Northeast Weather Blog

Irene takes aim on *Northeast*

By: sullivanweather, 3:06 PM GMT on August 25, 2011

Current watches, warnings and advisories.


Eastern US current watches/warnings
Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

Your Northeast Forecast

Synopsis


All eyes are on Irene this morning as it churns over the Bahamas as a category three major hurricane. This storm has the Northeast in its crosshairs this weekend, promising to bring flooding rainfall, damaging winds and high storm surges along the coast. Before Irene's arrival there will be a couple of systems to deal with; the first today in the form of a fairly decent cold front bringing the chance for isolated severe thunderstorms and heavy rainfall and the next on Saturday as another possible area of heavy rainfall indirectly associated with Irene moves up along the coastal plain. As Irene chugs into Canada early Monday morning a much cooler and drier airmass will filter in and last till Wednesday, giving the region a chance to clean up and dry out.


Short-term forecast


A sharp trough and its associated cold front will slide across the Northeast today, shearing out in the process as it meets up against a strong offshore deep-layer ridge of high pressure. This is the same ridge responsible for steering Hurricane Irene towards the East Coast. Out ahead of this front deep moisture is streaming northward on a brisk 30-35kt low-level jet, pumping precipitable water values around the 2" range, so it's a rather humid start to the day for much of the region. Also streaming northward ahead of the front along a pre-frontal trough is an area of widespread showers and embedded thunderstorms moving through central Pennsylvania and New York. Rainfall with these storms have been heavy this morning, with some places picking up over an inch of rain. This area of precipitation will gradually shift eastward as the day progresses, reaching eastern New York and Western New England around lunchtime and slowing considerably thereafter. Visible satellite imagery shows extensive cloud cover over much of the region save the immediate coast, so insolation will not be too big a role in heating things up in this humid airmass. This should limit the severe weather threat but it will still be present. Instability should easily reach 1,000J/kg along the coastal plain, yielding plenty of energy for convection. As the pre-frontal trough moves towards the coast expect a new round of storms to fire up this afternoon from southeastern Pennsylvania to southern New England while further west along the actual cold front, more scattered convection and maybe a forced narrow line of storms will continue to fire until it passes by So another round may be in store for areas of central Pennsylvania to the Finger Lakes region. Further to the north over central/northern New England cloud cover will keep surface instability low but it will be made of aloft as a strong push of positive vorticity moves trough associated with the mid-level disturbance, providing the extra lift needed for scattered showers and thunderstorms here as well. The front will have a bit more progression the further north one heads so rainfall won't be nearly as heavy across the North Country. However, along the coast as the flow aloft aligns to the front expect this feature to slow down and stall, providing an ideal set-up for training thunderstorms and flash flooding given the wet antecedent conditions. Rainfall amounts should range from a quarter to three quarters of an inch to the north with a half into to an inch and a half to the south with possibly higher amounts in training thunderstorms. High temperatures will be in the 70's for most areas today, though some upper 60's are possible given the quicker onset of thicker clouds over the higher elevations of the North Country while sections of extreme southern New Jersey, where some breaks of sun occurred this morning, temperatures might climb into the low 80's. It will be quite muggy in all areas except for the far northwestern portion of the region where the cold front has passed.

The front reaches just offshore and stalls out tonight as showers and thunderstorms taper off in the evening hours. Otherwise expect partly to mostly cloudy skies and a slow drying of the airmass across the northern third of the region. To the south it will remain muggy with low temperatures in the mid 60's to low 70's. To the north, mid 50's to low 60's should do.

On Friday the humidity begins to creep back north as the front along the coast washes out. There will be more sun than clouds, especially over the interior, but overall a very nice day. There's an outside chance for an isolated shower across southern New Jersey where moisture will be a bit deeper but that's it. A great day to make preparations for the arrival of Irene this weekend. Temperatures will run a few degrees above normal with highs reaching into the mid to upper 70's across the north with low to mid 80's south.

It's the calm before the storm Friday night as Irene will be approaching the Outer Banks of North Carolina at this time from the south. Over the Northeast, 500-700 miles north of the storm, signs are there may be a predecessor rainfall event developing over New Jersey, southeastern New York and southwestern Connecticut. Should this occur there will be some very intense rainfall associated with very slow-moving thunderstorms which may cause localized flash flooding concerns. Elsewhere expect mainly partly cloudy skies and temperatures on the mild side, running 5-10 degrees above normal.



Mid-term forecast


As the weekend begins there will be a steady deterioration of the weather from south to north in most areas east of the I-81 corridor. For those west of this region the forecast is fairly straight forward. Expect a veil of high cloudiness to move over the region on Saturday, sticking around all weekend. In the far west these high clouds will be thin, allowing for a greater diurnal swing in temperatures from the upper 70's during the day to the mid 50's at night. The clouds will thicken the further east one heads, knocking a few degrees off daytime high and keeping overnight lows a few degrees warmer. Cloud cover will begin to diminish Sunday night as a dry, brisk westerly breeze develops in the wake of Irene.

For areas along and east of I-81 it will be a harrowing weekend. Pre-event will be ongoing during the early morning hours on Saturday for areas along the coastal plain up to Connecticut. Rainfall associated with the pre-event will generally range from a quarter to a half inch but localized areas which see training storms could easily pick up three inches or more. Keep in mind this will be the one last day to complete preparations for Irene. High clouds will be on the increase throughout the day, lowering and thickening across areas to the south by the afternoon. Cape May, County, New Jersey may even begin to see the first outer bands of Irene move in before dusk. Winds will begin to increase out of the east, beginning the day in the 10-15mph range along the coast (5-10 inland) and increasing to 15-25mph along the coast by evening (10-15 inland).

By Saturday night Irene will be starting to make her presence felt as the outer rainbands begin to spread over the coastal plain of New Jersey and back across southeastern Pennsylvania during the evening hours. By this time Irene should be passing the mouth of the Chesapeake, pounding the Tidewater region with hurricane conditions. Irene will also begin to accelerate north at this time as she becomes embedded within the mid-latitude flow. This will allow for a quicker northward expansion of precipitation after midnight, reaching Long Island, extreme southern New England, southeast New York and eastern Pennsylvania before daybreak. Further north expect just a continuation of increasing cloudiness ahead of Irene. Temperatures will be quite warm as the tropical airmass moves over the region with most places across the interior remaining in the mid 60's while areas along the coast remain in the low 70's.

Sunday will be a day many youngsters will one day tell their grandkids about. Hurricane Irene will begin the day about 25 miles off the coast of Chincoteague, Virginia, heading just east of due north for western Long Island. The model guidance for Irene's track has come into much better agreement with clustering over the western portion of Long Island as the storm gets captured by a strong southerly flow between a very powerful deep-layer ridge over the western Atlantic Ocean and a digging shortwave trough over the Great Lakes. On this track Irene promises to bring hurricane conditions for a huge section of real estate as the storm hugs the Jersey shore then slams ashore Long Island by the evening hours. Irene's impact will be felt far and wide and will be detailed here and in the tropical section of the blog. Temperatures will remain in the 70's for most areas with upper 60's over the higher terrain.

Irene's impacts



Wind




Due to Irene's expected girth as the storm moves north along the coast it is unimportant to pay attention to where the center comes ashore in this situation as her effects will be felt far and wide. Irene will have a strong massive wind field that will bring hurricane force wind speeds for most of the coastline from Cape May to Cape Cod. For inland locations, hurricane force winds will be felt in areas up to 40 miles east of the center and 25 miles west of the center until the storm spins down to a tropical storm up to 150 miles inland over New England. Additionally, just about all of New England, eastern New York, New Jersey and eastern Pennsylvania will see at least tropical storm force winds sustained or in gusts, depending on how far one is from the center. The stronger winds will be felt on the east semi-circle of the storm. Higher elevations over 2000' will also see hurricane force wind gusts due to the circulation remaining strong aloft. Highly populated cities susceptible to seeing hurricane force winds include New York City (especially the boroughs of Queens and Brooklyn);Atlantic City, New Jersey; Hartford, Connecticut; Springfield, Massachusetts and Providence, Rhode Island. Once again, due to Irene's large and well-developed circulation the potential wind impact from Irene will be maximized. Unlike smaller, less-developed tropical systems where the wind field is sporadic and concentrated to localized areas, Irene's will be much more widespread and take much longer to dissipate. This means bad news for areas across the interior as much of this area has been in a wet pattern this month, leaving soils saturated and trees vulnerable to be toppled by the wind.



