When talking about hurricanes, and examining them over history, there arises a distinct category of the storm that sets itself apart from easy comparison to the rest. Hurricanes have impacted the gulf shores and east coast alike, but over time a pattern has emerged that give a hurricane that makes its way up to New England several unique qualities, different from a more quintessential storm of more expected qualities down south.

You can see all the hurricanes that have impacted New England in the last 400-years by clicking here...As with all hurricanes, high winds, storm surge, and heavy rains are associated with these storms...but some things stand out specifically when talking about these storms.

David Vallee is the Hyrdologist-in-Charge at the Northeast River Forecast Center, co-located with the National Weather Service office in Taunton, Massachusetts. He has been researching the idiosyncrasies of New England hurricanes for years, and is an expert in their character. My expanded interview with him gave a good picture into the nature of these storms.

All Hurricanes Created Equal..?

For the most part, Vallee explains hurricanes that strike New England begin like any other hurricane, "born in the tropics". This refers to a variety of places, though the common spots are all south of the latitude of the Bahamas. Though it has happened, the birthing grounds for a hurricane that makes it to New England typically isn't the Western Caribbean or the Gulf of Mexico (sometimes a storm can curve all through all these areas on it's way up the coast). Usually it's the warm late-Summer waters around the Bahamas, or the south Atlantic Ocean extending all the way to the Cape Verde Islands just off the African coast (hence the 'Cape Verde Storm'). These storms would grow, strengthen, and plod along similarly to others of it's kind. "Usually around the time the storms get to the Bahamas, they have a decision to make," Valley says. "Are they going to go into the Gulf, curve out to sea, or will they make that uncommon route, and go right up the east coast."

Getting a Hurricane to New England

"It takes a very unique series of events to get a storm up here...A very anomalous pattern...way outside the realm of what would be 'normal'." David Vallee goes on to describe some specific requirements of the surrounding environment-- covering upper air currents east of the Mississippi straight over into the open waters east of Bermuda-- that all have to be in sync to get the job done. Though it's a rare event, most of the time it does happen, there's a jet-stream pattern that almost looks like it belongs in February, "a very deep trough along the east coast...basically helps to capture the hurricane, and drive it into New England". Sometimes there's some conspiring going on, where an area of high pressure (known for their sunny weather and blocking patterns), will sit over the entire Atlantic, just east of the coastline, and never offer an outlet for a northward moving storm. Other times, there's simply a very stingy storm system hanging out over the Great Lakes, and a hurricane heading northward finds it simply too attractive to curve away from. When more than one of these effects are at work, the results are often give a hurricane the added element of surprise (because it's going much faster).

Forward Speed, Rain Pattern, and Wind Field Differences

"New England Hurricanes accelerate rapidly...the average forward motion of a gulf hurricane is 10-12mph, In New England it is a remarkable 33mph" It is not only this forward speed that is an essential element to a hurricane that maintains itself close to New England, but also the acceleration. Instead of a storm impacting the same state for days (as with Tropical Storm Fay impacting Florida in the Summer of 2008), hurricanes in New England are like a bull-in-a-china-shop, barely lingering around more than 12-hours. There have been storms that have approached New England at hurricane strength, but undergo significant weakening before making landfall, even if they were quite strong while passing the Carolinas (for example, hurricane Belle, 1976). The waters north of the Carolinas are not in the Gulf Stream current, and are most often not warm enough to strengthen a storm-- which means it will aid in its weakening. A quickening forward speed will minimize the time a storm spends over these waters, and thus minimizes it's weakening before landfall. As a storm starts to move rapidly northward, they no longer look like a textbook hurricane, "instead of a classic 'buzz-saw' shape, the forward movement causes an elliptical shape, oriented toward the direction of motion."

When a typical hurricane impacts an area, the strongest winds and heaviest rains are said to be around the core of the storm, in the eye-wall. As it moves overland, the rainfall would be concentrated along the track of the storm, with comparatively lesser amounts to either side. Dave Vallee explains, "In a New England Hurricane, most heavy rainfall is along and to the west of the center." The distinction is rather remarkable, as this axis of heavy rain that appears with a land-falling hurricane in the Northeast can actually orient itself more than 100 miles from the center. There are some cases in which storms actually put most of its rainfall well to the center of its track, but perhaps those times a storm has tracked so far west of the area, that the rainfall observed well to the east was swept in by the shifting wind field of the storm, together with a coastal front, and in some spots the added benefit of elevation (for example, hurricane Connie, 1955)

As for the wind-field, when a storm moves in, most of the heavy gusts occur to the east of the center. Along the coast, you would have less frictional influence on the wind-speeds as you would inland, but these winds can migrate well to the east of the storms center. As a consequence, wind gusts can be practically negligible to the west of the storm center. With hurricane Bob, in 1991, gusts up to 125mph were reported from Block Island, RI to Truro and Brewster on Cape Cod, but west of I-495, winds seldom made it over 40mph. Also with a New England hurricane, the wind-field is modified east of the center by its forward speed. When you think about it, if there's a 50mph wind blowing from a storm that itself is moving at 50mph, there's got to be at least some sort of additive property. "As a crude rule of thumb, an area due experience this core of sustained winds can add the forward motion to the sustained wind speed. This sum gives an estimate of maximum gust potential". Consider hurricane Gloria in 1985. As the hurricane was preparing to make landfall, it was undergoing significant weakening (much like hurricane Belle a few years earlier). However, this storm was moving at 50mph, which minimized the amount of time away from the incubating tropics until landfall. Not only was it able to maintain hurricane-force winds at landfall, but, well east of the center, gusts over 110mph were experienced at the Blue Hill Observatory, in Milton, MA. Similar additive gust potentials were seen in other fast moving storms, including the "Long Island Express" of 1938.

