Friday, July 2, 2010

Invest 95L near Florida panhandle

As we enter the month of July, a big question on the mind of meteorologists is, how active will the tropics be?

Atlantic ocean sea surface temperatures continue to be well above normal, even above 2005 levels. And as a la nina takes over in the equatorial Pacific, westerly shear is overall below normal across the Atlantic. In addition, intrusions of dry air from the Sahara have been limited. These three main factors are all positive for a very active, possibly historic hurricane season. This is nothing new; there's been a strong consensus since the spring for such a possibility.

June is officially the first month of the Atlantic hurricane season and on average only produces a tropical cyclone every few years. Historically it has practically zero correlation to the total season activity. June 2010 was relatively active however, producing Hurricane Alex, the strongest June hurricane in the Atlantic since 1944.

Now onto July, the correlation between monthly activity and total season activity becomes a little stronger. Just think back to 2005, when a record breaking five tropical storms formed, three of which were hurricanes, with two major hurricanes. These numbers obviously gave some foreshadowing to the rest of the record breaking season.

Currently in the Atlantic, there are no monster tropical systems in the making, just a few disturbances to discuss. First and foremost, we have a new invest, 95L just south of the Florida panhandle near 29N/85W. The low is left behind from the trough currently moving offshore (see "heat wave" post), and is nontropical at this time. The is moderate shear and dry air affecting the system, with any thunderstorm activity confined to the south of the circulation. Model guidance brings 95L west and then turns it northwest into Louisiana as a shortwave dives into Texas. At this time, no significant tropical development is expected, but periods of rain and some gusty winds may impact the central Gulf coast within the next four days.

One other noteworthy disturbance is located in the south central Caribbean near 12N/75W. Scattered moderate showers and thunderstorms have been associated with a weak circulation, moving slowly westward. The NAM organizes this tropical wave in the western Caribbean over the next three days. Given a moist, low shear environment, the potential does exist for some slow development. If still in tact, the wave could move into the Bay of Campeche by next weekend. The BoC is often a breeding ground for quick developing tropical storms, so this wave may need to be watched.

Lastly, there is moderate convection associated with a tropical wave near 10N/50W. Most of the convection is within the ITCZ, and no short term development is expected.

Elsewhere across the Atlantic, a strong upper level trough can be seen on water vapor imagery along 60W. This trough is generating strong vertical shear from the NE Caribbean into the central Atlantic.

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