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97L has now been declared Tropical Depression 14. 

Tropical Depression Fourteen Discussion Number 1 NWS National Hurricane Center Miami FL AL142020 1100 AM EDT Thu Aug 20 2020

Visible satellite images indicate that the area of disturbed weather moving across the central Caribbean Sea has developed a closed surface circulation, with the center embedded beneath cellular convective cells and a large cirrus canopy. Also, convection has increased in organization, and TAFB and SAB have given the system classification of T2.0/30 kt and T1.5/25 kt, respectively. Therefore, advisories are being initiated on Tropical Depression Fourteen with maximum winds of 30 kt. An expected ASCAT pass later today and an Air Force Reserve Hurricane Hunter mission scheduled for this afternoon should give us a better handle on both the depression's center location and its maximum winds. The depression continues to move westward at a pretty good clip, currently estimated to be on a heading of 280 degrees at 18 kt. This motion is being driven by the western extent of the Bermuda high, which currently noses into the northwestern Caribbean Sea. However, a deep-layer trough over the Gulf of Mexico is expected to become the main driver in the coming days, causing the cyclone to slow down and turn rather suddenly toward the west-northwest and northwest in the next 24-36 hours. A general northwestward motion should then continue until the end of the 5-day forecast period, bringing the system across the Yucatan Peninsula Saturday night and into the central and western Gulf of Mexico early next week. Most of the reliable track models are clustered close to one another, and the official NHC track forecast is therefore very close to the multi-model consensus aids, including the HCCA model.

Once the depression slows down during the next 24-36 hours, environmental conditions appear ideal for strengthening. The magnitude of vertical shear is expected to be less than 10 kt for at least the next 2 days, while the system will be moving over the deep, warm waters of the northwestern Caribbean Sea, where sea surface temperatures are 29-30 degrees Celsius. Given these conditions, some of the intensity guidance actually appears more muted than I would have expected, and I have therefore elected to closely follow the SHIPS and LGEM models, which are near the upper end of the guidance envelope. It is possible that the depression could be near or at hurricane strength when it approaches the Yucatan Peninsula of Mexico in 2-3 days. Some weakening is anticipated when the center moves over land, and then re-strengthening is likely after it moves over the Gulf of Mexico. There will be an increase in shear over the Gulf in 4-5 days, and right now there is greater-than-normal uncertainty in how this will affect the cyclone's intensity at that point. For now, the official forecast on days 4 and 5 shows a flat-lined intensity, and this scenario lies a little above the ICON intensity consensus and the HCCA model solution. Key Messages:

1. Tropical Depression Fourteen is expected to strengthen over the northwestern Caribbean Sea through Saturday, and it could produce tropical-storm-force winds and heavy rainfall over portions of the coast of Honduras and the Bay Islands beginning tonight through Friday. The system could be near or at hurricane strength when it reaches the Yucatan Peninsula of Mexico late Saturday, and watches could be required for a portion of that area later today.

2. The system is expected to move into the south-central Gulf of Mexico as a tropical storm on Sunday. Some strengthening is anticipated while it moves northwestward over the western Gulf of Mexico early next week, but it is too soon to know exactly how strong it will get or the location and magnitude of impacts it will produce along the central or northwestern Gulf Coast. Interests in that area should continue monitoring the progress of this system over the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT 20/1500Z 15.1N 79.7W 30 KT 35 MPH

12H 21/0000Z 15.5N 81.9W 35 KT 40 MPH

24H 21/1200Z 16.3N 84.2W 40 KT 45 MPH

36H 22/0000Z 17.1N 85.5W 50 KT 60 MPH

48H 22/1200Z 18.4N 86.4W 55 KT 65 MPH

60H 23/0000Z 19.9N 87.4W 60 KT 70 MPH

72H 23/1200Z 21.5N 88.9W 45 KT 50 MPH

96H 24/1200Z 25.0N 92.0W 50 KT 60 MPH

120H 25/1200Z 28.0N 94.0W 50 KT 60 MPH

$$ Forecaster Berg

Track is straight for the Yukatan at something close to hurricane intensity.

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Edited by Jo Farrow
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Posted (edited)

Center is now somewhere close to the coast of Honduras and forecast to become a Hurricane near the Yukatan (and again near Texas). 

Right now its worth saying it apparently has multiple surface centers slowing development. 

FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 15.4N 83.1W 30 KT 35 MPH

12H 21/1800Z 16.3N 84.3W 40 KT 45 MPH

24H 22/0600Z 17.7N 85.4W 50 KT 60 MPH

36H 22/1800Z 19.2N 86.4W 60 KT 70 MPH

48H 23/0600Z 20.7N 87.5W 50 KT 60 MPH...INLAND

60H 23/1800Z 22.5N 88.8W 50 KT 60 MPH...OVER WATER

72H 24/0600Z 24.5N 90.2W 65 KT 75 MPH

96H 25/0600Z 28.1N 93.0W 65 KT 75 MPH

120H 26/0600Z 30.4N 94.6W 45 KT 50 MPH...INLAND

Edited by summer blizzard
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The track has shifted to the north so he may miss the Yucatan. Despite that the NHC is not expecting him to make it to hurricane strength.

