Since I'm off most Fridays, I get to review most of the other channel's weather programs. The words I kept hearing were...non-tropical...referring to the upper low over the eastern Gulf. I wondered, how many people know what that means? Better yet, why is it important? Here's my analogy. Think of a cubic foot of air that has many molecules in that space at say 60 degrees. Now let's heat that cubic foot to 90 degrees keeping the same pressure. The cubic foot would now expand to say a cubic yard since the heated molecules get more excited and need more space.(pressure doesn't change) What happens though is the relative humidity drops since there is now more space. Bottom line...warmer air has a greater capacity to hold moisture(water vapor). Non-tropical refers to a system that has a cold core the higher up you go. Tropical refers to a warm core system. That's the important difference as a Tropical Low has a much greater potential to produce flooding rains vs. a non-tropical system. Sometimes a non-tropical system can become tropical over time IF it stays over warm water long enough.
At the noon hour, satellite loops are showing a well defined circulation over the Gulf south of PNS/MOB. It is moving westward rather quickly. In addition, upper winds are strong out of the north and that is why NHC gives this system a low(10%) chance to develop. Once to our west, we'll get on the wet side of the low and rain chances go up for late Sunday into Monday.
2 comments:
Not too concerned about the low in the Gulf either, Bob. Its a big decoupled baroclinic(non-tropical) mess. I don't presently see it doing much and if it does do something other than increase our winds and rain chances I will let y'all know.
Now regarding the developing disturbance in the SW Caribbean which will quickly steal the show by Monday....
Satellite imagery along with MIMIC TPW, and CIMSS vorticity products indicate that a long anticipated tropical disturbance has begun to develop in the Southwestern Caribbean Sea with broad cyclonic turning noted south of Jamaica or at approximately 16N 78.5W. This disturbance, soon to be declared 96L, is embedded in an envelop of deep moisture. In addition, the disturbance is in a very low shear environment thanks to a broad upper-level anti-cyclonic circulation aloft which will ventilate it. Soon to be 96L is also in a widespread area of 28-30C waters. Due to the aforementioned parameters in place along with strong model support from the ECMWF, GFS, GFSP, CMC, NAM, DGEX, SHEF, ECMWF ensembles, and CMC ensembles a tropical depression is likely to develop in the next 2 days with a high chance of an eventual upgrade to tropical storm status. 96L is being steered by sub-tropical high pressure to its north and will be throughout its lifetime. All interests from Houston, Texas to Tampico, Mexico need to keep a close eye on the wear-abouts of this potential system.
-ONLYREAL
Good evening everyone,
95L remains south of our coast this evening and remains weak. I don't see this causing any problems other than increasing our rain chances.
96L on the other hand is a bigger threat. Visible and Infrared satellite imagery clearly shows that the tropical disturbance is getting better organized. Water Vapor imagery shows a very low shear environment over 96L with clock-wise turning which indicates the presence of an upper level anti-cyclone. It should be noted that the origins of this disturbance is NOT from a tropical wave, but from an area of piling heat and moisture which has caused pressures to lower. This type of pattern is how typhoons form in the west Pacific. The tropical wave moving through that area is just a visitor and can only act as a catalyst for the formation of a low-level circulation. Anyway, the Hurricane Hunters are heading out to investigate 96L tomorrow and will likely find a Tropical Depression, maybe even a Tropical Storm considering 2 ships near 96L's center reported tropical storm force winds. Now I would like to bring to everyone's attention that a Mexican landfall has become much less likely and a Texas or even Louisiana landfall is becoming much more likely. With upper level conditions look to be favorable for strengthening and a strong tropical storm or even minimal Hurricane landfall looks to be the case with this system along the Gulf coast on Wednesday/Thursday.
Also, the tropical wave near the lesser Antilles looks poised to develop and will be soon labeled 97L. This will need to be watched for trouble down the line.
-ONLYREAL
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