Rainfall



Despite how severe of a wind event Irene will bring to the coast, perhaps the biggest impact from Irene will be the excessive rainfall and inland flooding. As mentioned, the antecedent conditions are extremely wet. Some areas are already approaching their record wettest August and these includes stations around since 1955, when two tropical systems affected the Northeast. The frontal system will bring up to an inch of rainfall today and the pre-event has the potential to bring much more all before the arrival of Irene. Irene will be non-typical of a Northeast hurricane caught in the mid-latitude flow as it won't be zooming through the region as most of these storms do. Instead it will make a steady progression through the Northeast around 15-20 mph; fairly quickly, but relative to a Northeast hurricane, a graceful stroll. Thus, Irene will be capable of producing extremely heavy rainfall amounts.

Now that it appears Irene will track just east of due north after passing the Carolinas, the hurricane will take a more western track than anticipated yesterday. This will expand the rain coverage much further west than anticipated yesterday. As the storm interacts with land much of the convergence will occur on the west side of the hurricane due to the frictional component of the land as opposed to the eastern side of the storm, which will be over the water. This increasing angular momentum within the storm will cause Irene to become lopsided, with most of the heaviest rainfall occurring on the western semi-circle of the storm. Not an odd occurrence but certainly bad news for the Northeast as it spreads out Irene's wrath, with flooding rainfall west and stronger winds east. Rainfall amounts will range from 6-10"+ for areas up to 100 miles west of the track of the center with amounts quickly tapering west of there. Along the track of Irene and for areas up to 25 miles east of the track of the center 4-8" of rainfall will be common. For the remainder of New England rainfall amounts should range from 2.5-5". In all areas these amounts are enough to bring just about every waterway out of their banks; creeks, streams and main stem rivers. Should there be excessive rainfall with the pre-event prior to Irene flooding of historic proportions are possible across areas of northern New Jersey, northeastern Pennsylvania, southeastern New York and Connecticut.



Storm Surge



While it is too early for specific area storm surge forecasts due to track of Irene, timing of high tide, etc., a general picture is emerging for what we can expect to see from Irene's storm surge. For areas where the center comes ashore and up to 50 miles east expect a storm surge of at least 6-10' above expected tides. Some of the narrow bays may even see tides up to 15' above expected tides, which would be of historic proportions. Should a landfall occur on Long Island even areas east of the maximum zone of storm surge as far east as Cape Cod will see storm surges of 4-8' above expected tides. Areas further up the New England Coast should see a 2-4' storm surge. Along the New Jersey Coast storm surge of 3-5' is expected but should the storm take an inland track (a slight possibility) this could easily be doubled. It must be repeated that these are extremely preliminary estimates, however, residents along the South Shore of Long Island should seriously consider evacuations now as they are right in the bullseye.


Long-range Outlook



After the passage of Irene much cooler air will enter the Northeast as a mainly dry trough digs into the region. Across the North Country, Irene, undergoing extra-tropical transition, will provide lingering heavy rainfall in the morning, tapering to upslope showers by afternoon. Elsewhere skies will gradually clear and winds will be brisk out of the northwest. High's will range from the 50's across the north to the 70's south. Seasonable weather continues Tuesday and Wednesday with mainly dry weather. Heights build to close out the week as temperatures climb back above normal with continued mainly dry conditions.

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Tropical Update


Coming soon...



IR Satellite image of Hurricane Irene.






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Radar: Northeast Region Loop

NE radar
Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Tropics, Forecast

Updated: 3:12 PM GMT on August 25, 2011

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Northeast prepares for Irene

By: sullivanweather, 2:52 PM GMT on August 24, 2011

Current watches, warnings and advisories.


Eastern US current watches/warnings
Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

Your Northeast Forecast

Synopsis


The Northeast region will be treated to stunning late-summer weather this Wednesday (hopefully no earthquakes) before a cold front delivers another round of strong to severe thunderstorms on Thursday. A nearly undetectable short-wave ridge will provide enough subsidence for a pleasant Friday, which should be taken as a day of preparation for the arrival of Irene for residents within 150 miles of the coast. By Friday night Irene will be bearing down on the Outer Banks of North Carolina from Atlantic Beach to Cape Hatteras, headed north or north-northeast toward our region. Well out ahead of Irene will be a predecessor rain event (PRE) across a portion of the Northeast, from eastern Pennsylvania to southern New England, while most everywhere else escapes any precipitation. This weekend Irene begins to accelerate up the coast with gradually deteriorating conditions throughout the day Saturday for areas along the coastal plain and hurricane conditions possible by Saturday night and Sunday from Delaware to Maine. Heavy rain and flooding, damaging winds, and storm surge and beach erosion are all expected to accompany Irene, which stands a good possibility of becoming the first landfalling hurricane in the Northeast in 20 years. Following the storm, an area of high pressure nosing down from Canada will provide several days of cool, dry weather to allow for clean-up to commence.


Short-term forecast


A stunning day across much of the Northeast today so get out and enjoy it. Mostly sunny skies for most areas east of the Appalachians, though there will be some passing high cloudiness. Further west, cloud coverage will be a bit more widespread and some scattered showers or thunderstorms are possible in these areas by mid to late afternoon ahead of a cold front pushing towards the region. Temperatures will run a few degrees above normal and humidity levels will rise as the day progresses thanks to a breezy southwesterly return flow around a departing offshore high pressure. As this high gives way to the cold front moving in from the Great Lakes region, cloudiness will continue to increase into the evening and overnight hours. Showers and thunderstorms will become more numerous across the west and push into central Pennsylvania and the Finger Lakes region by daybreak. The increasing cloud cover and humidity will keep temperatures quite mild tonight, with 70's expected along the coastal plain and 60's across the interior.

Yet another round of heavy rain and severe weather is expected on Thursday From eastern New York and Pennsylvania to western New Englan, pushing across the remainder of New England Thursday night. Although my previous forecast had indicated there would be a lack of instability due to cloud cover on Thursday it now appears that enough sun will break through during the morning hours to adequately destabilize the warm, humid airmass ahead of the front before it sweeps through. CAPE's reach up to 1,500J/kg along the coastal plain with 500-1,000J/kg across the interior. Primary severe threats will be large hail up to 1.5" in diameter and strong thunderstorm winds via wet microburst. Heavy rains will also be a concern. Precipitable water values reach up to 2" out ahead of the front, which will be in the process of stalling as it aligns to the upper-level flow. This will make for training and/or slow-progressing thunderstorms capable of flash flooding, especially in rain-soaked regions from New Jersey to southern New England. Likelihood of such storms will increase towards evening as the front slows. Most of the activity will slide offshore a little after midnight. Highs on Thursday will be in the upper 60's across the higher terrain with low 70's to near 80°F expected across the remainder of the North Country and back towards the Great Lakes region. Further south highs will range from the upper 70's to mid 80's. Lows will remain elevated Thursday night along the coast with cloud cover hanging around. Expect upper 60's to low 70's here with upper 50's to mid 60's over the interior.

Friday will be a day of contrast across the Northeast as the coastal plain sees a rather warm, muggy day in the vicinity of the washed-out front with filtered sunshine and temperatures in the 80's. Further north the airmass will be cooler and drier with more abundant sunshine and temperatures in the upper 60's to mid 70's. The canopy of high clouds from Hurricane Irene will quickly spread from south to north starting early afternoon across New Jersey and reaching the Capitol District of Albany by dusk.