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3 minutes ago, karyo said:

The track has shifted to the north so he may miss the Yucatan. Despite that the NHC is not expecting him to make it to hurricane strength.

When I read one of the updates yesterday,  the NHC used the word " Mysteriously" . The depression was forecast to develop with favourable conditions but didn't. So even NHC was surprised. Maybe Marco will defy their forecast again.

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10 minutes ago, Had Worse said:

When I read one of the updates yesterday,  the NHC used the word " Mysteriously" . The depression was forecast to develop with favourable conditions but didn't. So even NHC was surprised. Maybe Marco will defy their forecast again.

Yes, tropical systems often surprise us .

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Just as I said this NHC has updated again and they now expect Marco to become a hurricane. They are still thinking that he will be downgraded to a tropical storm before the US landfall.

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It seems like it failed to develop as quickly as previously forecast because it had competing low level centers in a wider mid level envelope. Once a dominant center formed yesterday afternoon and started to sustain convection the storm wrapped its convection around a single point and intensified. 

Shear picks up overnight but is probably just about manageable until Tuesday when it will start to be ripped apart somewhat.  

SHIPS Prob RI for 25kt/ 24hr RI threshold= 66% is 6.0 times climatological mean (10.9%)

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Posted (edited)

GFS12z only has 1005mb to start (18z will have the recon data) but critically it actually has it 7mb deeper at landfall suggesting Marco may cope with the shear. 

Edited by summer blizzard
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Recon confirms that the eyewall is now closed and 10 miles wide (close to pinhole). 

Marco will be a Hurricane at the next advisory.

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Seems Marco probably became a hurricane but then dropped back, it has since adopted a more sheared appearance although forecast to reach hurricane strength today.

Hurricane Warnings have been issued for southern Louisiana.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0900Z 23.7N 87.0W 60 KT 70 MPH

12H 23/1800Z 25.3N 87.6W 65 KT 75 MPH

24H 24/0600Z 27.3N 88.6W 65 KT 75 MPH

36H 24/1800Z 29.0N 89.7W 65 KT 75 MPH

48H 25/0600Z 29.9N 91.5W 45 KT 50 MPH...INLAND

60H 25/1800Z 30.5N 93.1W 30 KT 35 MPH...INLAND

72H 26/0600Z 31.0N 95.0W 25 KT 30 MPH...INLAND

96H 27/0600Z...DISSIPATED

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We have confirmation.

...MARCO BECOMES A HURRICANE... ...LIFE-THREATENING STORM SURGE AND HURRICANE-FORCE WINDS EXPECTED ALONG PORTIONS OF THE U.S. GULF COAST...

Data from an Air Force Reserve Hurricane Hunter aircraft indicate that Marco has strengthened into a hurricane with maximum winds of 75 mph (120 km/h) with higher gusts.

 

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NHC performance has been pretty poor here.

-

Marco looks like making landfall as a TS in Florida state ( or the coastal bit of mississippi ) 

Laura looks like tracking west of Cuba & heading towards texas. Ironically Louisiana will be spared both...

Edited by Steve Murr
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33 minutes ago, Steve Murr said:

NHC performance has been pretty poor here.

-

Marco looks like making landfall as a TS in Florida state ( or the coastal bit of mississippi ) 

Laura looks like tracking west of Cuba & heading towards texas. Ironically Louisiana will be spared both...

Mid-level Center is being ripped apart by the south westerly shear and taken north east, the low level center will theoretically still make the turn (steering currents are actually more conducive to a turn if weaker). Of course what that really means is that we'll probably see a naked swirl and a bit of wind somewhere around Louisiana devoid of any convection.

Score one for yesterdays Euro i guess. 

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Maybe - depends on timing of recon but hurricane winds were found on the data.

The shear vectors this morning show the strong SW shear impacting Marco & the moderate Northerly shear over Laura.

With time for laura this moderates into a more favourable postition. This combined with a track over water with high OHC should signifiy decent regeneration towards a hurricane.

638E9F85-8438-4514-AFF8-753CE1D328AE.thumb.jpeg.7d2052e9e71a9a77db19a74cf19f5eec.jpeg

Edited by Steve Murr
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11 hours ago, summer blizzard said:

Mid-level Center is being ripped apart by the south westerly shear and taken north east, the low level center will theoretically still make the turn (steering currents are actually more conducive to a turn if weaker). Of course what that really means is that we'll probably see a naked swirl and a bit of wind somewhere around Louisiana devoid of any convection.

Score one for yesterdays Euro i guess. 

Theres your naked swirl just off the coast of LA

- Stupid really the track of the low has turned out of actually from a cone POV but all the 'weather' has hit the florida coast

8EBF440A-350C-413D-9E85-5D778155CF81.thumb.jpeg.b25a6a93a770c7da003fbe76df5b724e.jpeg

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Reading the NHC discussions, it seems Marco became a depression before Laura reached the Gulf. Therefore didn't even manage two TS in the Gulf at the same time, nevermind two hurricanes as was being hyped by the press at the weekend.

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