Forecasters are warning that a new tropical storm near Cuba this morning will merge with low pressure forming off the southeastern U.S. overnight to bring Central Maryland 2 to 4 inches of rain tonight and Thursday, with up to 6 inches in some locations.
Although the storm is forecast to bring sustained winds of 20 mph, gusting to 45 or 50 along the Western Shore of the Chesapeake, this is expected to be mainly a heavy rain event.
The National Weather Service has issued a Flash Flood Watch for Maryland from drought-stricken Washington County east to the Lower Eastern Shore - also reeling from a very dry summer. Light rain is expected to begin near the Chesapeake by early evening, increasing in intensity and moving westward overnight.
"Rainfall totals of two to four inches are expected, with isolated amounts up to five inches possible. This may cause streams and creeks to quickly rise out of their banks," the Watch says. "People living in areas that are prone to flash flooding should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. Motorists tonight and Thursday should be aware of the possibility of flooded roads. These should never be crossed."
A Coastal Flood Watch is also in effect for Thursday on the Maryland portion of the Chesapeake Bay as the approaching low and onshore winds conspire to drive water into the Western Shore's rivers and creeks. Tides are forecast to rise two to three feet above normal at high tides Thursday.
Urban flooding is expected, so Baltimore's Department of Public Works Wednesday asked residents to clear trash from storm drains in advance of the rain, and to secure trash that might wash into the storm sewers and clog them. To report storm drains that can't be easily cleared, officials asked residents to dial 311.
Maryland's Emergency Management Agency urged residents to assemble an emergency supply kit with water, non-perishable food, a flashlight and batteries, and and a battery-operated radio for monitoring weather conditions.
"Those living in in areas subject to flooding should be prepared to evacuate if needed," the agency said. "Motorists are reminded to never drive through standing water because several inches of fast-moving water can carry a vehicle down stream."
BGE officials said its crews were preparing for the heavy rain and strong winds, which could cause power outages. "At this time, given the projected path of the storm, we fully anticipate several thousand service interruptions," said A. Christopher Burton, senior vice president for gas and electric operations. "We strongly urge our customers to take the time now to prepare."
This latest round of extreme weather seems to have impressed even seasoned meteorologists. A forecaster at the NWS's Baltimore-Washington Forecast Office was moved to add this to his Wednesday morning forecast discussion:
"I'll say this - The weather of 2010 is something I won't soon forget. Blizzards, severe storms, record-breaking heat, drought, and now potential flooding."
There are several things playing into the very wet weather ahead for Central Maryland. The first is a trough of low pressure - a cold front - which is lurking just to our west. The second is the Bermuda High still lingering off the coast. Together, they have formed a kind of one-way wind corridor from the tropics to Maryland.
What's preparing to move up that corridor is a huge gusher of tropical moisture that has been percolating for a week in the northwestern Caribbean. That system is the newly-named Tropical Storm Nicole.
The National Hurricane Center says Nicole finally made tropical storm status this morning. It is a minimal storm, with top sustained winds of just 40 mph. But it's a very wet one that has been drenching Cuba, and is moving today to do the same to southern Florida. And then forecasters say it will head north, along that open corridor, to the mid-Atlantic states. Here's the latest advisory on Nicole.
The current storm track takes it straight toward Baltimore. And along the way it will be swept up by the final component in this sprawling weather event, the coastal storm that is expected to form off the Southeastern states Wednesday night.
As the tropical moisture is drawn north along the Atlantic corridor, it will run into the Appalachians and the cold front parked to our west, unloading all that tropical rainfall on us. Expect periods of torrential rains, strong and gusty winds, possible thunderstorms or tornadoes. The region is also likely to experience power outages as trees and limbs succomb to the weather and tear down wires as they fall.
The good news is that much of the East Coast really needs a big dose of rain. But we don't need flooding and we don't need people skidding off wet roads or driving into overflowing streams. So the other bit of good news is that by the time it gets here, this system will be moving north pretty fast, minimizing the time it spends unloading its water on us.
Jeffrey Halverson, an associate professor of environmental science at UMBC, offers this analysis of what's ahead:
"My commentary, after studying charts and reading various discussions, this AM:
"1. The models are still having trouble with regard to placement of the heavy rain axis, and we are now [less than] 24 hours from the onset of a major event. There may be a tendency for some models to push heavy rain too far to the NW, away from the coast. Nor have the models successfully predicted the very early arrival of the moist air mass, now pushing up through Richmond toward Baltimore.
"2. Widespread 2" - 4" with higher amounts seems likely along and east of the I-95 corridor.
"3. There are two components to this system that are expected to phase: (a) the deep tropical mositure plume which includes remnants of [Nicole]; and (b) the closed upper low over the SE US with a lingering frontal boundary along the coast. This upper-level low - which is distinctly non-tropical in origin - is expected to form a new coastal low somewhere in the vicinity of NC-VA, which will then draw in and process the tropical plume.
"Heavy rains over our area will come from three elements: (1) the tropical plume gliding up over the coastal front; (2) uplift provided by the remnants of [Nicole]; and (3) the developing coastal low." Here's more from the Maryland Emergency Management Agency:
The Maryland Emergency Management Agency urges Maryland residents to make preparations.
The storms could lead to power outages, and residents are urged to have an emergency supply kit with water, food, a flashlight and a battery operated radio or weather radio. Residents should monitor local news broadcasts for updates and those living in areas subject to flooding (low-lying areas, areas along streams and creeks) should be prepared to evacuate if needed.
When driving in such conditions, motorists are reminded to never drive through standing water because several inches of fast moving water can carry a vehicle down stream. TURN AROUND, DON’T DROWN.
If your area is under a tornado warning, move quickly to the basement or an interior room away from windows and doors. If you cannot get into a building, lie flat in a ditch or on low ground and cover your head with your hands.
For more information on preparedness, go to the following web sites:
"http://www.mema.state.md.us/">and click on be prepared, which will take you to pages for general preparedness, flooding and other natural disasters (which includes a section on tornado preparedness.
"http://www.ready.gov/">which has detailed information on assembling emergency kits and creating a family emergency plan.
"http://www.redcross.org/">and click on the Preparedness and Getting Trained tab, then the Preparedness Fast Facts link.
For more information, contact Ed McDonough, MEMA public information officer, at 410-517-3632 (office) or 410-446-3333 (cell).