Mid-term forecast


The first effects of Irene will begin to be felt by Friday night across New Jersey and southeastern Pennsylvania as moisture streaming up the coast ahead of the storm reaches the old washed-out front still hanging around. This will cause heavy showers and thundershowers to develop and become more widespread as a predecessor rainfall event develops. Predecessor rainfall events (Pre-event) are quite a common occurrence in recurving tropical systems. Pre-events are notorious for having very localized areas of 4-6" of rainfall and this one should be no different. A combination of a rich tropical moisture transport, jet dynamics, positive vorticity and a pre-existing trough will lead to yet another round of heavy rains over areas that have been repeatedly hit this month and are about to get their heaviest rain yet when Irene arrives. To the north and west Irene's shield of clouds will gradually envelope the entire region, lowering and thickening during the overnight. As the flow turns back onshore humidity will rise and the air will begin to acquire the smell of the ocean as saltine air rides inland. Lows will be several degrees above normal with the increasingly muggy conditions.


As the weekend begins the pre-event will be tracking northward into New York and southern/western New England as Hurricane Irene, either after making landfall over the Outer Banks of North Carolina or just brushing them by, tracks toward Long Island. The outer rainbands of the hurricane itself will begin to impact southern New Jersey by mid-afternoon so all preparations and/or evacuations should take place by Saturday morning at the very latest for areas along the Jersey Shore. Elsewhere it will be mostly cloudy and muggy with high temperatures in the 70's region-wide.

The real show begins Saturday night as Irene moves from a position just offshore the Tidewater region of the lower Mid-Atlantic during the evening to about 40 miles east of Cape May, New Jersey by midnight and 25 miles south of central Long Island by daybreak Sunday. Hurricane conditions can be expected along the Jersey Shore for a 4-6 hour period during Irene's closest approach with tropical storm conditions as far west as eastern Pennsylvania and across nearly all of interior New Jersey up to New York City. In Long Island conditions will steadily deteriorate as the night progresses with tropical storm conditions likely by midnight and hurricane conditions likely by early Sunday morning. Across Long Island Sound into southern New England the first outer bands should be felt by midnight with tropical storm conditions likely by morning. The further one lives away from the coast the less likely it is they will see much from Irene. This appears to be a hard-hitter for those within 100-125 miles of the coast but west of here Irene will be a cloudstorm. During the day on Sunday Irene continues to accelerate to the north-northeast, crossing southern New England and finally into Maine by late in the evening. Irene is likely to be downgraded to a tropical storm sometime either late Sunday afternoon or Sunday evening over New England but will still remain quite a storm for the North Country of New Hampshire and the North Woods of Maine.

Irene's impacts will be felt greatest along the coast and will be detailed further in a future blog as the exact track gets nailed down. Generally, expect a 6-10' storm surge to the east of where the center comes ashore with a 2-5' storm up the Jersey Shore, across Long Island Sound and west of where the center comes ashore, presumably, in Long Island. Rainfall will be quite intense with 3-8" along the track of the cyclone, heaviest in a band just to the northwest of the center. Sustained hurricane force winds along the coast from New Jersey to Cape Cod are a good bet and may occur inland of the coast to the east of the center's landfall (southeastern southern New England). To the west of the storm's track up to 75 miles tropical storm conditions are a good bet as well, with possible gusts to hurricane force with 25 miles of the center. The strength of this wind on loaded trees, rooted in already saturated ground is a recipe for many fallen trees and power outages. There's a good chance this storm will rival any other before it in the number of customers who lose power due to the high population density of the region this storm is hitting and the antecedent conditions.



Long-range Outlook


High pressure builds down from Canada behind Irene bringing a taste of fall to the Northeast with crisp nights and dry, sunny afternoons both Monday and Tuesday. A little bit of moisture sneaking into the region next Wednesday may spark off a few scattered showers and thunderstorms across the southern half of the region but most areas will remain precipitation-free. Temperatures will average 4-7 degrees below seasonal averages.

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Tropical Update


Coming soon...



IR Satellite image of Hurricane Irene.



Track forecast for Hurricane Irene







Intensity forecast for Irene







Wind impact equivalent from Irene








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Radar: Northeast Region Loop

NE radar
Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Tropics, Forecast

Updated: 9:05 PM GMT on August 24, 2011

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It's time to prepare for Irene

By: sullivanweather, 1:16 PM GMT on August 22, 2011

Current watches, warnings and advisories.


Eastern US current watches/warnings
Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

Your Northeast Forecast

Synopsis

A strong early-season cold front is currently sweeping through Maine after producing a widespread severe weather outbreak across the Northeast on Sunday. There were multiple reports of flooding from training thunderstorms across New Jersey and Long Island yesterday as well as numerous power outages across Vermont, mainly in Rutland County, where strong thunderstorm winds toppled many trees. A much more comfortable airmass will be left in the wake of the front today through Wednesday before another front makes it way towards the region from the Great Lakes. This front will be one of several that will help to carve a trough across the Great Lakes region that will lift Atlantic Hurricane Irene up the Eastern Seaboard at the end of the week into the weekend. More detailed information on Hurricane Irene will follow the Northeast Forecast in the Tropical Update section of the blog. At this time it appears areas within 150 miles of the coast stand a good chance of dealing with Irene in some capacity. Flooding rainfall will be the most likely and widespread effect felt here in the Northeast but should this hurricane take a track further east than models currently indicate winds and storm surge will become an ever increasing threat. After Irene lifts into the Canadian Maritimes yet another trough/upper low will dig into the Great Lakes, sending another cold front towards the Northeast to begin next week.


Short-term forecast


Rain and embedded thundershowers will exit Maine during the morning hours as a strong cold front clears the region leaving behind a much drier and cooler regime over the next 36-48 hours. Outside of a few instability/orographic showers scattered across Upstate New York and Northern New England, the remainder of the region will see partly sunny skies with a crisp northwest wind of 10-20mph. Daytime temperatures will average close to seasonal normals along the coastal plain but will drop below normal across the higher terrain across the North Country as clouds and showers develop with the cold pool of air aloft and still strong August sunshine. Definitely a feel of autumn in the air today and even more so tonight. Skies will clear and winds will slacken as high pressure moves overhead. Temperatures will plummet under ideal radiational cooling conditions. Expect lows across the interior to drop into the 40's with a 38 or 39 degree reading possible in the normally colder locales such as Saranac Lake. Temperatures will not get as cold across the coastal plain with 50's likely for most and 60's in the urban areas.

A beautiful day is expected for Tuesday as high pressure crests over the region during the morning hours and slides offshore by afternoon. This high will bring mostly sunny skies and very comfortable humidity levels during the afternoon hours to go along with high temperatures right where they should be for late August; upper 60's across the higher terrain of the North Country with 70's across the remainder of the interior and low to mid 80's along the coastal plain.


Mid-term forecast


Southwesterly flow increases Tuesday night and Wednesday as a cold front approaches from the Great Lakes. Warm air advection and increasing high cloudiness from the west will keep temperatures about five to ten degrees warmer than the night before. Likewise for Wednesday, as high temperatures push into the upper 80's along the coastal plain with increasing humidity levels, with upper 70's to mid 80's across the interior and mid 70's across the North Country. A couple renegade thundershowers may run far enough out ahead of the front to affect western Pennsylvania and New York before sunset but most precipitation will hold off till the overnight hours.


The next cold front will move into the Northeast Wednesday night but will not be nearly as strong as the front this weekend. Hence, more scattered precipitation is expected along its flakes with severe weather virtually nil Wednesday night. Most of the rainfall associated with the front Wednesday night will remain across the northwestern half of the region, where lows will dip into the low to mid 60's. The Southeastern half of the region will simply see increasing cloudiness with mild readings remaining in the 70's across the coastal plain with mid to upper 60's points inland.


