Tropical Storm Erika shows some signs of weakening on path toward Florida

MIAMI, Aug. 26 (UPI) -- Tropical Storm Erika maintained strength Wednesday but showed some signs it is running into trouble as it churns westward with an expected landfall in Florida on Monday.

Erika had a modest area of thunderstorm activity on its east side and dry air was pushing into the storm's northwest side, exposing its center and disrupting circulation that allows the storm to build strength.

Dr. Rick Masters with Weather Underground sounds a pessimistic note on Erika's future Wednesday afternoon, giving it a 40 percent chance of dissipating by Saturday and a 30 percent chance it could reach the U.S. coast but as a disorganized collection of thunderstorms. He gives it just a 20 percent chance of making landfall in the U.S. as a hurricane.

A Hurricane Hunter aircraft visited the storm Wednesday afternoon and found a rainbow southeast of Erika's center.

National Hurricane Center forecasters continue to track Tropical Storm Erika straight to heavily populated South Florida on Monday, where at last report it was predicted to be a weak hurricane.

NHC forecasters remain unsure how strong Erika will become in the short-term, with computer models suggesting the storm either will quickly strengthen or come apart in the next two to three days. Forecasters are taking a middle ground, predicting Erika will slowly strengthen in the next three days and then grow more rapidly in days 4-5 over the Bahamas, reaching hurricane strength with 75 mph winds over the Fort Lauderdale and Miami, Fla., areas at 8 a.m. Monday.

Sustained winds Wednesday afternoon maintained an estimated 45 mph, though the NHC said this estimate could be "generous."

Tropical storm warnings are in effect for Puerto Rico, the Virgin Islands, and several other islands in the northeastern Caribbean. It's forecast to cross the Lesser Antilles Thursday morning, Puerto Rico Thursday night, Hispaniola on Friday and the Bahamas on Saturday.

A barrier of strong wind shear in its path and mountains in Puerto Rico and Hispaniola could cause Erika to weaken significantly in the next 72 hours, but if Erika makes it to the Bahamas as a well organized tropical storm late Friday, it could intensify rapidly and create major problems for the Bahamas and the U.S. East Coast, Masters said.

Computer models are now curving Erika to the northwest late in the forecast, with it skirting Florida's Atlantic coast positioned just a couple miles northeast of West Palm Beach at 2 p.m. on Monday as a weak hurricane. Nearly 6 million people live in South Florida's narrow, low-lying strip of developed land between the Everglades and Atlantic Ocean.

NHC forecasters cautioned that their forecast track errors over the past five years are 180 miles at day 4 and 240 miles at day 5. For Erika, that means on Monday it could be anywhere from moving into the Gulf near the Keys to moving into the open Atlantic off Florida's east coast. The current track takes the middle path, pointing it squarely at South Florida.

The next update on Erika will come late Wednesday night, Eastern time.