Tropical Storm Marco Discussion Number 9
NWS National Hurricane Center Miami FL AL142020
1000 AM CDT Sat Aug 22 2020
Reconnaissance data, geostationary and microwave satellite imagery,
and radar data from Cuba all indicate that Marco is strengthening
quickly this morning. The Air Force Reserve Hurricane Hunters
measured a peak 850-mb flight-level wind of 69 kt, and there were
several SFMR measurements of 50-55 kt to the northeast of the
center. These data support raising Marco's initial intensity to 55
kt, and the central pressure based on dropsonde data has fallen to
992 mb. The crew on the plane reported the formation of a partial
eyewall, which agrees with what we've seen on recent microwave and
radar images.
The track forecast has been complicated by the fact that the plane
has fixed Marco's center to the east of the previous forecast
track, and that makes the current motion north-northwestward, or
340/10 kt. The subtropical ridge currently located over the
southwestern Atlantic is forecast to build westward along the
northern Gulf Coast during the next few days, and this expanding
ridge is expected to push Marco northwestward and then eventually
westward while the cyclone moves across the Gulf of Mexico. This
general thinking has not changed, but the adjusted initial position
ended up shifting the track guidance to the north and east on this
cycle. In response, the new NHC track forecast has been adjusted
eastward and northward during the first 3 days and is generally
between the HCCA and TVCN consensus aids.
Marco has finally tapped into the favorable conditions over the
northwestern Caribbean Sea, and the cyclone's overall small size and
small radius of maximum winds makes it susceptible to quick changes
in intensity. The tropical storm is just beginning to move into a
higher zone of shear to its north, but conditions should remain
conducive enough for Marco to intensity to a hurricane during the
next 24 hours. After that time, southwesterly shear is expected to
increase over 20 kt by day 2 and then over 30 kt by day 3, and those
conditions, along with the cyclone's small size, should cause
weakening as Marco gets closer to the central and northwestern Gulf
coast. The updated NHC intensity forecast has been increased during
the first 2 days and lies above the HCCA/Florida State
Superensemble solutions but below the SHIPS/LGEM scenarios. The
intensity forecast comes back in line with the previous forecast by
day 3 during the expected weakening phase, and Marco is ultimately
expected to dissipate over Texas by the end of the forecast period.
The updated track forecast suggests that watches could be required
for a portion of the central Gulf Coast later today.
Key Messages:
1. Marco is forecast to strengthen to a hurricane as it moves into
the southeastern Gulf of Mexico by tonight, and tropical storm
conditions are expected over the northeastern coast of the Yucatan
Peninsula and in extreme western Cuba. Heavy rainfall is also
expected in the eastern portions of the Mexican states of Quintana
Roo and Yucatan, and across far western Cuba, which could result in
flash flooding.
2. Marco is expected to move across the central Gulf of Mexico as a
hurricane Sunday and approach the central Gulf Coast on Monday.
There is an increasing risk of impacts from storm surge, winds, and
heavy rainfall from the upper Texas coast to Louisiana early next
week, and interests there should monitor the progress of Marco, as
storm surge, tropical storm, and/or hurricane watches could be
issued later today.
FORECAST POSITIONS AND MAX WINDS
INIT 22/1500Z 20.9N 85.3W 55 KT 65 MPH
12H 23/0000Z 22.1N 86.0W 65 KT 75 MPH
24H 23/1200Z 23.9N 87.1W 75 KT 85 MPH
36H 24/0000Z 25.6N 88.4W 75 KT 85 MPH
48H 24/1200Z 27.2N 89.9W 70 KT 80 MPH
60H 25/0000Z 28.5N 91.6W 60 KT 70 MPH
72H 25/1200Z 29.1N 93.6W 50 KT 60 MPH
96H 26/1200Z 29.3N 96.6W 35 KT 40 MPH...INLAND
120H 27/1200Z...DISSIPATED
$$
Forecaster Berg
Tropical Storm Marco Advisory Number 9
NWS National Hurricane Center Miami FL AL142020
1000 AM CDT Sat Aug 22 2020
...MARCO STRENGTHENING QUICKLY...
...FORECAST TO BECOME A HURRICANE LATER TODAY...
SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...20.9N 85.3W
ABOUT 105 MI...170 KM ENE OF COZUMEL MEXICO
ABOUT 75 MI...120 KM SSW OF THE WESTERN TIP OF CUBA
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NNW OR 340 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...992 MB...29.30 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
The government of Cuba has issued a Tropical Storm Warning for the
province of Pinar del Rio.
The government of Mexico has discontinued the Hurricane Watch and
Tropical Storm Warning for the eastern Yucatan coast south of
Cancun.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for...
* Province of Pinar del Rio Cuba
* Cancun to Dzilam Mexico
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within
the next 12-24 hours.
Interests along the coasts of Louisiana and Texas should monitor
the progress of Marco. Watches will likely be required for a
portion of this area later today.
For storm information specific to your area, please monitor
products issued by your national meteorological service.
DISCUSSION AND OUTLOOK
----------------------
At 1000 AM CDT (1500 UTC), the center of Tropical Storm Marco was
located by an Air Force Reserve Hurricane Hunter aircraft near
latitude 20.9 North, longitude 85.3 West. Marco is moving toward
the north-northwest near 12 mph (19 km/h), and this general motion
is expected to continue through Sunday morning. A gradual turn
toward the northwest and west-northwest is expected to begin Sunday
afternoon and continue through Tuesday morning. On the forecast
track, Marco's center will move through the Yucatan Channel into
the southeastern Gulf of Mexico by this evening. Marco will then
move across the central Gulf of Mexico on Sunday and approach the
central and northwestern Gulf coast on Monday and Tuesday.
Data from the Hurricane Hunter aircraft indicate that maximum
sustained winds have increased to near 65 mph (100 km/h) with
higher gusts. Additional strengthening is forecast during the next
day or two, and Marco is expected to become a hurricane later
today. Weakening is forecast to occur on Monday and Tuesday.
Tropical-storm-force winds extend outward up to 45 miles (75 km)
from the center.
The estimated minimum central pressure is 992 mb (29.30 inches).
HAZARDS AFFECTING LAND
----------------------
WIND: Tropical storm conditions are expected within the warning
area in Cuba today. Tropical storm conditions are also still
possible today within the warning area along the northeastern coast
of the Yucatan Peninsula of Mexico.
RAINFALL: Marco is expected to produce 1 to 4 inches of rain, with
isolated maximum amounts of 6 inches possible, across the eastern
portions of the Mexican states of Quintana Roo and Yucatan, and
across far western Cuba. This rainfall may result in areas of flash
flooding.
NEXT ADVISORY
-------------
Next intermediate advisory at 100 PM CDT.
Next complete advisory at 400 PM CDT.
$$
Forecaster Berg |