Tropical Depression Eighteen has developed in the northwestern Caribbean, and it is expected to contribute to heavy rain in South Florida this weekend and provide an injection of moisture to an East Coast storm system early next week.

Data from an Air Force Reserve Reconnaissance aircraft found that this system had formed into a tropical depression Saturday morning.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_ww1_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_ww1_1280x720.jpg 400w, https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_ww1_1280x720.jpg 800w" > Current Tropical Storm Watches and Warnings At a Glance Tropical Depression Eighteen has formed in the northwestern Caribbean.

This system will bring heavy rain to parts of Cuba and the Cayman Islands Saturday.

Heavy rainfall and gusty winds may affect Florida this weekend.

This system will also provide an injection of moisture to an East Coast storm system Sunday into Monday.

Tropical storm warnings have been issued for the Cuban provinces of Isla de la Juventud, La Habana, Ciudad de la Habana, Matanzas, Cienfuegos, and Villa Clara and for the northwestern Bahamas. Tropical storm conditions are expected within these areas within the next on Saturday.

A tropical storm watch has been issued for portions of southeastern Florida, the Upper Florida Keys and the central Bahamas. The strongest winds are expected to remain to the east of its center, but a slight deviation in its track or an increase in the size of the wind field could bring tropical-storm force winds to the areas in the watch.

Conditions are conducive for additional development, and there is a chance that this tropical depression may become a tropical storm later this weekend. If this system becomes a tropical storm, it will attain the name "Philippe."

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_storm_info_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_storm_info_1280x720.jpg 400w, https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_storm_info_1280x720.jpg 800w" > Current Storm Status

Ocean temperatures continue to run 1 to 3 degrees above average, or in the mid-80s, across the majority of the Caribbean Sea, which is plenty supportive for tropical growth and development.

Land interaction and increasing wind shear, however, should hinder any quick intensification. Slow intensification is expected.

(MORE: Hurricane Central )

Tropical Depression Eighteen is expected to track northeastward and cross western and central Cuba on Saturday afternoon, and move through the northwestern Bahamas Sunday morning.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_swath_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_swath_1280x720.jpg 400w, https://s.w-x.co/staticmaps/MAX_WEB_TROP_ATL18_swath_1280x720.jpg 800w" > Projected Path and Intensity

Heavy Rain Possible in the Caribbean and Florida This Weekend

In the near-term, will bring the threat of heavy rain over the Cayman Islands and portions of Cuba Saturday. The downpours could eventually lead to flooding and mudslides.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/DCT_SPECIAL2_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/DCT_SPECIAL2_1280x720.jpg 400w, https://s.w-x.co/staticmaps/DCT_SPECIAL2_1280x720.jpg 800w" > Current Radar, Watches and Warnings

Four to eight inches of rainfall is likely in the Cayman Islands, western and central Cuba and the northern Bahamas, with isolated totals as high as 10 inches through Sunday.

<img class="styles__noscript__2rw2y" src="https://s.w-x.co/staticmaps/DCT_SPECIAL22_1280x720.jpg" srcset="https://s.w-x.co/staticmaps/DCT_SPECIAL22_1280x720.jpg 400w, https://s.w-x.co/staticmaps/DCT_SPECIAL22_1280x720.jpg 800w" > Rainfall Forecast Through Saturday

The main impact from this system in southern Florida at this time appears to be heavy rainfall Saturday into early Sunday. Some gusty winds are also possible, particularly in the coastal waters.

Up to four inches of rain is possible in southern Florida, with isolated totals up to six inches. Localized flash flooding is possible, especially in urban areas such as Miami and West Palm Beach.

This has prompted the National Weather Service to issued flood watches for much of southeastern Florida into early Sunday morning.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/1027-tropics4.png?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com/util/image/w/1027-tropics4.png?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com/util/image/w/1027-tropics4.png?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > Steering pattern that will bring this tropical system northward.

There is also the risk of a few tornadoes in far South Florida and the Florida Keys midday Saturday into the evening.

The moisture from Tropical Depression Eighteen will first get drawn north and then northeastward by a southward dip in the jet stream that will sweep through the central and eastern states late this week into the weekend.

Moisture Injection For Strong East Coast Storm

By Sunday, the area of enhanced moisture associated with Tropical Depression Eighteen will be in the western Atlantic Ocean, just off the southeast U.S. coastline.

This moisture will then get pulled into a storm system advancing through the eastern states, providing additional fuel for heavy rain in parts of the mid-Atlantic and Northeast regions Sunday into Monday. The heavy rain may cause some flooding problems in the Northeast region.

For more on this story, click the link below.

(MORE: Powerful Coastal Storm Could Bring Damaging Winds, Flooding Rainfall to the Northeast Starting This Weekend )

Western Caribbean a Hot Spot For Late-Season Development

You'll note in the chart below that there is a strong clustering of dots in the southwestern and northwestern Caribbean Sea. This is a hotbed of tropical origins that we'll be watching through the end of October and into November.

As the season begins to wind down, the warmest waters – 80 degrees and above – in the Atlantic Basin will recede to the Caribbean, Gulf of Mexico and far western Atlantic while wind shear and dry air generally increase across the basin.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com//util/image/w/nov_origins.png?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com//util/image/w/nov_origins.png?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com//util/image/w/nov_origins.png?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > November Tropical Origins Origins for November tropical storms and hurricanes.

November sees one more tropical storm or hurricane, on average, according to the National Hurricane Center. More than 7 percent of the season's activity is yet to come in terms of average Accumulated Cyclone Energy (ACE), a metric used to measure wind energy produced by tropical cyclones.

These cyclones typically move northeastward from the Caribbean or western Atlantic ahead of sweeping cold fronts from North America. These systems can threaten Florida, Cuba, the Bahamas and Bermuda, but can occasionally threaten areas closer to the U.S. East Coast, especially in October and early November.