Long-range Outlook


The aforementioned cold front will slowly sink towards the coast on Thursday with scattered showers and thunderstorms, most concentrated across the North Country, closest to the parent area of low pressure. Severe weather will be isolated at best as morning cloudiness should stamp out most instability and winds aloft aren't all that impressive. With clouds and showers expected temperatures should run about 4-8 degrees below normal for afternoon highs but it will be quite humid in all areas but the far northwest. Upon reaching the coast the frontal boundary is expected to stall and eventually wash out Thursday night into Friday thanks to building heights over the Western Atlantic as deep-layer ridging anchored over Bermuda builds west. This will help to steer Hurricane Irene towards the US mainland and likely as a significant, if not, major hurricane. How strong the ridging is will ultimately determine its eventual track but all residents from Florida to Maine are not in the clear as of yet. With pleasant weather expected for much of the week leading up to the arrival of Irene, now is the time to get prepared! Residents living along the coast should pay extra close attention to the very latest on Irene's track as they will be directly affected by the worst of the storm (strong winds/storm surge). Residents away from the coast in low lying or flood-prone areas also need to start preparations now. It's been a very wet month thus far and many area rivers are running at above normal levels for this time of year. Additionally, water tables are quite high as are soil moisture contents so it will not take much more rainfall to initiate flooding. This needs to be kept in mind, especially if the storm makes landfall in the Southeast because the rainfall with this system will still cause flooding concerns despite the weakened nature of the storm overall. This is a very dangerous situation as the last hurricane to directly make landfall in the Northeast was Bob in 1991, a full twenty years ago. Plenty of complacency can build over twenty of years.

Should Irene continue on a path model guidance suggests the western half of the region should escape most of this storm. However, the eastern half of the region could be in store for a very wet and wild weekend. Indirect rainfall from Irene in the form of a 'pre-event' appears likely to develop on Saturday. A weak trough draped across the region will help to initiate showers and thunderstorms during the afternoon, which should be slow-moving and quite moisture-laden, hence, flash flooding is a good possibility. Synoptic set-up will favor areas from central Pennsylvania to central New England as candidates for these storms. Otherwise expect increasing high cloudiness as the outflow canopy associated with Irene advances on the region. Increasing easterly flow off the Atlantic will start to kick up some stronger breezes along the coast as the saltine air invades the region ahead of Irene. Showers directly associated with Irene will begin to increase during the afternoon hours across southern New Jersey and Delaware. Temperatures will be warm, with highs in the 70's and 80's region-wide, and humidity levels will increase as the day progresses.

Saturday night through Monday will be game on for Irene and the Northeast. A western track will spare the region most of the stronger winds and storm surge but sustained tropical storm force winds should be expected up and down the coast and occur inland in gusts. However, the big story would be the rainfall as the stalled trough over the region serves of a focusing mechanism for enhanced convergence. As the deep tropical moisture feed and strong forcing associated with Irene pull into the region rainfall will get rather intense. Preliminary estimates are for three to as much as eight inches along the coastal plain with one to five inches across the interior. This type of rainfall would easily send small creek and streams as well as main stem rivers out of their banks. A more eastern track to the cyclone, clipping the Carolinas, would send the hurricane barreling towards the region as a very strong entity. Should this occur it would be likely that a good portion of the Northeast Coast will see hurricane force winds, with strong tropical storm force winds extending inland a good distance. At this time it is the scenario of lowest probability but it is a distinct possibility. As mentioned earlier, it has been twenty years since the last direct hit from a hurricane in the Northeast and a hurricane of the potential magnitude of Irene hasn't been felt since Hurricane Donna of 1960. There's an outside chance of this being a generational storm so there's many alive today where this will be a first time event. Something to take note of.



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Tropical Update


As of the 9AM AST National Hurricane Center advisory, Hurricane Irene was located at 19.0°N, 67.2°W, or 90 miles west-northwest of San Juan, Puerto Rico. Maximum sustained winds are up to 80mph with higher gusts although the pressure has risen slightly to 990mb. Movement is to the west-northwest at 14mph.



IR Satellite image of Hurricane Irene.



Irene has made some strides overnight and subsequently become the season's first hurricane at 5:50 this morning, as per NHC updated statement. Radar presentation of the storm has greatly improved, with a distinct eye now visible on both radar and, occasionally, on satellite. Outflow is restricted to the west and southwest of Irene as the hurricane continues to encounter 10-15kts of wind shear across the western semi-circle of the cyclone. To the north and east outflow is extremely impressive. Excellent poleward venting of the storm is noted, which then dips rapidly into a strong upper-level low pressure developing in the wake of the system across the central Atlantic. This wind shear is allowing for some dry air to be ingested by the storm, as evidence by the pulsing convection in the inner-core and the inability, thus far, for Irene to build a complete eyewall. Currently, the storm is over sea-surface temperatures of 28.5-29°C, plenty warm enough to support continued slow intensification in the near-term, as long as the shear remains in the 10-15kt range. Now that it is apparent that Irene will steer north of Hispaniola, land interaction will be less of a deterrent as well.

Wind shear in the 10-15kt range will continue to affect the cyclone through Tuesday afternoon, disrupting any rapid intensification possibilities and keeping Irene a category two storm at most. At this time the cyclone will be entering the region of the Turks and Caicos islands and the southeastern Bahamas and slowing down in forward speed as it continues on its west-northwesterly course, so a prolonged period of hurricane conditions will begin to affect the island archipelago that should last up to 24 hours in any given location along the storm's path.
By Tuesday night and Wednesday wind shear will begin to relax as upper-level high pressure develops over the eastern half of the storm and deep-layer ridging in the vicinity of Bermuda builds west. This should signal a period of further intensification that should bring Irene up to major hurricane status by the time it reaches the central Bahamas. Steering currents should begin to direct Irene on a northwesterly course by this time as another trough dips into the Northeastern region of the country, providing a weakness for the storm to move into.

Irene will continue to remain a impressive, major hurricane as it approaches the Southeast Coast Thursday and Friday after lashing the northern Bahamas. Indications as that Irene will grow in size to occupy quite a bit of real estate off the Southeast Coast. As Irene moves into the weakness along the East Coast it will begin to take on a more northerly component in its forward motion but confluent flow to the north of the storm will further slow its forward speed to an agonizing crawl. Moisture streaming out ahead of the storm in the form of rain squalls will begin to brush the coastal areas beginning on Thursday across Florida and by Friday from Georgia to the Carolinas. From this point forward, where the storm moves will be determined by the strength of the trough dipping into the Great Lakes region of the country. A stronger trough will tend to recurve Irene quicker, lessening chances for a landfall from South Carolina to Florida, but increase chances from North Carolina to the Northeast. A weaker trough will allow Irene to continue to the north-northwest into Georgia or South Carolina. Florida isn't out of the crosshairs yet but enough of a weakness should be present to allow Irene to pass by to the east. Stayed tuned, Florida. Either way, chances of a landfalling hurricane somewhere along the East Coast is about 80%, so now is the time to commence preparations.




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Radar: Northeast Region Loop

NE radar
Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Hurricane, Northeast forecast

Updated: 4:29 AM GMT on August 23, 2011

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Last week's heavy rain and Harvey approaching hurricane strength

By: sullivanweather, 11:54 AM GMT on August 20, 2011

The Rainfall which fell on the region last Friday night was particularly heavy along the coastal plain, where development of a coastal front/low pressure aided in low-level convergence. Cold air moving in aloft in the form of a very tightly would (especially for August) mid/upper-level low pressure system promoted convective elements within the overall shield of heavy rain, combined with unidirectional flow, this led to some rather impressive totals.


NASA MODIS Terra image of the Northeast on August 14th depicting a convective band of heavy rain along the coast.

Rainfall totals tapered inland, further removed from best forcing/moisture but 1-4" totals weren't uncommon up the Hudson Valley and points east into interior New England. Here's a brief rundown of some of the higher rainfall totals over the last four days:

Lido Beach, NY - 10.87"
Seabrook Farms, NJ - 10.64"
Wantagh, NY - 10.54"
West Islip, NY - 9.18"
Oceanside, NY - 8.75"
JFK Airport - 7.80" (all-time greatest daily rainfall - 8/14)
Central Park, New York City, NY - 6.37"
Lyndhurst, NJ - 6.00"



How does this event stack up against historical extreme rainfall events across the region?

April 2007 nor'easter

The last such widespread extreme rainfall event for the region affected by this latest system occurred during the April 2007 nor'easter, a slow-moving intense nor'easter which will be mostly remembered for the heavy wet snow dumped across upstate New York, northeast Pennsylvania and interior New England. But this storm did have a very wet side to it and the rainfall totals across the coastal plain were quite impressive, especially for a cold-season system. Rainfall totals as a whole were very similar over much the same area as what occurred this past weekend. However, due to the stratiform nature of the precipitation rainfall amounts were more evenly distributed than with this most recent event.


