Satellite image of Laura - Marco
Visible GOES-16 satellite image of Tropical Storm Marco (top) and Tropical Storm Laura (bottom) at 10:40 a.m. EDT Monday, August 24. (Image credit: NOAA/RAMMB)

Tropical Storm Laura brought torrential rains on Sunday and Monday to the nations of the Dominican Republic and Haiti, which share the island of Hispaniola. The highest 24-hour rainfall amount in the Dominican Republic was 11.70 inches in Barahona, on the southwest coast.

According to weather.com, at least four deaths occurred in the Dominican Republic, where one million customers lost power. In Haiti, a personal weather station in the capital of Port-au-Prince recorded 6.61 inches of rain. Floods in Haiti killed at least nine people, and another two were missing. Laura mostly spared Puerto Rico severe impacts, with 2 – 4 inches of rain falling across the southern portion of the island, but it did knock out power to approximately 100,000 customers in Puerto Rico.

Figure 1
Figure 1. Observed rainfall in the Dominican Republic for the 24-hour period ending 8 a.m. EDT Sunday, August 23, 2020. Rainfall in excess of four inches (101.6 mm, red colors) affected much of the southern portion of the nation. The highest rainfall amount was 11.70 inches in Barahona, in the southwest Dominican Republic. (Image credit: ONAMET)

Laura made landfall in eastern Cuba on Sunday night. At 7:51 p.m. EDT Sunday, Guantanamo Bay, Cuba recorded sustained winds of 60 mph, gusting to 72 mph. The base recorded 3.01 inches of rain from Laura through 8 a.m. EDT Monday.

On Monday morning, Laura moved off Cuba and emerged into the waters just south of the island. At 2 p.m. EDT Monday, Laura was located over the waters south of west-central Cuba, about 60 miles from the island. These waters were a very warm 30.5 degrees Celsius (87°F). Laura was headed west-northwest at 21 mph with top sustained winds of 60 mph and a central pressure of 1001 mb.

Radar from the Cayman Islands and Cuba showed that Laura did not have an inner core, and the storm’s spiral bands were not well-organized. However, satellite images late Monday morning showed a steady increase in heavy thunderstorms near Laura’s center, and the storm may be able to build a strong inner core by Monday evening.

Satellite images showed Laura had significantly expanded in size to the south of Cuba and was bringing heavy rains to Cuba, Jamaica, and the Cayman Islands. As of 2 p.m. EDT Monday, a personal weather station in Negril, Jamaica, had recorded 4.97 inches of rain. Wind gusts between 35 and 40 mph were recorded at both Kingston and Montego Bay on Monday morning. Wind gusts between 30 – 45 mph were common in central Cuba on Monday morning.

Figure 2
Figure 2. Radar image of Tropical Storm Laura at 10:30 a.m. EDT Monday, August 24. The storm was not well-organized, but it was bringing heavy rains to Cuba, Jamaica, and the Cayman Islands. (Image credit: Cayman Islands National Weather Service)

Laura was a very lopsided storm, with almost all of the heavy thunderstorm activity to the south of Cuba. High-level cirrus clouds were streaming out to the south, indicating good upper-level outflow on that side, but it was more restricted to the north than it had been on Sunday. Laura was embedded in a moderately dry region of the atmosphere, with a mid-level relative humidity of 60%; moderate upper-level wind shear of 10 – 15 knots was affecting the storm, driving dry air into the core and slowing development.

A track just south of Cuba, then into Gulf

Over the next four days, the Bermuda high, which is steering Laura, will be strong and will extend far to the west, forcing the storm generally to the west-northwest. The Monday morning runs of the models indicated that Laura will track just south of Cuba on Monday, with the storm crossing western Cuba and emerging into the Gulf of Mexico early Tuesday morning. If Laura is able to keep its center over water on Monday, it likely will maintain at least its current intensity, and probably strengthen by 5 – 10 mph before emerging into the Gulf of Mexico.