The storm surge with a New England Hurricane can be best described as 'sneaky'. As with any land-falling storm, a typical surge can be calculated mathematically, with the highest potential east of the center (or with the case of a prototypical storm, to the right of track movement). The New England coastline presents a unique set of hazards with regards to storm surge, the multitude of bays an inlets perforating the coast can allow the surge itself to be channeled inland, to heights of 20-feet or more over places like Buzzards Bay, the Narragansett, and the upper Sakonnet River.

A Hurricane In Transition

"It just so happens that a hurricane is trying to become Winter-like as it interacts with the jet-stream," David Vallee says. Perhaps the best way to compare it would be to think of the Blizzard of '78 as a hurricane, and a New England Hurricane like a blizzard, because there's surprisingly little difference in their wind fields, axis of maximum precipitation, or even the location of surge and coastal flooding. But, one is a blizzard and one's a hurricane...so why so similar?

When a hurricane crosses the latitude of the Carolinas, it naturally would start to lose strength. A hurricane requires at least 80° water temperatures generate the amount of evaporation/condensation moisture content in the air above the ocean surface suitable for a hurricane's needs. The strongest hurricanes actually require a little more, as they're hungrier. From Cape Hatteras to the New England shores, the waters aren't as warm. So if a storm wanted to maintain itself solely in the style of a hurricane engine, it's simply not going to be able to.

"The winds in the tropics are very gentle." Vallee explains. They aid a tropical hurricane's strengthening by staying out of the way. For the 'Noreaster on the other hand, the winds from the surface on up are quite violent in nature, allowing the storm to push massive amounts of air around itself. Two types of storms, similar conditions on the ground, two different engines. It has been shown that with major hurricane impact, the storms that have been able to survive (and perhaps even thrive), do so by amazingly transitioning internally from one energy source to another; from a purely tropical animal, to one with blizzard-like characteristics. This was first documented in New England through the careful re-analysis of the Great Hurricane of 1938.

With hurricanes that strike New England, it can be said there are a series of steps that a storm would migrate through in it's track up the coastline. Some storms are fully along it, others are somewhere in the middle, and still others may still yet be full fledged hurricane-quality events. Obviously the foundational stage for any of these storms is one of a hurricane, complete with it's internal tropical characteristics and (at least) quasi-symmetry of wind/moisture. Here the storm would either be in a growth, or at least sustaining environment. Eventually, this storm would migrate into tropically unsupportable conditions (colder water temperatures, shear, upwelling, etc.)...this arena could be called one of tropical weakening. Here, the environment for hurricanes is not favorable, and a storm would necessarily weaken. Some storms obviously never make it out of this stage, but often, given the right conditions, a storm may either speed through this zone, or skip right over it into an area of extratropical transition. This category is reached by many hurricanes migrating toward New England, especially in the September-October months, whereas the environment for a June-July storm would result more often in plain dissipation. This transition is built on necessity for a strong storm's continual survival, as it changes it's energy sources to include the upper-air and surface manifestations of cyclonic (baroclinic) instability. Storms in transition are sometimes more dangerous than an actual hurricane of similar intensity. The wind-field expands remarkably, though asymmetrically favoring the eastern side. Likewise the western half of the system starts to concentrate rainfall. Internal surface fronts begin to form and channel the movement of air masses. The forward speed will also pick up, decreasing warning-time and increasing wind gusts. Depending on the time spent in a weakening environment, the forward speed of a storm, and the amount of time it takes for the 'transition' to take place, storms can actually intensify rapidly and remarkably during this phase, though they seldom reach the strength attained in their past tropical peak. It also appears that storms that spend the longest time incubating over tropical waters, for our purposes the so-called 'Cape Verde' storms (that form off the African coast and can spend more than a week in perfect tropical conditions as hurricanes before transitioning), have internal cores that are the most hardy toward adversity. If they are able to migrate from tropical zones to ones that favor extratropical transitioning, they thrive pretty quickly, and remain quite powerful. The Great Hurricane of 1938, Hurricane Donna (1969), and Hurricane Gloria (1985) are all examples of this type of storm. This process of 'transitioning' continues, until the generated surface fronts effectively lift all the original tropical air, even to the core of the storm, and thus reaches an occlusion stage. From this point forward, the storm no longer has any tropical characteristics, and would be considered similarly to a powerful 'Noreaster or other open-sea cyclone.

Variation In Frequency over Decades

"For us up here in the Northeast, what is normal depends on what the temperature of the Atlantic Ocean is like," David explains, "From the 1930s to the 1960s, New England was threatened by a hurricane almost every other year...Then from the 1960s to the mid 1980s we weren't." Studies have come to show that just as hurricane numbers in the Atlantic have varied over the years, so too have the average ocean surface temperatures. It certainly stands to reason that the preponderance of the foundational building block for hurricanes (warm ocean water) would naturally lead to the formation of more of them. David Vallee describes this current period of Atlantic ocean temperature as another 'warm' point in the cycle (similar to the 30s-60s). "This multi-decadal signal of this warm Atlantic...helps to breed more hurricanes and because the ocean and atmosphere are intrinsically connected...it drives the weather patterns...it drives the steering currents. So I say, with a warmer Atlantic, we should expect more hurricanes to approach the Atlantic coast...because it's that warm Atlantic that gets them to grow (and) adjust the jet streams...to be more favorable to bring storms to New England."

"Sometimes it's predictable...sometimes it's not so predictable...that's why we here in New England need to be ready at the start of the season, regardless."