Radar rainfall estimates of precipitation during the April 2007 nor'easter

Rivervale, NJ - 9.30"
Central Park, New York City, NY - 8.41"
East White Plains, NY - 8.22"
West Shokan, NY - 7.43"
Lambertville, NJ - 7.25"
Somerset, NJ - 6.73"
Bakersville, CT - 6.72"
Roxborough, PA - 6.22"

Upton WFO PNS report of April 2007 nor'easter
Mt.Holly write-up/PNS of April 2007 nor'easter

However, for the Northeast as a whole, there's been other even more impressive rainfall events over the last ten years which make the latest event pale in comparison. June of 2006 was one such event.

June 2006 flooding





Over a 6 day timespan (24-29th) an oscillating band of heavy rain moved into the Northeast, hitting Pennsylvania and New York the hardest. Record river crests occured at many gauge sites on all 3 main stem rivers in this area (Deleware, Hudson and Susquehanna) as 5-14" of rain fell. Along the Deleware River the flooding was particulaly bad with many locations receiving a '100-year flood'.

June 2006 precipitation departures
Binghamton, NY Case Study: June 2006 Flood
Binghamton, NY June 2006 Flood page(including photos, precipitation estimate graphics and river gauge data)
Plot of rainfall amounts - New Jersey, eastern and central Pennsylvania, southeast New York, Deleware and northeast Maryland.

October 2005 flooding

Just eight months prior to the big June of 2006 flood, in October of 2005, there was a very similar atmospheric set-up which led to the most recent rainfall event; a slow-moving series of upper level disturbances moving over an area of high tropical moisture and numerous low-level convergent boundaries. This pattern repeated over a period of more than a week with two separate rainfall events, one from October 7-9th and the next from the 11-15th. Up to a foot of rainfall fell during the first system across parts of southeast New York while the second system, or series of systems, produced another widespread 5-15" of rain across the region. Central Park finished the month with 16.73", just short of breaking the all-time monthly record for rainfall of 16.85" set way back in September of 1882.

Upton WFO PNS of the Oct 7-9th event
Upton WFO PNS of the Oct 11-15th event

Flooding of late summer 2004

The most impressive widespread monthly rainfall over the Northeast over the last ten years, and on record, occurred during a period spanning August and September of 2004. The flooding was due to a series of 5 remnant tropical systems: Gaston, Hermine, Francis, Ivan and Jeanne. Each one of these systems produced some level of flooding and created wet antecedent conditions for the following systems, exacerbating the flooding problems.


Graph showing Northeast region rainfall since 1895. Note 2004 recorded the record highest basin-wide rainfall for the period of record with an 11.48" average.



Gaston

Gaston rainfall amounts

Although Gaston affected the region in late August, it layed the groundwork to what the pattern would be like the the rest of the month, remnant tropical systems interacting with cold frontal boundaries to produce copious amounts of rainfall.

Gaston made landfall as a category 1 hurricane along the South Carolina coast. The storm then turned northward, then northeastward and exited the coast near Ocean City, Maryland and continued out to sea. Although the storm never made a direct impact on the Northeast, the moisture from this system became entrained into a cold front to produce localized rainfall amounts of 3-6 inches causes numerous flash floods.

Major flash flooding took place in Westbrookville, NY, a small village along the Sullivan County/Orange County border in southeast New York. Large sections of US route 209 were washed away along with many mobile homes in a trailer park. Further north in upstate New York the counties of Onondaga, Cayuga, Madison and Steuben all received significant flash flooding.


Hermine

Hermine was a weak tropical storm which moved ashore Massachusetts on the last day of August. For the most part Hermine was a non-entity, producing up to 2 inches of rain over eastern Long Island and southeastern Massachusetts. There were some reports of minor basement flooding but that was the extent of her damage. Hermine formed from the same trough of low pressure that formed Gaston and oddly enough made landfall in the general vicinity as Hurricane Carol did 50 years prior.


Frances

Hurricane Frances

Frances was a long-lived Cape Verde hurricane that made 2 U.S. landfalls in Florida. One as a category 2 hurricane and another as a tropical storm in the Panhandle. The storm then turned towards the north and rode the west side of the Appalachian Mountains along a cold front before moving up the St. Lawrence River Valley.

Most of the rainfall from Frances that fell on the Northeast fell across the western half of the area with a few localized spots in southeast New York receiving heavy amounts of rain as well. Across western sections of New York and Pennsylvania 3-6" of rain fell, which brought sharp rises to areas rivers and brought some flashier creeks and streams out of their banks.

For the rest of the Northeast Frances brought a soaking rainfall which prepped the ground for Ivan, which followed one week later. There was one other area of heavy rainfall from training convection ahead of the cold front in southeast New York State which hit Orange, Putnam, Dutchess and Ulster counties hard, bringing flash flooding.

Rainfall amounts from Frances in my local area.
National Hurricane Centers' tropical cyclone report on Frances


Ivan

Northeast rainfall totals from Ivan

Ivan was another long-lived Cape Verde hurricane which reached category 5 on 3 different occasions and accumulated the 2nd highest ACE for any Atlantic hurricane on record. Ivan made landfall on the Gulf Coast of the U.S. moved northward to the central Applachians before turning east, moving offshore the Delmarva. Ivan lost tropical characteristics overland, but once offshore the East Coast, moved southward before looping back towards the west. The remnants of the system then moved over Florida where it gradually regained tropical characteristics before becoming a tropical storm yet again in the Gulf of Mexico, making its final landfall in Louisianna.

For the Northeast, Ivan brought widespread heavy amounts of rain. Almost the entire state of Pennsylvania received 3 inches of rain or more, with several locations getting as many as 7 inches. With wet antedecent conditions from Gaston and Frances, flooding became a major issue. Many small streams and creeks as well as main stem rivers were brought out of their banks due to the excessive amounts of rain on saturated soil.

NWS Local forecast office links:

NWS Binghamton, NY

Radar rainfall estimates
Flooding photos
Damage reports/spotter reports

NWS Albany, NY

Multi-sensor precipitation estimate

NWS Upton, NY (NYC)

Spotter rainfall reports

NWS Tuanton, MA

24 hour rainfall 9/18/2004
24 hour rainfall 9/19/2004

NWS Mt. Holly, NJ (Philadelphia area)

Ivan rainfall page
Includes a plotted rainfall map and Public Information Statement

NWS State College, PA

Ivan Storm Summary
-This is a very informative link on the impacts of Ivan on central Pennsylvania. This link includes an in depth storm summary(text), plotted rainfall map, individual spotter reports, satellite and radar imagery, tornado reports and river stage charts for many gauge locations including river crests from Ivan, historical record crests and a comparison to the January 1996 flood.


Jeanne

Northeast rainfall amounts - Jeanne

Jeanne developed from a tropical wave just east of the Lesser Antilles and eventually became a category 3 hurricane, striking Florida in the same spot as Hurricane Frances 3 weeks prior. Jeanne followed an unusual path, seemingly headed out to sea after turning north, north of Hispainola. However, a strong high developed to Jeannes' north, blocking this cyclone from recurving and eventually turning her towards the U.S. East Coast. Jeanne, after making landfall, stayed inland moving up the Floridian Peninsula and up the east side of the Appalachian Mountains before moving offshore the Delmarva Peninsula.

In the Northeast rainfall from Jeanne was not as widespread as Ivan or Frances, but with saturated ground areas that did recieve rainfall quickly flooded. For the most part rain was confined to the southeastern half of the Northeast with the Philadelphia-New York City metro area hardest hit with totals of 4-7". This stripe of heavy rain continued eastward across Long Island, Nantucket, Martha's Vineyard and Cape Cod.

Jeanne related links:

HPC Jeanne Rainfall synopsis

NWS WFO State College, PA
Another very informative look into Jeannes' impacts across central Pennsylvania.

NWS WFO Mt. Holly, NJ
Includes a radar estimated precipitation map, tornado information and storm damage photos.

NWS WFO Upton, NY
Pubilc Information Statement detailing spotter reported rainfall amounts.

