As the 2017 Atlantic hurricane season officially gets underway, we have our eyes on an area of the Gulf of Mexico which may see a tropical depression or storm form by this weekend or early next week.
Interestingly enough, this potential Gulf development may be helped, in part, by a remnant of another developing tropical cyclone off Mexico's Pacific coast.
Regardless of whether a Gulf tropical depression or storm develops, the threat of rainfall flooding will be in play along parts of the Gulf Coast into next week.
For now, clusters of thunderstorms are flaring in the western Gulf of Mexico.
The most vigorous convection is firing up off Mexico's Pacific coast, associated with newly-formed Tropical Depression Two-E.
What Does the Pacific System Have to Do With the Gulf?
The expectation is for the eastern Pacific Tropical Depression Two-E or Tropical Storm Beatriz to either move ashore in southern Mexico or fizzle near the coast later this week.
While it won't survive after its interaction with Mexico, some remnant upper-level energy and moisture from it may be drawn northward into the western Gulf by this weekend.
Sometimes these "ghosts" of a past tropical cyclone can give a bit of extra oomph in the atmosphere (lift, instability) to help a fledgling area of low pressure develop into a tropical depression.
This may be the case in the western or central Gulf of Mexico this weekend.
Will It Actually Develop?
As a matter of principle, clusters of convection over the Gulf of Mexico in or near hurricane season always should draw a meteorologist's attention.
While the number of June named storms in the Atlantic basin is small – typically only one named storm every 1 to 2 years – the large majority of June tropical storms and hurricanes since 1950 have formed in the Gulf of Mexico, often on the tail end of old surface fronts or troughs.
Over the years, the Gulf of Mexico has provided several examples of tropical storms, even hurricanes, that developed quickly.
One of these was Allison in early June 2001, which produced historic, billion-dollar flooding in the Houston metro area.
In this case, though, there are two negative factors that may work against a tropical depression or storm's formation:
1. Wind shear – the difference in wind speed and direction with height – is already high and isn't expected to slacken much. This may not allow thunderstorms to persist near the aforementioned surface trough long enough to begin the process of tropical depression formation.
2. Water temperatures in the northwestern and northern Gulf of Mexico are actually a bit cooler than average for this time of year. This may cut down slightly on instability to continue to fuel thunderstorms near any prospective areas of low pressure in that part of the Gulf.
Therefore, the chance of development of a depression or storm appears to be low, for now. The next name on the Atlantic list is "Bret." Just over a month ago, "Arlene" was only the second April Atlantic tropical storm in the satellite era.
One Threat, Regardless of Development
Despite the low chance of a tropical depression or storm, the overall atmospheric setup into next week poses a threat of heavy rain and flash flooding near the Gulf Coast and Florida Peninsula.
There's a host of ingredients in play to raise the flash flood threat.
1) A deep flow of tropical moisture pushing toward the Gulf Coast
2) A slow-moving upper-level low over Texas adding instability to the atmosphere
3) An arriving frontal boundary, providing a focus to lift the warm, humid air
4) A sharp jet stream plunge into the East, which may induce an area of low pressure to form along the front, further focusing heavy rain
Repeated rounds of locally heavy rainfall are possible this weekend into next week from the upper Texas coast to the Florida Peninsula.
With the ground already saturated over much the northern Gulf Coast, the threat of flash flooding there is high.
While the weather pattern isn't the same this time, remember the multi-billion-dollar flood event in Louisiana last August wasn't officially accompanied by even a tropical depression.
However, while some localized flooding is also possible in the Florida Peninsula and southern Georgia, this rain is also needed, given the current severe to extreme drought and recent wildfires.