11:50 AM | *Weekend hurricane threat for Louisiana/Texas…recent changes in El Nino may have an impact on the remainder of the Atlantic Basin tropical season*
Paul Dorian
GOES satellite imagery features a strengthening area of low pressure over the Gulf of Mexico; courtesy NOAA, College of DuPage
Overview
Low pressure that pushed southward yesterday from Georgia to the northeastern Gulf of Mexico is now showing clear signs of strengthening and it is very likely to reach named (Barry) tropical storm status over the next day or two. While only slow intensification is expected for the next day or two, there are reasons to believe that the combination of favorable atmospheric and oceanic conditions will allow for more rapid strengthening beyond 48 hours and this could result in a category 1 or 2 hurricane this weekend over the Gulf of Mexico. A key player in the eventual path of soon-to-be named “Barry” will be a strong ridge of high pressure to the northwest that may steer this system towards a landfall Louisiana or Texas by the latter part of the weekend. In addition, with the building ridge to the northwest, there is the chance that this system becomes a slow mover and this will only enhance chances for some serious rainfall in the Gulf of Mexico region from eastern Texas to the western Florida Panhandle. Elsewhere, the centrally-based El Nino in the Pacific Ocean is now showing signs of weakening and this could result in a more active Atlantic Basin tropical season during the next few months.
Strong ridge to the northwest will be a key player in the eventual path and movement of what will be named “Barry”; courtesy NOAA/EMC, tropicaltidbits.com
Hurricane threat in the Gulf of Mexico
Low pressure dropped southward yesterday from Georgia to the northeastern Gulf of Mexico and it is now drifting over warmer-than-normal waters. Latest satellite imagery clearly shows a strengthening of this “home-grown” type of tropical system as it spins over the warm waters of the Gulf of Mexico. The next day or two will likely feature slow intensification only as there is still the lack of a well-defined center and some modest northerly wind shear in the region. Beyond that, however, wind shear is likely to diminish and quick intensification could be the result. As high pressure ridging strengthens in the upper part of the atmosphere later this week, there will be a tendency for “Barry” to push westward and it could move all the way to the central/western part of Louisiana before making a turn to the northwest and landfall. In fact, there is certainly the chance that the ridge of high pressure to the north becomes strong enough to push “Barry” even farther to the west resulting in a potential landfall over eastern Texas – still a few days away for this to play out. One final point of interest, the strongest Atlantic hurricanes on record (since 1851) to make landfall in the continental United States during the month of July were the “Gulf Coast Hurricane” of 1916 and Hurricane Dennis of 2005 - both had max winds of 120 mph at landfall (source: Philip Klotzbach, CSU).
Tremendous rainfall amounts are depicted by some computer forecast models (12Z Euro shown here) in the central Gulf coastal region and a strong ridge to the north supports this notion as movement is likely to be slow; courtesy ECMWF, weathermodels.com (Dr. Ryan Maue, Twitter)
In terms of rainfall, given the potential of slow movement as the ridge to the north builds this weekend, tons of rain can fall in southern Louisiana and all areas from eastern Texas to the western Florida Panhandle have to closely monitor this flooding threat. This type of system with this type of movement (i.e., slow) could result in some areas receiving 2 feet of rain by the time we get to the early part of next week; especially, across southern Louisiana and, keep in mind, the Mississippi River is already running at high levels due to excessive spring rains.
Current sea surface temperature anomalies are showing warmer-than-normal conditions in the Gulf of Mexico which will aid in the intensification of soon-to-be-named “Barry, a weakening El Nino in the central Pacific and a large pool of colder-than-normal water to the west of South America; courtesy NOAA, tropicaltidbits.com
El Nino
One of the key factors to the Atlantic Basin tropical season is the El Nino (warmer-than-normal) that has been consistent in the central Pacific for the past several months. It is, however, showing signs of breaking down; especially, on its eastern edge as a large pool of colder-than-normal waters is expanding to the west of South America. In addition, computer model forecasts are now supporting the idea of a weakening El Nino as we progress through the summer and this, in turn, could have an impact on the remainder of the still-young Atlantic Basin tropical season.
NOAA’s climate model (CVSv2) has weakened considerably from mid-June to now in its forecast of El Nino conditions in the “3.4” (central) region of the Pacific Ocean; courtesy NOAA
In a typical year when El Nino is strong in the tropical Pacific Ocean, the Atlantic Basin tropical season is usually below-normal. The reason for this is that El Nino conditions in the Pacific are usually correlated with increased wind shear in the tropical Atlantic and this is an inhibiting factor in tropical storm formation and/or intensification. If El Nino weakens or disappears, tropical activity could very well bump up during the rest of the Atlantic Basin tropical season.
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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