Figure 3
Figure 3. The 0Z Monday, August 24, forecast of the UKMET model, which has made the best track forecasts for Laura thus far. The model predicted a landfall in Texas to the southwest of Houston. Note that the 12Z Monday run of this model, had a landfall location near the Texas/Louisiana border, more in line with the official NHC forecast. (Image credit: weathermodels.com)

Intensification into strong hurricane likely in Gulf of Mexico

When Laura emerges into the Gulf of Mexico, conditions for intensification are expected to be very favorable. Ocean temperatures are a very warm 30 – 31 degrees Celsius (86 – 88°F) across much of the Gulf of Mexico, and an upper-level high-pressure system with light winds will bring light to moderate wind shear and excellent upper-level outflow. The atmosphere will be somewhat dry, with a mid-level relative humidity of 60%, but with that light wind shear, the dry air is unlikely to significantly impede intensification.

Tropical Storm Marco (see below) will be too small and too far away to bring increased wind shear from its upper-level outflow.

It will take a day or so for Laura to recover after its long struggle with Cuba, but immediately after leaving Cuba behind, the storm is over the warm, deep waters of the Loop Current, with its tremendous amount of ocean heat content (see yesterday’s post), leading Laura to steadily organize. This process may be slowed when Laura encounters a cool eddy in the Gulf on Tuesday afternoon, though, and in addition Laura will have to build up the entire northern portion of its circulation. Laura will expand in size on Tuesday and Wednesday, and will likely grow into a larger-than-average storm capable of generating a very large storm surge.

From Tuesday evening though landfall on Wednesday night, Laura will be passing over Gulf waters with very high heat content, and the top dynamical intensity models – the HWRF, HMON, and COAMPS – continued to predict in their 0Z and 6Z Monday runs that Laura would be at least a category 2 storm, and perhaps at category 4 strength by Wednesday evening, as it approaches landfall in Texas or western Louisiana. The 12Z Monday run of the SHIPS model gave a 24% chance that Laura would rapidly intensify by 65 mph by Wednesday morning, becoming a borderline category 3/category 4 hurricane. The official NHC forecast at 11 a.m. EDT Monday, however, called for a strong category 2 hurricane before landfall.

Figure 4
Figure 4. Model performance for Tropical Storm Laura for all of the forecasts made ending at 5 a.m. EDT (9Z) Monday, August 24. The UKMET model has been by far the best model, outperforming even the official NHC forecast at all times except for 12-hour forecast. (Image plotted using data from Brian Tang/SUNY Albany)

Where will Laura go?

The model solutions for Laura still have a wide spread, with much of Texas and Louisiana at risk for a potential landfall.

The model trend in recent days has been to build the Bermuda high steering Laura farther to west, pushing the storm more westward, towards Texas. This trend seems to have stabilized a bit, with the models agreeing on a landfall location between the central Texas coast and the central Louisiana coast.

The best-performing model for Laura so far has been the UKMET model, which has out-performed all other models and the official NHC forecast, except for those at 12-hour forecasts. The UKMET model’s 0Z Monday forecast predicted a landfall southwest of Houston, Texas, around 8 p.m. EDT Wednesday as an intensifying hurricane. This model was an outlier among the 0Z Monday guidance, though, and its landfall position lay outside of the NHC cone of uncertainty at 11 a.m. EDT Monday. Update: the 12Z  Monday run of UKMET model had a landfall location near the Texas/Louisiana border, more in line with the official NHC forecast.

The European model ensemble from 06Z Monday also leaned westward of the NHC cone (see below). Note that for about one-third of forecast cones, the actual track will extend outside the cone at some point. The cone is assigned a standard width each year, based on typical errors over the previous five years of tropical cyclones tracks. Some systems end up being less predictable – and some more predictable – than the cone implies. One wildcard in Laura’s future track may be the position of Tropical Storm Marco’s remnants, which may create a weakness in the ridge of high pressure steering Laura, and turn the storm more to the north over the northwest Gulf of Mexico.

Figure 5
Figure 5. Predicted path of Laura from the 6Z Monday, August 24 run of the European model’s 51 ensemble members (colored lines, which show minimum central pressure). The model’s operational-version track is shown as the black line. Model members showed a wide range of potential landfall locations along the coasts of Texas and Louisiana. (Image credit: weathermodels.com)

Steering currents will keep Laura moving steadily after it comes ashore, so it is unlikely to stall out and produce the type of catastrophic inland rains generated by Hurricane Harvey in 2017. Instead, storm surge and wind are most likely to be the greatest threats posed by Laura.

