Tropical Update August 9th, 2008

Asia:

Just a few comments on the tropics in Asia. Currently there is a large trough just off the east coast of Japan, and the trough looks to continue for the next week in this region per the European model. This would hint at troughiness continuing along the eastern seaboard of the United States as well for the next 14-20 days! Conditions in Japan often coincide with conditions on the eastern seaboard of the United States in 7-10 day delay. Thus, the model forecasts of the trough starting to break down in the eastern United States might be a bit too bullish, and the troughiness might continue for some time. Which, in the long run, could be a good thing considering the more active hurricane period coming up.

Another note: No tropical systems are forecasted by the European model in Asia over the next 10 days at this time. This is good news for the Olympic games. Beijing isn't often directly impacted by a tropical system landfall considering they are so far north and a bit inland, but any remnants could impact the games with heavy rainfall. So, for right now, conditions look good for the coming up week to ten day period.

Tropical Atlantic:

Conditions are starting to look conducive for tropical development in the next 3-5 days through the end of the month. A conducive MJO is currently traversing across the central and eastern Pacific Ocean, and will move into the Atlantic in 7-10 days. This should lead to enhanced lift in the tropics, which will lead to more impressive tropical waves and more tropical development. El Nino is forecasted to stay neutral through the rest of the hurricane season.

Shear is currently low in the central Atlantic (5-20 knots), but is still high in the Caribbean Sea (30-50 knots). The GFS forecast over the next week forecasts shear to reduce in the Caribbean Sea, but the CMC does not. Strong shear looks to enhance just north of the preferred tropical wave trajectory path across the central Atlantic, but this shouldn't be a great hindrance to tropical development. If systems do move into this region, they wouldn't be a threat to the land anyway because they would be too far north to traverse across the entire Atlantic before moving north and out to sea.

Sea Surface Temperatures look conducive for development from the African coast all the way to the United States as long as systems stay south of 15N to 45W. Cooler temperatures are currently present in the southern Caribbean as well, but not cool enough to destroy a tropical system. Tropical Cyclone Heat Potential is most conducive for rapid intensification in the northwest Caribbean, the Bahamas, southeast Gulf of Mexico and in the extreme southern Atlantic near 10N, 40W.

So what are the models saying? The European, CMC, and GFS are all predicting tropical waves to start pushing off of the African coast in higher numbers in 7-10 days. The GFS predicts a current tropical wave in the central Atlantic to produce a tropical system in 3-5 days, which might be a bit too fast at this time. However, the wave is in a region of low shear, high sea surface temperatures, upper level divergence, has a reasonable cyclonic rotation, and decent convection. However, little lower level convergence is currently present and the system is still embedded in the ITCZ. If it can break away from the ITCZ it could have a chance at development, but the system is not too impressive just yet.

Beyond this system, little is currently active in the tropical Atlantic. The European, GFS, and CMC all predict an area of low pressure to develop in the central United States and move off of the southeast coast in the 3-5 day time frame. If the system is able to sit over the warm tropical waters of the gulf stream for a few days it could transition into a tropical system. But the models want to bring it quickly to the northeast and out to sea, which shouldn't allow it to develop. Further storm systems are predicted in the tropical Atlantic by all three models after 5 days, but none of these waves have moved off of the African coast just yet.