July Is Nearing End... - FLHurricane.com

This is just my opinion and isn't an official forecast...please read the disclaimer below.

My discussion from tropicalweatherwatchers.com...

FORECAST POSTED: 7/31/02/ 6:00 PM EDT

A lot going on in the tropics!!!

For the second straight day the models are hinting on tropical development in the Gulf of Mexico. Currently, we have a high pressure system at the surface. Buoy reports across the eastern Gulf of Mexico are indicating that the pressure in the area is between 30.00 and 30.05 inches. We need the pressure to drop down near 29.85 inches to be concerned. Now there have been pressure falls over the past few hours. However, we need the pressure to continue to slowly fall and persist for at least another 12 hours so that we can be sure that this isn't just a fluctuation. This is a big factor when it comes to the potential development of this low. If the doesn't weaken, the upper low will stay over land while moving westward, as a rain event. If the high does weaken as some of the models are predicting, then the low will move out into the open waters of the Gulf of Mexico and have a chance to develop.

There is some wind shear over the western Gulf. This is in response to an upper level low over Mexico. This low is moving west and will eventually move into the eastern Pacific Ocean. Therefore, the shear should begin to slowly diminish over the next few days.

Now I know a few people must be thinking, where is this low??? Well, we have an upper low over southern Georgia associated with a trough that extends all the way tot he upper low in Mexico. In addition, there is a much deeper trough move southeast out of the Tennessee Valley. Once these two troughs merge, we could see an area of low pressure develop over the eastern Gulf.

http://www.met.tamu.edu/newmodels/mrf500_H_SP_F132.gif

The MRF has a ridge moving east over the next few days. In 5.5 days, it shows the ridge centered over Missouri. Also, if you look closely near the Texas coast, you will see the low pressure system. The majority of the models are in agreement with this forecast. However, there are a couple exceptions...

Both The AVN and NOGAPS models take the low on a more northerly track.

http://www.essc.psu.edu/rhart-cgi-bin/avntc2.cgi?time=2002073112&field=950mb+Vorticity&hour=102hr

http://www.essc.psu.edu/rhart-cgi-bin/nogapstc2.cgi?time=2002073100&field=850mb+Vorticity&hour=096hr

Both models show the ridge to the north farther east, allowing a more southerly flow over the central Gulf states. These are the only models that take the low into the Gulf and then north between southeast Lousiana and Pensacola. The rest of the models are in good agreement with the low staying on a westerly track towards Texas with the ridge to the north. The westerly track seems more likely. It all depends on the speed of the ridge.

For the remainder of the Gulf of Mexico and Bay of Campeche, all is quiet. There is one tropical wave over the Bay of Campeche. But the wave is close to land and there are no signs of any organization taking place. The wave will move inland into Mexico sometime tomorrow.

There are no areas in the Caribbean Sea that pose any threat of developing into a tropical system. The vertical shear across the Caribbean has weakened greatly over the past 24 hours and the Tropical Upper Tropospheric Trough is basically nonexistant. However, as I stated yesterday, there is just too much sinking air over the area. In addition, the central Atlantic is covered in a pocket of subsidence, preventing any waves from moving into the Caribbean. The Caribbean Sea is shut down for development at least for the remainder of the week.

Now onto the upper low...

The chances of the upper low east of Bermuda developing are decreasing. The low center has been basically stationary for 24 hours. If we were going to get any development from this low, the movement would have been in a southerly direction...obviously this isn't happening. There is a trough to the northwest of the upper low. In 12-36 hours, the trough will begin to pull the upper low northward. The low should easily pass to the east of Newfoundland so no problems there. the low will impact the weather over Europe in about 7-10 days.

Remember the African wave?

The wave is still visivle on satellite and the models continue to show a decent sized wave moving off of the coast of Africa roughly in 72 hours. Yesterday, I mentioned how the upper low over the central Atlantic wouldn't give this wave much of a chance of development IF the upper low were to develop. Now there is a lot of sinking air and moderate vertical wind shear in the eastern Atlantic. Therefore, I don't believe that tropical development from this wave is likely. However, this could open the door for the Cape Verde season. Currently, the Inter Tropical Convergence Zone (ITCZ) is unusually quiet for this time of the year in the Atlantic. But once the wave emerges off the African coast, we should begin to see an increase in activity. This could be the start of the wave train. The Atlantic should get going in about two weeks.

Sea Surface Temperatures

Now don't be suprised to see the waters turn cooler again by the end of the day. However, the trend over the past two weeks have been gradual warming with some fluctuations...

http://152.80.49.210/products/OTIS/otis_glbl_sstanomaly.gif

http://www.cdc.noaa.gov/~gtb/tele/nao.gif

But the more important factor is the North Atlantic Oscillation. The NAO has turned negative. This means a stronger Atlantic thermohaline circulation within the next few weeks. In addition, long range forecast models are forecasting the Azores high to slowly weaken. What does all of this mean? Well if the forecasts do verifiy and the NAO stays negative long enough, we could see average to possibly even slightly above average ssts in some areas of the central and eastern Atlantic. But the ssts have been fluctuating a lot lately so we will just have to wait and see. Now if the sea surface temperatures do warm over the next week or so, that doesn't mean that they won't begin to cool once again. If the NAO goes back to a positive phase, we would go back to cooler ssts.

The ssts are still cooling in the EPAC. This has been going on for a while now and I am surprised about the longevity of the trends. If it weren't for the above average ssts in the central Pacific we would definitely be dealing with La Nina. This surely isn't a moderate or strong El Nino, and it doesn't even compare to the 1997 El Nino episode. Chances of El Nino having an impact on the season through November is highly unlikely. Don't let the media hype make you nervous.

Models show a few changes down the road

http://wwwt.emc.ncep.noaa.gov/gmb/STATS/maps/opnl/latest/f12.gif

http://wwwt.emc.ncep.noaa.gov/gmb/STATS/maps/opnl/latest/f180.gif

The 180H operational AVN model shows the 15 degrees celsius line in the central Atlantic much farther north than the 12 hour forecast. This means that the cooler subsiding air will likely begin to diminish, which will allow the ITCZ to move farther north. Bastardi also mentioned this a few days back. I also mentioned this on a few of the weather forums.

This also relates to the North Atlantic Oscillation forecasted to turn negative. The troughs over the northwest Atlantic stay farther north, allowing a ridge to build to the south. The NAO turning negative is a good sign that the tropics willbegin to heat up rather soon.

FORECASTER: Jason Moreland

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DISCLAIMER: THIS IS NOT AN OFFICIAL FORECAST. PLEASE LISTEN TO YOUR LOCAL NEWS OR THE NATIONAL HURRICANE CENTER FOR THE LATEST INFORMATION.

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