Residents along the Texas and Louisiana coasts should anticipate the possibility that Laura will rapidly intensify right up until landfall, potentially reaching major hurricane status.

Figure 6
Figure 6. Radar image of Tropical Storm Marco at 12:11 p.m. EDT Monday, August 24. (Image credit: Mark Nissenbaum/Florida State University)

Marco weakens dramatically off Louisiana coast

Tropical Storm Marco, which was briefly a Category 1 hurricane on Sunday in the southern Gulf of Mexico, no longer poses a serious threat to the U.S. coast after being ripped apart by strong wind shear on Monday.

Marco’s small size made it especially vulnerable to the destructive effects of shear and dry air. On Monday, the intense showers and thunderstorms (convection) associated with Marco were being pushed into the Florida Panhandle. Marco’s center of circulation continued to head toward the Louisiana coast, but with virtually no showers and thunderstorms around it. Bereft of the convection needed to support it, Marco’s circulation should weaken rapidly, with a downgrade to tropical depression possible as soon as Monday afternoon or evening.

As of 2 p.m. EDT Monday, Marco was centered about 40 miles southeast of the mouth of the Mississippi River. Top sustained winds were 40 mph, mainly in the convection well east of the storm, near the Florida Panhandle coast. Around Marco’s center, sustained winds were no more than 35 mph, according to surface microwave radiometer data from hurricane-hunter flights. Winds were generally 10 to 20 mph across southeast Louisiana, with gusts to 24 mph at Port Fourchon.

Marco’s weakening center is expected to arc west-northwestward near the Louisiana coast, and it is possible that Marco will not make landfall in the U.S. as a tropical storm, and instead be a tropical depression at landfall. Localized rainfall totals could end up exceeding 5″ in and near the Florida Panhandle, as Marco’s convection is channeled onshore away from the storm center. Lesser rainfall totals could push across far southern Alabama and Mississippi into southeast Louisiana by late Monday. Marco is no longer expected to generate a significant storm surge.

Figure 7
Figure 7. Two simultaneous storms in the Gulf of Mexico, as seen on the weather map at 8 am EDT September 4, 1933. The Great Cuba-Brownsville Hurricane of 1933, a category 3 storm with 125 mph winds, was approaching landfall in Brownsville, Texas (left) and the Treasure Coast Hurricane of 1933, with 75 mph winds (right), was over central Florida, after making landfall near West Palm Beach as a category 3. Twelve hours after this map was drawn, both storms were briefly in the Gulf of Mexico at the same time. They were 900 miles apart, which is right at the limit at where the Fujiwara effect occurs. The NOAA historical hurricane site shows that there was no Fujiwara interaction between the two storms. (Image credit: NOAA library)

Two U.S. landfalls in a three-day period: a rare occurrence

Assuming that Marco actually ends up making an official landfall, the expected landfall of Laura on Wednesday along the northwest Gulf Coast would give the U.S. two landfalls within a three-day period, a rare occurrence.

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According statistics provided by Dr. Phil Klotzbach of Colorado State University, the U.S. has experienced double landfalls within three days of each other on only 12 other occasions since 1851 – an average of once every 14 years. The most recent double landfall occurred in 2004, when two pairs of double landfalls occurred. Tropical Storm Gaston hit South Carolina at 12Z Aug. 29, and Tropical Storm Hermine hit Massachusetts just 39 hours later. Earlier that same year, Hurricane Charley had hit southwest Florida just 30 hours after Tropical Storm Bonnie had made landfall in the Florida Panhandle.

The shortest time on record between two continental U.S. landfalling hurricanes is the 23 hours that separated Treasure Hurricane (9/4/1933 at 5 UTC) and Cuba-Brownsville Hurricane (9/5/1933 at 4 UTC).

Perhaps the craziest U.S. tropical cyclone onslaught occurred in 1923, when three tropical storms hit the U.S. within a four-day period, between October 16 and October 19.

