Talking the Tropics With Mike: Laura far inland & weakening

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LOCAL - JAX/NE FL./SE GA. impacts from Laura: ** None ** ... but one of the strongest landfalling hurricanes in Louisiana’s history &, in fact, for any of the Gulf Coast. The swift northward movement of Laura will translate into a threat well inland with wind, isolated tornadoes & heavy rain/flash flooding.

LAURA ** A catastrophic landfall for the Central & SW Louisiana Coast **:

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 crossed warm water under favorable (atmospheric) conditions to allow for steady & then rapid strengthening through Wednesday evening before reaching the Western Gulf Coast in the wee hours of the morning Thu. Landfall was east of the Sabine River about 30 miles south of Lake Charles at Cameron, LA about 1:50am EDT sparing the major metropolitan areas of Houston & New Orleans. The area is not highly populated but early indications are that virtually any & all homes/businesses were destroyed where the eyewall came ashore.

This is the first “major” (Cat. 3+) hurricane over the Gulf since Michael in Oct., 2018 (Fl. Panhandle) & the first in *August* since Harvey in 2017 (Texas coast & almost 3 years to the day). Laura will be the 7th named storm to hit U.S. soil this season so far - a record for the number of hits before the end of Aug. (1886 & 1916 had 6 U.S. landfalls)

The relatively fast movement is allowing Laura to maintain tropical characteristics & some intensity well inland with with a wind, tornado & flooding threat north into Arkansas & SE Missouri then bending east across parts of Tennessee & Kentucky.

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 the a “major” Cat. 3 hurricane Wed. morning & a Cat. 4 Wed. afternoon - an increase in winds of 75 mph in less than 24 hours & appears to be the fastest intensifying in the Gulf on record! This is also the fastest to the 12th storm breaking the record of “Luis” on Aug. 29, 1995. With the strong Bermuda High to the east, Laura will turn more northward through Thu. then northeast into Arkansas & SE Missouri where there will be a sharp turn to the east as the jet stream “catches” Laura to the north of the Bermuda High. There was an increase in shear &, of course, friction upon approach to land but the size, organization (steady state), intensity & speed of Laura offset most of the negative effects keeping Laura severe/”steady state” - a high end Cat. 4 - upon the hit on the SW Louisiana coast. The storm moved nearly 300 miles inland in just 16 hours after landfall.

The tropical cyclone will move quite quickly N/NE before bending rather sharply to the right Friday. Such a track would imply severe weather - wind/rain/tornadoes - all along the track from Arkansas to the east coast with possible redevelopment of a tropical cyclone once offshore of the Mid Atlantic states over the Western Atlantic Sunday *but* while moving away from the U.S. over the NW Atlantic. The alternative end game is becoming absorbed by a large nontropical low over SE Canada & the NW Atlantic. In any case... the jet stream is rather strong for this time of year across the mid & northern latitudes of the U.S. so as Laura gets caught up by the steering of the mid-latitude westerlies... the dynamics (can draw some of the upper level strong winds down to the surface) when combined with the jet stream & embedded disturbances... combined with swift forward momentum (speeding east), it could all add up to a unique weather situation - severe weather - for many states & populated areas far from the initial intense landfall. There is a precedent for such - Ike in September, 2008 came ashore in Texas & brought damaging winds as far away as Cincinnati, Ohio.

On a sidenote: overall conditions across the Atlantic Basin appear to continue to be “ready to go” as we move into early Sept. (see velocity potential anomalies map below). I’m also tracking at least one potential long track tropical disturbance soon to move westward across the Atlantic that could be near some part of the U.S. between ~Sept. 3 & Sept. 9th as well as a wave/disturbance that could be over the Caribbean next week.

Fascinating microwave imagery courtesy CIMMS (Cooperative Institute for Meteorological Satellite Studies) shows the rapid intensification 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:

August hurricane landfalls since 1851 courtesy Dr. Phil Klotzbach:

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 couple of tropical waves over the far Eastern Atlantic are marching west with at least some potential for gradual development. Nothing to threaten the Caribbean through at least the weekend... nothing “new” to threaten the U.S. through at least the middle of next week.

There is also some “disturbed weather” - disorganized showers & t’storms - over parts of the Western Caribbean. Something to keep an eye on if the storms persist.