NWS WFO Taunton, MA
24 hours rainfall 9/29/2004
24 hour rainfall 9/30/2004



Current watches, warnings and advisories.


Eastern US current watches/warnings
Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.


-------

Tropical Update

As of the August 20th 4AM CDT National Hurricane Center advisory, Tropical Storm Harvey is located at 16.4°N, 86.5°W, with a westerly forward motion at 12mph. This location places the center about 10 miles northeast of Roatan Island, north of the Honduras coast. Maximum sustained winds have strengthened to 60mph, with higher gusts, and central pressure has dropped to 994mb.


Tropical Storm Harvey in the western Caribbean Sea.

A very strong burst of convection developed over the center of Harvey during the overnight hours, with cloud tops approaching -85°C, clearly indicating that Harvey is taking advantage of the improved surrounding environment. Strong convection also exists in a cyclonically curved band in the northern semi-circle of Harvey rotating into the developing central dense overcast. Outflow is good to excellent in all but the western quadrant where confluent flow is restricting the expanding high cloud canopy over the Yucatan. Atmospheric moisture is no longer a problem as Harvey's convection has successfully mixed out any remaining dry air.

It is now becoming increasingly likely that Harvey will attain hurricane strength before making landfall between Monkey River Town and Dangriga along the Belize Coast. As mentioned above, conditions are universally conducive for development with high atmospheric moisture content, upper-level high pressure, warm sea-surface temperature around 29°C, and despite the close proximity to land the topography of the region actually fosters development of tropical cyclones. So I'm expecting Harvey to reach 75-80mph, a minimal hurricane and the season's first, before landfall early this afternoon close to the border of the Toledo and Stann Creek districts. After landfall Harvey should quickly begin to weaken and should be downgraded to a depression by early Sunday morning. With strong deep-layer ridging over Texas Harvey shouldn't emerge over the Bay of Campeche and should continue on a westward track into the mountainous terrain where it will dissipate.

Harvey's main impact to the region will be in the form of extremely heavy rainfall over the mountainous terrain of Guatemala. Winds along the coast may cause minimal damage but buildings in the region are built to withstand a minimal hurricane. Storm surge along the coast will be in the 3-5' range so minor beach erosion will be possible but there shouldn't be any damage to the fragile coral reefs offshore.


------------

In the deep tropics there are two disturbances drawing attention at this time. One is about 400 miles east of the Leeward Islands on the Eastern Caribbean and is of most interest at this time. Over the last four days this tropical wave has slowly gained convection but has recently began to tighten its broad low-level cyclonic flow as a tropical depression appears to be in the early stages of formation.


Tropical disturbance '97L'

Currently the tropical wave lies within a region of broad upper-level divergence to the northeast of a fairly weak upper-level low pressure system over northern South America which is aiding in the development of moderate to strong convection along the wave axis and in several cyclonically curved bands feeding into the presumed developing center of circulation. This preliminary fix on this center is 15.5°N, 55.5°W, which appears to be elongated northwest to southeast.

Dry air surrounding the wave has been slowly mixing out as it heads west and shouldn't be any hindrance to further development from this point forward. Sea-surface temperatures are very warm, 0.5 to 1°C above normal, about 28.5 to 29°C, along the future projected path of any cyclonic development and increase to over 30°C from the Bahamas to the Florida Straits right across the Gulf of Mexico. These temperatures are about as warm as it gets in these basins so should development occur there will be plenty of potential heat energy available.

Global models do, in fact, develop this disturbance into a tropical cyclone and take the system across the Greater Antilles from Sunday night through Wednesday morning. During this time development will be a struggle as the system encounters about 10-20kts of southwesterly wind shear due to a lingering upper-level trough through early Tuesday. Proximity to land will also be a problem for intensification so development beyond a storm of tropical storm force doesn't appear likely before Wednesday. Although chances are this system will remain weak as it crosses the islands, rainfall with this system will be particularly intense. The lingering upper trough over the Caribbean will make for increased vertical instability, hence, very strong convection. Also, the forward motion of the system will be less than 10kts so it will have plenty of time to dump flooding rainfall. Where the heaviest rainfall will focus will depend ultimately on the track of any potential cyclone but amounts exceeding 25" in the hardest hit areas is entirely likely. This would lead to severe flooding and mudslides, especially over deforested and destructed Haiti.

After moving past the islands Wednesday night or Thursday the upper-level environment will become very conducive for development as an anti-cyclone develops and establishes itself over the cyclone. As mentioned earlier sea-surface temperatures are very warm in the region of Florida, over 30°C, so a period of rapid intensification could very well occur. There's also indications of this storm growing in size to become a very large entity. With a trough of low pressure in the mid-latitudes moving by to the north the size and vertical structure of the storm will likely govern its future track. A bigger and stronger storm will likely move north faster and possibly take a track up the East Coast. A smaller and weaker storm will likely be less influenced by the passing trough and could turn back towards the west into the Gulf of Mexico. This may all be a moot point should the storm fail to develop but indications are something will develop and will have a major role in the nation's weather this weekend on into early next week.




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Radar: Northeast Region Loop

NE radar
Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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extreme rainfall, past weather, tropics

Updated: 2:29 PM GMT on August 20, 2011

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Recent extreme rainfall comparison

By: sullivanweather, 6:49 AM GMT on August 17, 2011

The very slow moving upper-level disturbance which has brought extremely heavy rainfall over the Northeast during the previous four days is finally lifting out into the Canadian Maritimes early this morning. A short-lived period of tranquility will return for Wednesday, with mostly sunny skies and temperatures returning to seasonable levels. A fairly weak trough will glide into the region on Thursday and remain till Friday, sparking off widely scattered, slow-moving showers and thundershowers during the afternoon and evening hours. Over the weekend, a deeper trough will dig into central Canada, shifting the mean flow to the southwest which will bring warmer and more humid air into the Northeast with further isolated, diurnally-driven showers and storms. The Canadian trough will sharpen further to open next week as it moves east, sending a strong cold front towards the region that has the potential for a more widespread severe weather outbreak Monday afternoon and evening. This front will make slow but steady progress through the region, however, a solid one to two inches of rain may accompany this front along with the severe potential. The front clears New England by Tuesday evening with drier, autumn-like air back for midweek.

The Rainfall which fell on the region since Friday night was particularly heavy along the coastal plain, where development of a coastal front/low pressure aided in low-level convergence. Cold air moving in aloft in the form of a very tightly would (especially for August) mid/upper-level low pressure system promoted convective elements within the overall shield of heavy rain, combined with unidirectional flow, this led to some rather impressive totals.


NASA MODIS Terra image of the Northeast on August 14th depicting a convective band of heavy rain along the coast.

Rainfall totals tapered inland, further removed from best forcing/moisture but 1-4" totals weren't uncommon up the Hudson Valley and points east into interior New England. Here's a brief rundown of some of the higher rainfall totals over the last four days:

Lido Beach, NY - 10.87"
Seabrook Farms, NJ - 10.64"
Wantagh, NY - 10.54"
West Islip, NY - 9.18"
Oceanside, NY - 8.75"
JFK Airport - 7.80" (all-time greatest daily rainfall - 8/14)
Central Park, New York City, NY - 6.37"
Lyndhurst, NJ - 6.00"



How does this event stack up against historical extreme rainfall events across the region?

April 2007 nor'easter

The last such widespread extreme rainfall event for the region affected by this latest system occurred during the April 2007 nor'easter, a slow-moving intense nor'easter which will be mostly remembered for the heavy wet snow dumped across upstate New York, northeast Pennsylvania and interior New England. But this storm did have a very wet side to it and the rainfall totals across the coastal plain were quite impressive, especially for a cold-season system. Rainfall totals as a whole were very similar over much the same area as what occurred this past weekend. However, due to the stratiform nature of the precipitation rainfall amounts were more evenly distributed than with this most recent event.