Editor’s note: Posted August 24, 2020, at 2:02 p.m. EDT. This post was updated at 2:15 p.m. EDT to reflect the latest NHC advisories and the 12Z run of the UKMET model.

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Topics: Weather Extremes
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Barfolomew
Barfolomew
2 months ago

Still lopsided and a good deal of dry air nearby, but it looks like deeper convection is starting to fill in some of the larger gaps near the center of circulation. Also, maybe a nascent feeder band setting up well to the west/southwest.
comment image

Barefootontherocks
Barefootontherocks
2 months ago

GFS trend gif four runs ending with Aug 25 12z
Click for big

gfs_mslp_pcpn_frzn_scus_fh42_trend.gif
jason weed
2 months ago

Hurricane Laura 2:00 PM

Hurricane Laura  2 PM  Tue Aug 25.png
jason weed
2 months ago

Hurricane Laura 2:00 PM Tue Aug 25 Hurricane Laura looking better by the hour

Michael Faria
Michael Faria
2 months ago

Good luck to everyone in Laura’s path, please evacuate while you all have the time.

Barefootontherocks
Barefootontherocks
2 months ago

12z GFS 42hrs

20200825 laura ridge .png
Barefootontherocks
Barefootontherocks
2 months ago

12z GFS at 42 hrs Click to enlarge

12z gfs 42 hr.png
Last edited 2 months ago by Barefootontherocks
Wyatt Washburn
Wyatt Washburn
2 months ago

Laura drink some dry air
Overperform don’t you dare
It’s 2020 cut us a break
Give us a storm surge everyone safely takes
Unexpected weakening would be nice to hear
Worry and fear avails us not
Make sure you’re ready that’s all I’ve got

VortexStar
VortexStar
2 months ago

Why is recon data on Levi’s site not updating? Anyone know if it’s a technical issue onboard the aircraft or what?

Barefootontherocks
Barefootontherocks
2 months ago

GALVESTON, Texas (KTRK) — 11:30 A.M. UPDATE: Galveston County Judge Mark Henry has issued a mandatory evacuation of the Bolivar Peninsula, as well as announcing suspension of ferry services from the area to Galveston Island.

According to Henry, the suspension is based on wave patterns and high winds expected from Hurricane Laura, which prompted the National Weather Service to issue Hurricane and Storm Surge warnings from San Luis Pass eastward along the upper Texas coast.

Henry also added Clear Lake Shores, Jamaica Beach, La Marque and Tiki Island to the mandatory evacuation order.

A new voluntary evacuation order was issued for Bayou Vista, Hitchcock and Kemah.

Hesitate to leave a link as that may be what’s triggering the “await moderation” message.

Last edited 2 months ago by Barefootontherocks
Barfolomew
Barfolomew
2 months ago

Interesting they suspend ferry service and the closer access to an interstate that it provides. I assume they don’t want to funnel evacuees into Galveston or Houston in case evacuations are ordered for those areas.

Barefootontherocks
Barefootontherocks
2 months ago
Reply to  Barfolomew

Possible. Might be the ferry itself and its route will soon become unsafe to travel.

Coastie1
Coastie1
2 months ago

I was first responder in Hurricane Ike and spent a couple months working Bolivar Peninsula. Really nice place but all along Crystal Beach area almost every house had been washed away. Visited there last year and it had make a nice recovery. Hope it doesn’t get too damaged this time.

Barfolomew
Barfolomew
2 months ago
Reply to  Coastie1

Thanks for your efforts as a first responder. That is a tough job.

Barefootontherocks
Barefootontherocks
2 months ago
Reply to  Coastie1

Wow. TY for the work you do. Glad to hear of the nice recovery! I share your hope for Bolivar. 🙂 I visited there two years before Ike. Rode the ferry into Galveston. Broke my heart to see the pictures of Ike’s aftermath.

Barfolomew
Barfolomew
2 months ago

Not quite what it was yesterday, but still a lot of dry air around Laura. Looks like a tongue of “very” dry air to the northeast is being pulled directly into the storm.
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Barefootontherocks
Barefootontherocks
2 months ago
Reply to  Barfolomew

Yeah, mid and lower levels look dry. Upper level, not so much, at least last time I checked which was a couple hours ago.

