I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.
By: KoritheMan , 7:50 AM GMT on October 10, 2012
A vigorous tropical wave over the central Atlantic located about 750 miles east of the Windward Islands is producing a large area of showers and thunderstorms.
Figure 1. Latest infrared satellite image of Invest 98L. Image credit: NOAA
While the shear is not prohibitively strong yet, water vapor imagery suggests that southwesterly shear lies just ahead. The GFS suggests a small anticyclone will try to establish itself atop the low-level center during the next 24 hours, but I question the authenticity of this. The wave and its embedded low pressure center only have about another 12-24 hours before the shear increases. After 72 hours, there is no unity between the GFS and the SHIPS, with the latter model indicating that a ginormous shear wall will prevent 98L from developing. The former, which experience has shown to generally be more reliable, suggests that the shear may lessen a little as the system approaches the Leeward Islands. How favorable the environment becomes as the tropical wave approaches the islands is strongly contingent on how the system interacts with the mid-oceanic trough; a scenario where the tropical wave axis moves closer to the upper-level trough would obviously result in a much higher magnitude of vertical shear, while a situation where the low is equidistant to the trough would result in a more diffluent, less sheared upper wind pattern.
The track models are fairly unified in tracking the system into the northern Leeward Islands in the next 4 - 5 days. After that time, the guidance becomes a little divergent, but in general, they suggest that a strong upper-level trough forecast to amplify over the western Atlantic will be sufficient to recurve 98L well east of the United States. This would tend to fit the climatological motif for a storm forming in this area of the world during the middle of October. However, fairly strong hurricanes can still develop in the eastern Caribbean this late in the year, as most recently demonstrated with Hurricane Tomas in 2010. While I doubt 98L will become another Tomas, interests in the Leeward Islands should monitor its progress, as if the GFS is correct, the upper-level environment could become a little more favorable for development as the system approaches the archipelago; this scenario would potentially place an intensifying tropical cyclone in the vicinity of Puerto Rico and the northern Leeward Islands.
Regardless of development, this system is expected to produce heavy rainfall and gusty winds across much of the Lesser Antilles beginning in about 3 days. These rains could cause flooding in some areas.
Probability of development in 48 hours: 20%
An area of disturbed weather has developed several hundred miles south of the coast of Mexico. Upper-level winds appear favorable for slow development of this broad disturbance over the next couple of days as it moves generally westward.
The majority of global models develop this low into a tropical cyclone in about 3 - 5 days, and then show a possible threat to Baja.
Probability of development in 48 hours: 10%
Comments will take a few seconds to appear.