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Tropical Depression Seven-E Discussion Number 1

Wiki-Hurricanes Forecast Center

10:00 PM CDT Fri Jun 29 2018

The area of disturbed weather a few hundred miles south of Acapulco, Mexico, has become better defined today. An OSCAT pass from 1456z this morning showed that the low-level circulation was closed, albeit slightly elongated. However, high-resolution visible satellite imagery from before sunset indicated that this feature was continuing to become more circular. Convection is becoming more centrally focused, and there are several formative spiral bands to the north and south of the center. Thus, advisories are being initiated on the seventh tropical depression of the season, and the initial intensity is set to 25kt in accordance with an estimate of T1.5/25kt from TAFB.

Seven-E is being steered west by two mid-level ridges north of the cyclone, one stronger feature centered offshore Texas/Louisiana, and the second centered southwest of Baja California Sur. This motion is expected to continue for the next 36 to 48 hours as the storm consolidates. Thereafter, Seven-E is expected to move more west-northwest as it increases in strength and reaches the western periphery of the aforementioned ridging. That motion should continue for the rest of the period.

The intensity forecast is complicated. The upper-level environment is characterized by moderate westerly shear on the order of 15kt, originating from a weak trough along the coastline of southwestern Mexico. Latent heat release from the organizing cyclone should dissipate this feature over the next 24 hours, allowing anticyclonic flow aloft to expand and decrease shear below 10kt. Mid-level relative humidity values are above 70 percent and should remain in this ballpark for the next 5 days. Ocean temperatures, meanwhile, should remain beyond sufficient for intensification through 96 hours, at which time Seven-E will begin to approach a sharp temperature gradient. It should be noted that a moderate convectively-coupled kelvin wave passed over the system last night, and associated environmental conditions are most favorable three days thereafter. The culmination of these factors would support significant intensification of Seven-E over the next few days, perhaps rapid at times once an inner core is established. The only obvious limiting factor is the broad nature of Seven-E, which may prevent an even stronger storm than currently forecast. The current prediction is closest to the FV3, HWRF, and SHIPS models.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0300Z 25 KT 30 MPH

12H 30/1200Z 30 KT 35 MPH

24H 01/0000Z 35 KT 40 MPH

36H 01/1200Z 45 KT 50 MPH

48H 02/0000Z 55 KT 65 MPH

72H 03/0000Z 80 KT 90 MPH

96H 04/0000Z 105 KT 120 MPH

120H 05/0000Z 95 KT 110 MPH

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