Talking the Tropics With Mike: Marco falling apart... Laura: the main “attraction”

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LOCAL - JAX/NE FL./SE GA. impacts from current tropical activity: ** None directly ** ... but folks traveling or who live anywhere along the Gulf Coast from Florida’s Panhandle to Texas - need to stay up to date on future forecasts regarding the tropics as fast changes/development will be possible this week.

Any local impacts from Laura look to be relegated to a slight bump in waves & surf through Tuesday & a bit of a surge of tropical moisture from the east increasing rain slightly. No significant direct local impacts are anticipated while current tropical cyclones take the “low road” - Marco far to the west & Laura well to the south then far to the west.

According to Phil Klotzbach, “hurricane guru” @ CSU, this could be only the 3rd time since 1851 that there have been simultaneous Gulf of Mexico storms with winds 39+ mph (tropical storm strength): Sept. 5, 1933 & June 18, 1959 (especially impressive - early season!) though it’ll be close on whether or not Marco is still kickin’ when Laura officially enters the Gulf Tue.

LAURA:

Laura will be the true “problem child” as the storm will have plenty of warm water to cross under favorable (atmospheric) conditions to strengthen in the coming days before reaching the Gulf Coast mid to late week. Models have been trending west recently & Texas may end being landfall though it’s still early on how steering currents will exactly play out. 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. 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 keeps the cyclone near the south coast of Cuba into Mon. evening. There remains a reasonable chance - as has been the case for days now - for a track farther south & 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 a relatively well organized cyclone with upper level outflow evident, especially over the southern half of the circulation. The center may very well jump around some until the cyclone is away from land & better organized with weakening shear. Given the the current state & the presence of good upper level outflow combined with less shear, Laura may fairly quickly strengthen once over the Gulf of Mexico Tue.-Wed.

As has been the case since its inception last week, I’m still concerned about a “late bloomer” on this one. A tropical cyclone that’s relatively weak until making it into or near the Gulf of Mexico by Tuesday. Once in the Gulf & away from any land areas, there should be a gradual turn more northward. There will be heavy squalls into Monday night for Cuba with a distinct threat for flash flooding & landslides.

As Marco weakens 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 could be a major hurricane threatening Texas &/or Louisiana by mid to late week. The models are locked in on timing for the most part - later Wed. into early Thu. for a landfall... & pretty all of the models show some form of strengthening. The GFS is not as intense & a little more east.... the UKMET is off the charts with a major hurricane (& a little more west which would up the ante for Texas)... & the European is in-between.

MARCO:

Tropical wave ’97-L’ has turned rather sharply to the north after entering the Caribbean Mon. night & has been upgraded - as of Thu. morning - to tropical depression #14 & then to tropical storm “Marco” Fri. evening & briefly to a hurricane Sunday afternoon before being downgraded again. Marco - a compact tropical cyclone - has been slowing some & turning more northward as it gets to the western edge of the now sprawling Bermuda High over the Atlantic & is following a weakness in the flow helped out by an upper level trough. Marco missed most of the potential land interaction with the Yucatan Peninsula which allowed for short term strengthening but shear out of the SW is strong (25+ mph) & should keep Marco “in check” overall &, in fact, effectively “decapitated” the storm Sun. night with the low level center churning southeast of New Orleans while a mid level center was to the northeast with all the heavy rain & gusty winds. We’ll likely see continued bursts of heavy thunderstorms into Mon. night/early Tue. Virtually all of the heavy rain & wind will be in the north & east quadrant due to the persistent shear with flooding & isolated waterspouts/tornadoes being the primary threats from the Fl. Panhandle to near New Orleans. As the Bermuda High builds to the west & Marco weakens, the decaying center should turn more to the west with time.

There has been quite a bit of scuttlebutt regarding a possible “Fujiwhara effect” between Marco & Laura. I still see the two systems remaining their own separate entities, so I’m not going there. In fact, it’s arguable whether or not Marco will still be a “thing” as Laura starts to dominate the Gulf (tropical cyclone Fujiwhara effects have happened in the past, by the way). In any case... no need for a lot of hype(!) or concern on this possibility.

Overall conditions across the Atlantic Basin appear “ready to go” as we head into 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. 1 & Sept. 9th.

Lots of spaghetti(!):

Lots of rain along & near the Gulf Coast this week due to a combination of tropical activity & an upper level trough with extreme rainfall possible from the upper Texas coast to the Central Fl. Panhandle:

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....