UPDATE/7 p.m. Sunday
The Sunday evening forecast from the National Hurricane Center reported location changes and individual characteristics for newly formed tropical storms Emily and Franklin as well as Tropical Depression 6.
The NHC forecast other systems being watched, with TS Emily, TS Franklin and TD 6, were making moves to head out into the Atlantic. Meanwhile, a Gulf-bound system continued toward the west coast of the Gulf of Mexico.
For the North Atlantic, Caribbean Sea and the Gulf of Mexico, active systems:
TS EMILY: The large area of low pressure being monitored over the last several days to the west of the Cabo Verde Islands finally developed Sunday into a well-defined circulation per recently received satellite wind data. In addition, wind data also suggest the system has developed a robust wind field on its northern semicircle.
Advisories are being initiated on Tropical Storm Emily with maximum sustained winds of 45 knots.
The estimated motion of the tropical storm is slowly off to the west-northwest. Over the next several days, Emily should maintain a general west-northwestward motion as it remains steered by a low-level ridge centered to its north. A gradual turn to the north is anticipated after Emily becomes a remnant low.
The NHC said that Emily might already be near its peak intensity, as vertical wind shear is expected to substantially increase over the cyclone in the next 24-36 hours as it remains embedded in a fairly dry mid-level environment. While it is possible a bit more intensification occurs today, it seems more likely the system will soon succumb to the
increasingly hostile environment over the next several days.
Some models suggest Emily will cease to produce organized convection in about 48 hours, and the official intensity forecast shows it becoming a post-tropical remnant low at that time. There is some chance the environment becomes more favorable again in 4-5 days, but a regeneration scenario will not be shown in the official forecast for now.
The NHC also is issuing advisories on Tropical Depression Six, located several hundred miles east of the northern Leeward Islands and on newly formed Tropical Storm Emily, located about 1,000 miles west-northeast of the Cabo Verde Islands.
TS FRANKLIN: Sunday afternoon the NHC received a wealth of data from both a NOAA reconnaissance mission and satellite imagery near the area of low pressure located in the eastern Caribbean Sea. Earlier visible satellite imagery showed the system had likely formed a tight low-level vortex based on the earlier cloud motions before a convective burst obscured the center. Scatterometer data that clipped the system on the east side also showed winds near tropical storm intensity.
The NOAA aircraft flew through the system shortly thereafter, and found the system had indeed formed a well-defined center, with 950-mb flight level winds of 51 kt just to the northeast of the center. All this information confirms that Tropical Storm Franklin formed Sunday afternoon.
Over the next 24 hours this general motion should continue while the system remains steered by a narrow mid-level ridge. Thereafter, a large mid-ocean trough over the western Atlantic will produce a pronounced weakness in this ridging, likely causing the tropical storm to make a sharp turn northward, bringing the storm near or over the large island of Hispaniola in about 48-60 hours.
Afterwards, another mid-latitude trough is forecast to amplify southward, maintaining this weakness, and resulting in Franklin turning northeastward towards the end of the forecast period.
Intensity wise, Franklin may have to deal with a bit of westerly wind shear in the short-term, limiting more robust intensification early on. However, this shear drops off as the system makes its turn northward towards Hispaniola a bit more intensification is shown with a 55-kt intensity peak as Franklin approaches the coast. The intensity forecast then is complicated by the fact that Franklin will likely pass near or over the island sometime in the 2-3 day time period, and some weakening is shown during this time.
However, the forecast environment after the system re-emerges into the Western Atlantic looks mostly favorable, with reintensification likely as long as the system is not too disrupted by the higher terrain of Hispaniola. The NHC intensity forecast is in good agreement with the consensus aids, and lies closest to the HFIP corrected consensus approach through the forecast period.
Based on the current track forecast, a tropical storm watch has been issued for the entire southern coastline of Haiti and the Dominican Republic.
1. Western Gulf of Mexico (AL91):
Showers and thunderstorms have increased this evening, and are becoming better organized in association with a trough of low pressure located in the eastern Gulf of Mexico. Environmental conditions appear favorable for development of this system as it moves westward at about 15 to 20 mph across the central Gulf of Mexico. A tropical depression or storm is likely to form as it approaches the western Gulf of Mexico coastline by Tuesday.
Interests in the western Gulf of Mexico should monitor the progress of this system. Tropical storm watches or warnings may be necessary on Monday for portions of the southern Texas and northern Mexico coastlines.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 7 days...high...70 percent.
2. Eastern Tropical Atlantic:
A large area of disorganized showers and thunderstorms over the far eastern tropical Atlantic is associated with a tropical wave located near the Cabo Verde Islands. Environmental conditions appear conducive for gradual development of this system, and a tropical depression is likely to form later this week while it moves west-northwestward across the eastern tropical Atlantic.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 7 days...high...70 percent.
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