Radar rainfall estimates of precipitation during the April 2007 nor'easter

Rivervale, NJ - 9.30"
Central Park, New York City, NY - 8.41"
East White Plains, NY - 8.22"
West Shokan, NY - 7.43"
Lambertville, NJ - 7.25"
Somerset, NJ - 6.73"
Bakersville, CT - 6.72"
Roxborough, PA - 6.22"

Upton WFO PNS report of April 2007 nor'easter
Mt.Holly write-up/PNS of April 2007 nor'easter

However, for the Northeast as a whole, there's been other even more impressive rainfall events over the last ten years which make the latest event pale in comparison. June of 2006 was one such event.

June 2006 flooding





Over a 6 day timespan (24-29th) an oscillating band of heavy rain moved into the Northeast, hitting Pennsylvania and New York the hardest. Record river crests occured at many gauge sites on all 3 main stem rivers in this area (Deleware, Hudson and Susquehanna) as 5-14" of rain fell. Along the Deleware River the flooding was particulaly bad with many locations receiving a '100-year flood'.

June 2006 precipitation departures
Binghamton, NY Case Study: June 2006 Flood
Binghamton, NY June 2006 Flood page(including photos, precipitation estimate graphics and river gauge data)
Plot of rainfall amounts - New Jersey, eastern and central Pennsylvania, southeast New York, Deleware and northeast Maryland.

October 2005 flooding

Just eight months prior to the big June of 2006 flood, in October of 2005, there was a very similar atmospheric set-up which led to the most recent rainfall event; a slow-moving series of upper level disturbances moving over an area of high tropical moisture and numerous low-level convergent boundaries. This pattern repeated over a period of more than a week with two separate rainfall events, one from October 7-9th and the next from the 11-15th. Up to a foot of rainfall fell during the first system across parts of southeast New York while the second system, or series of systems, produced another widespread 5-15" of rain across the region. Central Park finished the month with 16.73", just short of breaking the all-time monthly record for rainfall of 16.85" set way back in September of 1882.

Upton WFO PNS of the Oct 7-9th event
Upton WFO PNS of the Oct 11-15th event

Flooding of late summer 2004

The most impressive widespread monthly rainfall over the Northeast over the last ten years, and on record, occurred during a period spanning August and September of 2004. The flooding was due to a series of 5 remnant tropical systems: Gaston, Hermine, Francis, Ivan and Jeanne. Each one of these systems produced some level of flooding and created wet antecedent conditions for the following systems, exacerbating the flooding problems.


Graph showing Northeast region rainfall since 1895. Note 2004 recorded the record highest basin-wide rainfall for the period of record with an 11.48" average.



Gaston

Gaston rainfall amounts

Although Gaston affected the region in late August, it layed the groundwork to what the pattern would be like the the rest of the month, remnant tropical systems interacting with cold frontal boundaries to produce copious amounts of rainfall.

Gaston made landfall as a category 1 hurricane along the South Carolina coast. The storm then turned northward, then northeastward and exited the coast near Ocean City, Maryland and continued out to sea. Although the storm never made a direct impact on the Northeast, the moisture from this system became entrained into a cold front to produce localized rainfall amounts of 3-6 inches causes numerous flash floods.

Major flash flooding took place in Westbrookville, NY, a small village along the Sullivan County/Orange County border in southeast New York. Large sections of US route 209 were washed away along with many mobile homes in a trailer park. Further north in upstate New York the counties of Onondaga, Cayuga, Madison and Steuben all received significant flash flooding.


Hermine

Hermine was a weak tropical storm which moved ashore Massachusetts on the last day of August. For the most part Hermine was a non-entity, producing up to 2 inches of rain over eastern Long Island and southeastern Massachusetts. There were some reports of minor basement flooding but that was the extent of her damage. Hermine formed from the same trough of low pressure that formed Gaston and oddly enough made landfall in the general vicinity as Hurricane Carol did 50 years prior.


Frances

Hurricane Frances

Frances was a long-lived Cape Verde hurricane that made 2 U.S. landfalls in Florida. One as a category 2 hurricane and another as a tropical storm in the Panhandle. The storm then turned towards the north and rode the west side of the Appalachian Mountains along a cold front before moving up the St. Lawrence River Valley.

Most of the rainfall from Frances that fell on the Northeast fell across the western half of the area with a few localized spots in southeast New York receiving heavy amounts of rain as well. Across western sections of New York and Pennsylvania 3-6" of rain fell, which brought sharp rises to areas rivers and brought some flashier creeks and streams out of their banks.

For the rest of the Northeast Frances brought a soaking rainfall which prepped the ground for Ivan, which followed one week later. There was one other area of heavy rainfall from training convection ahead of the cold front in southeast New York State which hit Orange, Putnam, Dutchess and Ulster counties hard, bringing flash flooding.

Rainfall amounts from Frances in my local area.
National Hurricane Centers' tropical cyclone report on Frances


Ivan

Northeast rainfall totals from Ivan

Ivan was another long-lived Cape Verde hurricane which reached category 5 on 3 different occasions and accumulated the 2nd highest ACE for any Atlantic hurricane on record. Ivan made landfall on the Gulf Coast of the U.S. moved northward to the central Applachians before turning east, moving offshore the Delmarva. Ivan lost tropical characteristics overland, but once offshore the East Coast, moved southward before looping back towards the west. The remnants of the system then moved over Florida where it gradually regained tropical characteristics before becoming a tropical storm yet again in the Gulf of Mexico, making its final landfall in Louisianna.

For the Northeast, Ivan brought widespread heavy amounts of rain. Almost the entire state of Pennsylvania received 3 inches of rain or more, with several locations getting as many as 7 inches. With wet antedecent conditions from Gaston and Frances, flooding became a major issue. Many small streams and creeks as well as main stem rivers were brought out of their banks due to the excessive amounts of rain on saturated soil.

NWS Local forecast office links:

NWS Binghamton, NY

Radar rainfall estimates
Flooding photos
Damage reports/spotter reports

NWS Albany, NY

Multi-sensor precipitation estimate

NWS Upton, NY (NYC)

Spotter rainfall reports

NWS Tuanton, MA

24 hour rainfall 9/18/2004
24 hour rainfall 9/19/2004

NWS Mt. Holly, NJ (Philadelphia area)

Ivan rainfall page
Includes a plotted rainfall map and Public Information Statement

NWS State College, PA

Ivan Storm Summary
-This is a very informative link on the impacts of Ivan on central Pennsylvania. This link includes an in depth storm summary(text), plotted rainfall map, individual spotter reports, satellite and radar imagery, tornado reports and river stage charts for many gauge locations including river crests from Ivan, historical record crests and a comparison to the January 1996 flood.


Jeanne

Northeast rainfall amounts - Jeanne

Jeanne developed from a tropical wave just east of the Lesser Antilles and eventually became a category 3 hurricane, striking Florida in the same spot as Hurricane Frances 3 weeks prior. Jeanne followed an unusual path, seemingly headed out to sea after turning north, north of Hispainola. However, a strong high developed to Jeannes' north, blocking this cyclone from recurving and eventually turning her towards the U.S. East Coast. Jeanne, after making landfall, stayed inland moving up the Floridian Peninsula and up the east side of the Appalachian Mountains before moving offshore the Delmarva Peninsula.

In the Northeast rainfall from Jeanne was not as widespread as Ivan or Frances, but with saturated ground areas that did recieve rainfall quickly flooded. For the most part rain was confined to the southeastern half of the Northeast with the Philadelphia-New York City metro area hardest hit with totals of 4-7". This stripe of heavy rain continued eastward across Long Island, Nantucket, Martha's Vineyard and Cape Cod.

Jeanne related links:

HPC Jeanne Rainfall synopsis

NWS WFO State College, PA
Another very informative look into Jeannes' impacts across central Pennsylvania.

NWS WFO Mt. Holly, NJ
Includes a radar estimated precipitation map, tornado information and storm damage photos.

NWS WFO Upton, NY
Pubilc Information Statement detailing spotter reported rainfall amounts.

NWS WFO Taunton, MA
24 hours rainfall 9/29/2004
24 hour rainfall 9/30/2004



Current watches, warnings and advisories.


Eastern US current watches/warnings
Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.


