1. Marco is forecast to strengthen over the northwestern CaribbeanSea through Saturday as it approaches the northeast coast of theYucatan Peninsula. A Hurricane Watch and a Tropical Storm Warningare in effect for portions of that region.

2. The system is expected to move into the south-central Gulf ofMexico as a tropical storm on Sunday. Although some strengtheningis anticipated on Sunday, weakening is forecast as the systemapproaches the northwestern Gulf coast on Tuesday. It is still toosoon to know exactly the location and magnitude of impacts thesystem will produce along the central or northwestern Gulf Coast,and interests in that area should continue monitoring the progressof this system over the next few days.

CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Watch is in effect for...
- Punta Herrero to Cancun Mexico

A Tropical Storm Warning is in effect for...
- Punta Herrero to Dzilam Mexico

A Hurricane Watch means that hurricane conditions are possible within the watch area, in this case within 24 hours.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within 24 hours.

For storm information specific to your area, please monitor products issued by your national meteorological service.

WIND: Tropical storm conditions are expected to first reach the eastern Yucatan coast within the warning area this afternoon and will spread northward and westward within the warning area tonight, making outside preparations difficult or dangerous. Hurricane conditions are also possible within the hurricane watch area by this evening.

RAINFALL: Marco is expected to produce the following rainfall accumulations through Sunday: Eastern portions of the Mexican states of Quintana Roo and Yucatan: 3 to 6 inches, isolated maximum totals of 10 inches. Far western Cuba: 1 to 3 inches. This rainfall may result in areas of flash flooding.

At 400 AM CDT (0900 UTC), the center of Tropical Storm Marco was located near latitude 19.6 North, longitude 85.4 West. Marco is moving toward the northnorthwest near 12 mph (19 km/h). A northwestward motion is expected on Sunday, followed by a turn toward the northwest and westnorthwest early next week. On the forecast track, the center of Marco will approach the east coast of the Yucatan Peninsula of Mexico today. The center will approach the northeastern part of the Yucatan Peninsula by early evening and move over the central Gulf of Mexico toward the northwestern Gulf on Sunday and Monday followed by a track toward the northwestern Gulf coast Tuesday. Maximum sustained winds are near 45 mph (75 km/h) with higher gusts. Additional strengthening is forecast during the next couple of days as the system approaches the Yucatan peninsula and Marco could be near hurricane strength when it moves over the central Gulf of Mexico Sunday night and early Monday. Tropicalstormforce winds extend outward up to 70 miles (110 km) from the center.

The estimated minimum central pressure is 1005 mb (29.68 inches).

SFMR data from the last leg of the 53rd Air Force Reservereconnaissance aircraft indicated a couple of 48-50 kt winds, butwere associated with a significant spike in the rainfall rate.Additionally, the flight-level winds were only 36 kt in that area and the central pressure has increased a little to 1005 mb. The cloud pattern has improved during the past several hours with deep convection developing near the center and spiral bands forming over the eastern portion of cyclone. Based on a blend the hurricane hunter data and current subjective satellite intensity estimates, the initial intensity is raised to 40 kt.

Although the UW-CIMSS shear product and global models indicate afavorable upper wind pattern, GOES-16 sounder analysis data show ahigher than normal vertically stable environment in the westernCaribbean. This negative contribution maybe what's hamperingsignificant development. Consequently, as shown in the previousadvisory, only modest strengthening is indicated in the NHCforecast through 48 hours. Only the Decay SHIPS and LGEM intensity models indicate that Marco will become a hurricane in a couple of days. Both the HMON and HWRF have backed off of showing a hurricane in the Gulf. Afterward, increasing west-southwesterly shear should lead to weakening as the cyclone turns toward the northwestern Gulf coast. The NHC forecast lies between the higher LGEM/Decay SHIPS solution and the lower NOAA HCCA intensity model which indicates a peak intensity of 55 kt.

The initial motion is estimated to be west-northwestward, or 335/10kt. Marco is being steered toward the northwest by a mid- toupper-level cut-off low and associated trough extending into thesouthwestern Gulf from the Mississippi Valley. By Sunday, theaforementioned feature is forecast to lift northeastward allowingthe subtropical ridge to build back over the central gulf. Thisshould cause Marco to turn northwestward and west-northwestward early next week toward the the northwestern Gulf coast. Large-scale guidance generally agree that any binary direct or indirect interaction, while both systems are in the gulf and at near equal latitude, is unlikely at this point. The official track forecast has been adjusted to the right of the previous advisory and lies just to the left of the various multi-model consensus aids.The 34 kt wind radii have been adjusted based on the aircraftreconnaissance data and a 0224 UTC scatterometer pass.