Predictions and forecasts are being made for the 2013 Hurricane Season months prior to any tropical activity and will listed below as more information becomes available.
This outlook reflects an expected set of conditions that is conducive to above-normal Atlantic hurricane activity. These conditions are based on three climate factors:
The tropical multi-decadal signal, which has contributed to the high-activity era in the Atlantic basin that began in 1995.
A continuation of above-average sea surface temperatures in the tropical Atlantic Ocean and Caribbean Sea (called the Main Development Region).
ENSO-neutral conditions most likely (no El Niño or La Niña), with lingering La Niña impacts into the summer.
In addition, several dynamical model forecasts of the number and strength of tropical cyclones generally predict an above normal season.
The conditions expected this year have historically produced some active Atlantic hurricane seasons. Therefore, the 2011 season could see activity comparable to a number of active seasons since 1995. We estimate a 70% probability for each of the following ranges of activity during 2011:
12-18 Named Storms
3-6 Major Hurricanes
An ACE range of 105%-200% of the 1981-2010 median
The seasonal activity is expected to fall within these ranges in 7 out of 10 seasons with similar climate conditions and uncertainties to those expected this year. These ranges do not represent the total possible ranges of activity seen in past similar years.
The official NHC seasonal averages are 11 named storms, 6 hurricanes, and 2 major hurricanes.
It only takes one storm hitting your area to cause a disaster, regardless of the overall activity predicted in the seasonal outlook. Therefore, residents, businesses, and government agencies of coastal and near-coastal regions are urged to prepare every hurricane season regardless of this, or any other, seasonal outlook.
While NOAA does not make an official seasonal hurricane landfall outlook, the historical probability for multiple U.S. hurricane strikes, and for multiple hurricane strikes in the region around the Caribbean Sea, increases sharply for exceptionally active (i.e. hyperactive) seasons (ACE > 165% of the median). However, predicting where and when hurricanes will strike is related to daily weather patterns, which are not reliably predictable weeks or months in advance. Therefore, it is currently not possible to reliably predict the number or intensity of landfalling hurricanes at these extended ranges, or whether a given locality will be impacted by a hurricane this season.
Tropical depressions, tropical storms and hurricanes are low pressure areas that develop in the tropical regions of the ocean (between 20 degrees N latitude and the equator). These storms are masses of thunderstorms that organize and begin to rotate. These systems, in order of intensity, are called depressions (winds between 25 and 38 mph), tropical storms (winds between 39 and 73 mph) and hurricanes (winds of 74 mph or greater).
The National Weather Service tracks these storms on charts during hurricane season, June 1 through Nov. 30, using the following symbols.
A tropical depression, the lowest intensity, is given a number once it has a counterclockwise spin and winds of 38 mph or less.
When wind speeds reach 39 mph and the storm is given a name from a pre-determined list, a tropical storm is born. While a tropical storm does not produce a high storm surge, its thunderstorms can still pack a dangerous and deadly punch. In 1972, Agnes was only a tropical storm when it dropped torrential rains that led to devastating floods in Pennsylvania, Maryland and Virginia. Sixteen people died in Virginia and damage was estimated at $222 million.
A hurricane is the most intense tropical event, with five categories and winds ranging from 74 mph to 155 mph or greater. Storm surge is a major concern with hurricanes. The extremely high winds cause ocean water to pile up, creating higher than normal sea levels with waves up to 40 feet in open water. High sea levels and shallow waters can devastate a coastline and bring ocean water miles inland.
A hurricane's bands of thunderstorms produce torrential rains and sometimes tornadoes. A foot or more of rain could fall in less than a day, causing flash floods and mudslides. Large rivers in the hurricane's path might still be flooding for days after the storm has passed. The storm's driving winds can topple trees, utility poles and damage buildings. Communication and electricity might be lost for days and roads are often impassable due to fallen trees and debris.
The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf and the shape of the coastline, in the landfall region. Note that all winds are using the U.S. 1-minute average.
Category 1 Hurricane
Winds 74-95 mph (64-82 kt or 119-153 km/hr). Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days. Hurricane Lili of 2002 made landfall on the Louisiana coast as a Category One hurricane. Hurricane Gaston of 2004 was a Category One hurricane that made landfall along the central South Carolina coast.
Category 2 Hurricane
Winds 96-110 mph (83-95 kt or 154-177 km/hr). Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks. Hurricane Frances of 2004 made landfall over the southern end of Hutchinson Island, Florida as a Category Two hurricane. Hurricane Isabel of 2003 made landfall near Drum Inlet on the Outer Banks of North Carolina as a Category 2 hurricane.
Category 3 Hurricane (major)
Winds 111-129 mph (96-112 kt or 178-208 km/hr). Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes. Hurricanes Jeanne and Ivan of 2004 were Category Three hurricanes when they made landfall in Florida and in Alabama, respectively.
Category 4 Hurricane (major)
Winds 130-156 mph (113-136 kt or 209-251 km/hr). Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months. Hurricane Charley of 2004 was a Category Four hurricane made landfall in Charlotte County, Florida with winds of 150 mph.Hurricane Dennis of 2005 struck the island of Cuba as a Category Four hurricane.
Category 5 Hurricane (major)
Winds greater than 157 mph (137 kt or 252 km/hr). Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months. Only 3 Category Five Hurricanes have made landfall in the United States since records began: The Labor Day Hurricane of 1935, Hurricane Camille (1969), and Hurricane Andrew in August, 1992. The 1935 Labor Day Hurricane struck the Florida Keys with a minimum pressure of 892 mb--the lowest pressure ever observed in the United States. Hurricane Camille struck the Mississippi Gulf Coast causing a 25-foot storm surge, which inundated Pass Christian. Hurricane Andrew of 1992 made landfall over southern Miami-Dade County, Florida causing 26.5 billion dollars in losses--the costliest hurricane on record. In addition, Hurricane Gilbert of 1988 was a Category Five hurricane at peak intensity and is the strongest Atlantic tropical cyclone on record with a minimum pressure of 888 mb.
Know if you live in an evacuation area. Know your home's vulnerability to storm surge, flooding and wind. Have a written plan based on this knowledge.
At the beginning of hurricane season (June 1st), check the supplies for your disaster supply kit, replace batteries and use food stocks on a rotating basis.
During hurricane season, monitor the tropics.
Monitor NOAA Weather Radio. It is an excellent / official source for real-time weather information and warnings.
If a storm threatens, heed the advice from local authorities. Evacuate if ordered.
Execute your family plan.
A HURRICANE WATCH issued for your part of the coast indicates the possibility that you could experience hurricane conditions within 36 hours. This watch should trigger your family's disaster plan, and protective measures should be initiated, especially those actions that require extra time such as securing a boat, leaving a barrier island, etc.
A HURRICANE WARNING issued for your part of the coast indicates that sustained winds of at least 74 mph are expected within 24 hours or less. Once this warning has been issued, your family should be in the process of completing protective actions and deciding the safest location to be during the storm.
The Atlantic hurricane season runs from June through November. During that period, eastern Virginia is especially at risk for a major storm.
For more hurricane information for Virginia, go to VDOT's hurricane evacuation guide site.