[Latest European model forecast of MJO index; "green line" represents the model forecasted daily movement of the MJO index through phases 2 and 3 during the period from May 29th to June 12th]
The official start to the Atlantic Basin hurricane season is this Sunday, June 1st, and there are some signs that there could be some early tropical activity to monitor. The Madden-Julian Oscillation (MJO) index is raising the possibility of tropical troubles in the Atlantic Basin during the early-to-middle part of June and this could ultimately have an impact on the east coast. The MJO index tracks a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days. The MJO has wide ranging impacts on the patterns of tropical and extratropical precipitation, atmospheric circulation, and surface temperatures around the global tropics and subtropics. Research has found that the location or “phase” of the MJO is linked with certain temperature and precipitation patterns around the world. The very latest MJO forecast by the European computer forecast model (see plot above) propagates the MJO index into phases 2 and 3 during the early-to-middle part of June and studies have shown that these two phases tend to be correlated with increased tropical activity in the Atlantic Basin.
Indeed, the last few GFS computer forecast model runs have been hinting at some possible development late next week in the western Caribbean Sea or southern Gulf of Mexico region (see forecast map below) and this potential tropical disturbance could ride up the eastern seaboard. In fact, the first named tropical system last year, Tropical Storm Andrea, formed during the early part of June in a period in which the MJO index passed through phases 2 and 3. That system developed near the Yucatan Peninsula region of Mexico, tracked across northern Florida, and then moved right up the eastern seaboard producing more than three and a half inches of rain in Philly on June 7th and 8th.
[GFS computer model forecast from yesterday for late next week showing a disturbance in the southwestern Gulf of Mexico with plenty of moisture; forecast map courtesy Weather Bell Analytics at weatherbell.com]