12:00 PM (Thursday) - ***”Caribbean Sea-to-Gulf of Mexico” tropical storm threat continues for later next week as changing weather pattern will result in enhanced upward motion***
Paul Dorian
The tropical disturbance feature known as the Madden-Julian Oscillation will rotate into Phases 7 and 8 in coming days (counterclockwise direction on plot) which is a more favorable location for tropical storm activity in the Atlantic Basin. Map courtesy NOAA, ECMWF
Overview
The atmosphere is about to undergo a significant change over the Caribbean Sea and Gulf of Mexico which will result in enhanced upward motion in that part of the Atlantic Basin and this, in turn, increases the chance for the development of a hurricane later next week. The change in the atmosphere is largely the result of the re-positioning of a tropical disturbance that propagates eastward along the tropics on a regular basis. This undergoing pattern change with enhanced upward motion in the Atlantic Basin may, in fact, result in additional tropical activity that takes us passed this initial threat and well into the month of October.
This forecast map by the ensemble run of the Euro is for the current week that runs through September 21st and it features upper-level convergence in the atmosphere (circled region) over the Gulf of Mexico and Caribbean Sea. Upper-level convergence leads to compensating lower-level divergence which acts as an inhibitor to large-scale upward motion and this has been acting as a "cap" on tropical activity....that "capping lid" comes off next week. Map courtesy ECMWF, Weather Bell Analytics
Madden-Julian Oscillation (MJO)
Meteorologists track an oceanic-atmospheric phenomenon known as the Madden-Julian Oscillation or MJO which affects weather patterns across the globe. Unlike El Nino or La Nina which are stationary features in the equatorial Pacific Ocean, the MJO is an eastward moving disturbance of clouds, rainfall, winds and pressures that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average. The MJO was first discovered in the early 1970s by Dr. Roland Madden and Dr. Paul Julian when they were studying tropical wind and pressure patterns.
This forecast map by the ensemble run of the Euro features upper-level divergence in the atmosphere (circled region) for next week (September 22nd to September 29th) over the Gulf of Mexico and Caribbean Sea. Upper-level divergence leads to compensating lower-level convergence which, in turn, enhances upward motion. This upcoming change to the overall weather pattern could result in a significant tropical storm threat in the Caribbean Sea/Gulf of Mexico later next week. Map courtesy ECMWF, Weather Bell Analytics
The MJO consists of two parts or phases with one being the enhanced rainfall (convective) phase and the other being the suppressed rainfall phase. The location of the convective phases is often grouped into geographically based stages that are numbered 1-8 by scientists. The location or phase of the MJO can be tied to specific weather patterns in different parts of the world depending on the time of year. The MJO creates favorable conditions for tropical cyclone activity which is why it is important to monitor during the Atlantic Basin tropical season. The last 30-day time period has generally been unfavorable for tropical activity in the Atlantic Basin with respect to the positioning of the MJO; however, the next month is looking more favorable. Specifically, with the re-positioning of the MJO, upward motion is soon become significantly enhanced across the Caribbean Sea and Gulf of Mexico and there may be increased tropical activity in much of the Atlantic Basin going into the month of October.
With the enhancement of the upward motion during the next several days, look for possible tropical storm development somewhere over the still very warm waters of the northwestern Caribbean Sea with possible movement to the Gulf of Mexico in following days. With this scenario still many days away - and no actual systems yet on the map in the Caribbean Sea or Gulf of Mexico - details will have to wait to be ironed out; specifically, in terms of the potential storm’s track and magnitude. However, given the evolution of the overall weather pattern to much more favorable in the Atlantic Basin, it is certainly safe to say from this vantage point to “stay tuned”; especially, for residents across the Gulf states.
Water temperatures are still quite favorable across the Gulf of Mexico and Caribbean Sea for the formation and intensification of tropical cyclone activity. Map courtesy NOAA, tropicaltidbits.com
Meteorologist Paul Dorian
Arcfield
arcfieldweather.com
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