atlantic MDR and subtropical western Atlantic are above average for the time of year. SSTs in the Caribbean Sea are slightly above average for the time of year – a departure from last season, in which they were well above average. SSTs in the Gulf of Mexico are near to slightly below average.

Wind Shear

Atlantic wind shear continues its slow decrease from May through September. Wind shear in the Atlantic basin as a whole has been slightly below average, which is usually an indicator that an above average season is ahead. Wind shear has been especially lower than normal in the Atlantic Main Development Region (MDR), averaging about 10 knots less than normal from the May 28 to June 26 period. Wind shear in the eastern Caribbean Sea has been slightly above average, and wind shear in the western Caribbean Sea has been slightly below average. Wind shear has been above average in the Gulf of Mexico. The significantly lower than normal wind shear in the Atlantic MDR likely aided in the rare and early genesis of Tropical Storm Bret 11 days ago. This lower than normal shear could be a positive factor for a tropical wave in the far eastern Atlantic, which the GFS model and some of its ensembles have been predicting development (see below).

African Tropical Waves

The African tropical wave “train” has quieted down this week after being very active for most of the month of June. This is largely due to the departure of the favorable phase of the MJO from Africa. A tropical wave in the eastern Atlantic with an axis extending from 03°N 27°W to 12°N 25°W has to be watched for development, based on recent GFS runs. The 12z Friday GFS run develops this wave into a weak tropical cyclone by late next week as it travels northwestward into the central Atlantic Ocean. However, no other models predict development – likely due to the suppressed MJO phase. The NHC has not mentioned this system on its tropical weather outlook. Another weak tropical wave is located over west Africa, but no models predict development of this wave.

Tomorrow is July 1, so I will be back tomorrow for a post on the history of July tropical cyclones in the Atlantic, so you know what to expect for the month. It will analyze statistics for the month and take a look at some of the most significant Atlantic hurricanes to form in the month of July.