Tropical weather analysis - June 17, 2011

By: KoritheMan , 4:42 AM GMT on June 18, 2011

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Invest 92E

Invest 92E has gradually become better organized today. Satellite loops reveal that the surface circulation associated with this broad low pressure area is better defined than this time yesterday, with low cloud motions indicating that the overall circulation is becoming tighter.



Figure 1. Latest infrared satellite image of Invest 92E, courtesy of NOAA's Satellite Services Division (SSD).

The synoptic environment in which this system is embedded is one characterized by light northeasterly to easterly shear. This light, diffluent shearing regime is forecast to give way to an anticyclonic environment over the next day or so, which should persist until late Sunday or early Monday. Once the system loses its anticyclone, it will encounter a more solid easterly to southeasterly upper tropospheric wind flow, which, when combined with land interaction, may induce some gradual weakening after that time.

All things considered, yesterday's thoughts have not changed: I still expect this system will become a tropical depression tomorrow night. In reverence to the solution of the models in regards to the intensity, I will peak this system at 55 kt (65 mph) in 72 hours. However, due to inherent uncertainties present in intensity forecasting, this system could easily become a hurricane.

The track forecast, as always, is far easier than trying to project the intensity of this meteorological marvel. Water vapor imagery shows large scale troughing continues to dominate the western United States, with a slight southward migration of the central United States ridge as this troughiness slides up along the western periphery of this ridge. A weakness in the ridge is evident near 100W, so 92E should turn west-northwestward late tomorrow. In the meantime, a continued westward motion, possibly just north of due west, can be anticipated. I still think the trough is sufficient to bring 92E dangerously close to the southwest coast of Mexico sometime on Tuesday. Indeed, most of the models have moved more poleward today, reflecting this very real possibility.

Due to uncertainty in the precise amplitude and timing of the trough (and thus the sharpness of the projected poleward turn), along with a nod to some of the models that keep the system offshore, my own forecast runs the system roughly parallel to the coast over the next several days, with a turn toward Sinaloa at day five.

Interests along the coast of Mexico should carefully monitor the progress of this system over the next several days. I imagine that the National Hurricane Center will be quick to issue tropical storm watches and/or warnings for a portion of the southern and southwestern coasts tomorrow or Sunday.

Regardless of development, locally heavy rainfall may affect portions of the southern coast of Mexico over the next day or two. These rains could eventually overspread portions of the southwestern coast with time.

Elsewhere

Elsewhere in the tropics, the global models predict that a large, monsoonal area of disturbed weather will form in the Bay of Campeche over the next 5 - 7 days. The GFS is less aggressive with this system as of the 0z run, possibly due to it remaining in closer proximity to the Mexican coastline, but it allows it to fester over the Bay of Campeche for days, becoming a large monsoon system with prodigious rains. These types of systems are not uncommon in the Bay of Campeche if the systems in question are given enough time to meander: Tropical Storm Frances in 1998 and Hurricane Isidore in 2002 are two examples that immediately spring to mind.

Regardless of development and the eventual track of this system, it does appear that portions of drought-stricken Texas, from the Texas/Mexico border northward to Galveston may finally get some much needed rainfall, as tropical moisture associated with this system gets drawn northward by persistent troughing along the west coast.

I still think this system has the potential to come northward and make landfall along the Texas coast, but it would be foolish for me to posit absolutes, especially for a system that hasn't even reared its head yet.

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1. weatherganny
4:06 PM GMT on June 18, 2011
Very Nice and informative...thank you!!
Member Since: August 8, 2008 Posts: 0 Comments: 220

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About KoritheMan

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.