Talking the Tropics With Mike: Strengthening hurricane Laura headed for Texas/Louisiana... Marco dissipates

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LOCAL - JAX/NE FL./SE GA. impacts from Laura: ** None directly ** ... but folks traveling or who live anywhere along the Gulf Coast from Florida’s Western Panhandle to Texas - need to stay up to date on future forecasts regarding the tropics as fast changes/development will be possible this week. The swift northward movement of Laura will mean a threat well inland with wind, isolated tornadoes & very heavy rain/flash flooding.

LAURA:

The 4th Atlantic hurricane of the 2020 season - only 7 other seasons have had as many hurricanes by Aug. 25th - 1886, 1893, 1916, 1966, 1995,1996 & 2005 - Laura is - as expected - the big story coming out of the Gulf as the storm now has plenty of warm water to cross under favorable (atmospheric) conditions to strengthen through midweek before reaching the Western Gulf Coast Wed. night-Thu. Models have been pretty stable with a landfall pretty close to - a little west of - where Rita came ashore in 2005, but the expanding Bermuda High still keeps Texas (vs. Louisiana) as a spot for a potential landfall. This is a very close call for Houston & Galveston. A track over or near oil wells & the petroleum facilities could mean a “bump at the pump” over the next week or two as well.

There will be plenty of significant impacts for Louisiana too & - at least to some degree - for coastal Mississippi & Alabama as well.

Strong tropical wave ’98-L’ was upgraded to tropical depression #13 Wed. then to tropical storm “Laura” Fri. while steadily moving west & across or near Puerto Rico, Hispaniola & Cuba... reaching hurricane strength Tue. morning over the Southern Gulf of Mexico. This is the fastest to the 12th storm breaking the record of “Luis” on Aug. 29, 1995. As the Bermuda High to the north expands & strengthens, Laura should continue a steady track west before a slow bend to the northwest & forecast models are in excellent agreement on such. This takes Laura away from Cuba followed by a 2-day track across the Gulf of Mexico. There remains a reasonable chance - as has been the case for days now - for a track farther west as the Bermuda High flexes its muscles (helping to protect Jacksonville/NE Fl./SE Ga). Despite land interaction & moderate shear out of the north, satellite & radar data still show an organizing tropical cyclone with upper level outflow evident over the top of the storm. Given the strengthening already underway & the presence of good upper level outflow combined with less shear, Laura may fairly quickly strengthen once over the Gulf of Mexico Tue.-Wed. with a period of rapid intensification possible. As has been the case since its inception last week, I’ve been concerned about a “late bloomer” on this one.

As Marco dissipates near the Gulf Coast, it looks like the alleyway to the Gulf opened up by a departing/weakening upper level trough will pretty quickly close as an extension of the sprawling Atlantic Bermuda High builds to the west. This turn of events is likely why forecast models have trended west in what will be a major hurricane threatening Texas &/or Louisiana mid to late week. The shear that hammered Marco to the north will not be an issue until approach to land which will likely be too late to have much of a detrimental impact on Laura, especially given the relatively fast movement. The models are locked in on timing for the most part - Wed. night into early Thu. for a landfall... & pretty much all of the models show some form of strengthening if not major intensification through midday Wed.

MARCO:

Tropical wave ’97-L’ has turned rather sharply to the north after entering the Caribbean Mon. night & was upgraded Thu. morning to tropical depression #14 & then to tropical storm “Marco” Fri. evening & briefly to a hurricane Sunday afternoon before being downgraded again to a tropical storm by evening... a depression by Mon. evening... & a remnant low during the final NHC advisory early Tue . Landfall was on the SE tip of Louisiana at the mouth of the Mississippi Mon. evening about 7pm EDT. Marco missed most of the potential land interaction with the Yucatan Peninsula over the weekend which allowed for short term strengthening but shear out of the SW is strong (25+ mph) & continue to pound & consequently weaken Marco. The cyclone was effectively “decapitated” Sun. night as the low level center churned southeast of New Orleans while a mid level center was to the northeast with all the heavy rain & gusty winds.

There was quite a bit of scuttlebutt regarding a possible “Fujiwhara effect” between Marco & Laura of which the First Alert Weather Center never was a part of, & it’s obvious now why that was a good route to take (tropical cyclone Fujiwhara effects have happened in the past, by the way). In any case.

Overall conditions across the Atlantic Basin appear “ready to go” as we move through late Aug. & early Sept. (see velocity potential anomalies map below). I’m also tracking a potential long track tropical disturbance soon to move westward across the Atlantic that could threaten some part of the U.S. between ~Sept. 3 & Sept. 9th.

CIMMS Integrated Microwave Imagery showing nicely the organizing/strengthening of Laura:

Spaghetti plots:

Rainfall forecast.... with very heavy rain extending well inland due to the swift movement of Laura not to mention a tornado threat:

A change of phase of the MJO (Madden-Julian oscillation) should help lead to an uptick in Atlantic tropical cyclones late this month into September. The upper level “velocity potential anomalies” map below shows “upward motion” - green lines - spreading east from the already active E. Pacific. Such a pattern often correlates to an increase in tropical systems that would eventually include the Atlantic Basin.

A strong tropical wave over the far Eastern Atlantic is marching west....