Karen
Karen
2 months ago

Can someone explain to me why the NHC has been keeping Laura headed to the TX/LA border while the GFS and ECMWF ensembles are centred on the Houston/Galveston area and barely even touch the border?

Barfolomew
Barfolomew
2 months ago
Reply to  Karen

Forecaster discretion? You’ve no doubt read it before, so skip it if it sounds familiar: don’t get too hung up on the exact center line of the path at this point.

Karen
Karen
2 months ago
Reply to  Barfolomew

Not talking about centre lines, of course. The whole cone is strangely shifted relative to the GFS and ECMWF ensembles. It’s like they’re taking the UKMET and HRWF and ignoring everything else. But while UKMET has sometimes been right (like a stopped clock), historically it’s not the best track forecaster, and certainly not worth discounting other models. And I can’t see why one would favour HRWF over, say, ECMWF ensembles… At the least you’d think they’d aim the cone between these two sets of possibilities.

Barfolomew
Barfolomew
2 months ago
Reply to  Karen

True. Every now and then the NHC forecaster includes why one model is favored over others which I always appreciate. In fact, yesterday they mentioned that they were reluctant to indicate a big shift in track (to the west) because the difference between model runs was so dramatic.

Karen
Karen
2 months ago
Reply to  Barfolomew

I guess time will tell. Something has to give, one way or another…

Barfolomew
Barfolomew
2 months ago
Reply to  Karen

True!

Karen
Karen
2 months ago
Reply to  Barfolomew

GFS ensemble seems to have drifted a bit further east with the 12z, at least… maybe halfway between Houston and the Beaumont, maybe closer to Beaumont. It’ll be really interesting to see the 12z ECMWF later today. If it shifts… good on the NHC 🙂

Barfolomew
Barfolomew
2 months ago
Reply to  Karen

Maybe worth noting via the wayback machine, that Ike made landfall around Galveston while Rita made landfall very close to Sabine Pass. While the wind damage to Port Arthur and Beaumont was severe with Rita, Ike’s overall impact was equal or worse for Port Arthur.

jeffs713
jeffs713
2 months ago
Reply to  Karen

The forecasters mention it in their forecast discussions. Basically, the models are swinging back and forth a bit, and major changes to the cone at this juncture would actually harm preparations and response. Also, they are following more closely what has worked well this season so far, and for Laura and Marco to date.

There is also likely a bit of concern regarding a repeat of Rita (read: panic) if they plot the cone directly over Houston.

Based on everything I’ve been watching/reading, my guess would be a landfall between High Island and Port Arthur (and I live on the north side of Houston, for reference).

Barfolomew
Barfolomew
2 months ago
Reply to  jeffs713

Depending on strength, that would be close to worst case scenario for Port Author/Beaumont, right? Specifically as far as storm surge goes.

Barfolomew
Barfolomew
2 months ago

Good day all. Laura is still looking surprisingly ragged so far today.

Terry
Terry
2 months ago

Is that an eye trying to form?

ww.png
Tweek
Tweek
2 months ago
Reply to  Terry

Hi Terry, I don’t think so.

Terry
Terry
2 months ago
Reply to  Tweek

yes it was an eye, time stamped!

Barfolomew
Barfolomew
2 months ago
Reply to  Terry

…or ingesting more dry air?

jeffs713
jeffs713
2 months ago
Reply to  Terry

Or just hasn’t built storms to cover the inner core in that quad. That feature is south of the COC.

Cthulhu Ferrigno
Cthulhu Ferrigno
2 months ago

You fail to mention that he said these are probably just minor speedbumps in the big picture of things. The shear is only very moderate, and also the surrounding air is not that dry. The “cooler” water is largely irrelevant because Laura is crossing it relatively quickly from a perpendiclar direction (won’t be over it long enough to upwell enough cool water)

Jexpat
2 months ago

GOES-East – Sector view: Gulf of Mexico
7 hour loop – 84 images – 5 minute update
(Click for loop)

Goes.gif