Thursday, September 10, 2015

Tropical Development Is Possible in Western Gulf of Mexico Next Week

Jon Erdman
Published: September 10,2015

During the heart of the hurricane season, each and every disturbance deserves due diligence.
If the environment isn't too hostile, a cluster of thunderstorms near a fledgling area of low pressure can quickly develop into a tropical depression or tropical storm.
If this occurs near land, a forecast mentioning more typical passing showers may evolve into a threat of coastal flooding, high surf, strong winds along with rainfall flooding.
With that in mind, we're keeping an eye on an area, but are not too concerned about development just yet. Here's what we're watching and what may keep this system from developing.
Mid-September origin points of tropical cyclones in the Atlantic Basin. The western Gulf of Mexico is just one of many possible hot spots this time of year.

Common Pattern With A Pair of Potential Inhibitors

Computer forecast models may struggle at times with critical, small-scale details of the weather beyond, say, five days or so.
Therefore, meteorologists look for overall patterns in surface weather features and those at jet-stream level in longer-range periods to help identify potential weather hazards ahead.
One such pattern that may set up next week has captured the interest of meteorologists.
Namely, the leftover of a cold front – often just a zone where surface winds converge with an increasingly vanishing temperature contrast – will drape over the Gulf of Mexico. Meanwhile, a broad area of low pressure, or trough, may orient itself in a north-south fashion over the western Gulf of Mexico.
If thunderstorms can concentrate near an area of low pressure, it's conceivable a tropical cyclone could spin up in the western Gulf of Mexico next week.
Potential atmospheric setup in the Gulf of Mexico in the week ahead.
However, one familiar inhibiting factor may be in play.
The same forecast guidance showing surface low pressure in the western Gulf of Mexico is also indicating appreciable west winds aloft over parts of the western Gulf may continue.
This difference in wind speed and/or direction with height, known as wind shear, typically weakens existing tropical cyclones and can inhibit new tropical cyclones from forming.
One other potential negative factor for development is if the disturbance ends up moving over land in western Mexico before it has the chance to development over the Gulf of Mexico.

One Threat Regardless

Regardless of development, the potential for heavy rainfall is in play for parts of the western Gulf Coast next week.
"The details of tropical cyclone development or lack thereof have been variable from model to model and run to run," said senior meteorologist Stu Ostro. "However, there's been a consistent, solid signal for an area over eastern Mexico and the western Gulf of rising air, low pressure, and heavy rain."
Together with high pressure centered over the eastern U.S., a pipeline of deep moisture may target the western Gulf Coast states next week with bands of locally heavy rainfall.
(FORECAST: Corpus Christi | Houston | New Orleans)
Where these bands persist, flash flooding would quickly result, with rain rates of 3-inch-per-hour or more possible, at times.
(MORE: Danger of Your Vehicle in a Flash Flood)
Check back with us at weather.com and The Weather Channel for the latest on this forecast.

MORE: Hurricane Strikes by County, Parish

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