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Tropical Update

It's mid-August and the tropical Atlantic basin is sputtering to a start, despite a near-record pace in the number of named storms. Thus far all seven storms have failed to attain hurricane strength and most have been short-lived. The most recent rash of tropical storms, Franklin and Gert, barely achieved two ACE points between them, bringing the total for all seven storms to a measly 11.9.

There may be one more such storm in the offing, as a strong tropical wave (93L) currently entering the central Caribbean Sea has been showing signs of organization and could very well become the next named system. Strong cyclonic flow is noted on satellite loops in the mid-levels and should build down to the surface during increasing convective flare-ups over the next 12-24 hours as it moves into a region of higher moisture content. Wind shear across the Caribbean Sea is remarkably low and sea-surface temperatures are running 28-29°C, so there aren't too many obstacles in the way of future development.


Tropical disturbance '93L' in the central Caribbean Sea.

I expect a depression to be named from 93L by late tonight or early tomorrow morning, which will then become Tropical Storm Harvey by tomorrow afternoon. With high oceanic heat content, high levels of atmospheric moisture and low wind shear expected along the path of Harvey the cyclone should strengthen right until interaction with land, which will likely be Belize/Yucatan Peninsula. Whether or not 'Harvey' strengthens to a hurricane will be dependent on how quickly it can take advantage of the conducive environment before making landfall.

An upper-level low pressure to the southwest of the disturbance should continue its brisk pace towards the west into Central America with the tropical disturbance in hot pursuit. This westward motion of around 15kts should continue for the next 36 hours, with a slight bend to the north and a minor slowing of the forward speed. This track will take the possible tropical storm very close to the northeast coast on Honduras in 36 hours. From there a more west-northwest track is expected until crossing the Yucatan in 60-72 hours. With strong deep-layer ridge to the north over northern Mexico and the US Southern Plains this storm may not make it back into the Bay of Campeche and may instead be suppressed south into Mexico.


Elsewhere in the tropics, a well-defined tropical wave has just emerged off Africa which computer models have consistently developed into our first Cape Verde storm of the 2011 Atlantic Tropical Season. The GFS model in particular has this storm taking dead aim on the US mainland for several model runs straight. Broad cyclonic turning in the cloud field is noted with this wave with a cluster of moderate to strong convection south of the low center associated with the ITCZ. This will be definitely be something to keep an eye on over the next week to ten days.



_________________________________________________ __________


Radar: Northeast Region Loop

NE radar
Radar loop of the Northeast region. Courtesy of Weather Underground.


_________________________________________________ __________

Local SST's

Northeast SST's
Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


_________________________________________________ __________



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extreme rainfall, past weather

Updated: 12:23 PM GMT on August 17, 2011

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A brief review and your Northeast forecast

By: sullivanweather, 7:34 AM GMT on August 01, 2011

If there's one advantage to taking a break from blogging as long as I have; it makes for an easy recap. The winter was cold and snowy. The spring was beyond moist and the summer has been sizzling. How hot? How's does 108°F grab you on the tarmac at Newark Liberty Airport? Hot indeed, and three degrees hotter than the previous all-time record of 105°F. The Connecticut cities of Bridgeport and Hartford both broke their all-time record high temperatures, both recording 103°F. New York City's Central Park tied its 2nd hottest day ever at 104°F. The temperature at my backyard located in the pine forest foothills of the Catskill Mountains reached a blistering 95.6°F. Friday, July 22nd, 2011 will go down as one of the hottest days on record across the Northeast as a whole and one of three consecutive days of widespread 100°F heat with oppressive 80°F overnight "low" temperatures.

Records broken during heatwave of July 21-23, 2011

July 21st record high temperatures
July 21st record high minimum temperatures
July 22nd record high temperatures
July 22nd record high minimum temperatures
July 23rd record high temperatures

July 23rd record high minimum temperatures


What made this heat wave particularly intense were the incredible humidity levels. In conjunction with the Mississippi-like heat were Mississippi-like dewpoints in the upper 70's and low 80's. Even here the dewpoint briefly touched 80°F. The main culprit for such staggering amounts of atmospheric moisture associated with this heatwave was the equally staggering amount of precipitation which occurred during the springtime months over our region and all points upwind to the West Coast. I guess you can call spring 2011 flooding's Manifest Destiny. For the months of March-May the Northeast region as a whole saw its second wettest spring on record. Likewise for the Ohio and Mid-Mississippi Valley regions of the Country. Same for the Northern Plains and the Northern Rockies and not to be outdone, the Pacific Northwest recorded their wettest spring on record. The states of New York, Vermont and Pennsylvania also recorded their wettest spring on record and my tomatoes can attest to this fact.

Precipitation ranking by state for the period March-May.

Image showing statewide precipitation rankings for meteorological spring. Note many states broke their all-time record wettest spring from the Ohio Valley into the Northeast. (Credit: NCDC)

Precipitation ranking by region for the period March-May.

Image showing region-wide precipitation rankings for meteorological spring. Note the record to near-record precipitation across much of the northern half of the US. (Credit: NCDC)


The extremely wet spring heralded an early end to a seasonably cold and snowy winter for the southern two thirds of the Northeast, as heavy rains in early March quickly washed away the winter snowpack. The northern third of the region, for the second consecutive winter, saw mostly mild winter weather as a persistently highly positive phase of the Arctic Oscillation caused infiltration of maritime air on several occasions and kept most of the major blizzards south of the region. New York City's Central Park recorded its 2nd highest monthly snowfall total in January of 36.0" and 3rd highest seasonal snowfall total of 61.9".

Radar Image of December 26th, 2010 blizzard

Radar image showing the height of the Blizzard of December 26-27, 2010. Note the very heavy band of snow across northeastern New Jersey and the Hudson Valley of New York State. 20-30 inches of snow was common within this band, including New York City, which received 20.0" of snow at Central Park. (Credit: HPC/NOAA)


On a personal note (time for my little rant), these so-called blizzards (Dec. 26-27, 2010/Jan. 26-27, 2011) were the biggest tease snowstorms I ever did see. For all the hype, for all the state-of-emergencies, I received 4.1" and 3.2" respectively from those two storms. In fact my greatest snowfall of the "winter" occurred on March 23-24th with 7.9", more than those two storms combined! So, for this upcoming winter I'm expecting all those near-misses of last winter to be direct hits. And by expecting, I mean expecting like The Godfather expects things to get done...or else. In other words, I'm holding winter personally responsible should we not get at least three one-foot snowstorms. I don't know how I'll accomplish this but somehow us weather forecasters are viewed as conjurers of storms amongst some circles. So I'll see what I can do.


Northeast Weather Forecast

After the incredible high temperatures of last weekend a more seasonable pattern has taken shape over the last week for a majority of the Northeast. Most of the hot and oppressive weather has retreated south to the Mason-Dixon line where temperatures have continued to average in the 90's but elsewhere across the region a pattern more typical of mid-summer has taken hold - warm and mainly dry with a progressive pattern aloft bringing through several troughs and mid-levels disturbances to touch of scattered showers and thunderstorms. Once such trough is scheduled to move into the Northeast to begin the work week on Monday, with its parent mid-level low spinning down from Quebec to settle over Northern New England on Tuesday. Another disturbance will ride a quickening west-to-east flow into the region early on Wednesday and be accompanied by a stronger frontal boundary which should bring mainly dry and seasonable weather to the region to close out the week. Next weekend looks much more interesting as a trough drops down over the Northeast while a tropical disturbance approaches the East Coast. Chances are some deeper tropical moisture will be pulled into this trough axis giving the potential for heavy rains and downpours up and down the Eastern Seaboard.


Tropical Weather


Latest image of Atlantic Basin tropical disturbance '91L' (Credit: SSD/NOAA)


As of the August 2nd 5PM EDT National Hurricane Center advisory, the center of Tropical Storm Emily was located at 15.8°N, 65.4°W, moving west-northwest at 12mph. Maximum sustained winds have now strengthened to 50mph with higher gusts. Minimum central pressure is 1005mb.

The center of now Tropical Storm Emily formed very quickly yesterday evening near the island of Dominica and about 150 miles west of the mid-level center, which had been trying and failing to build down to the surface over the prior two days. Since forming, Emily has been able to maintain a central core of strong convection adjacent to the center of circulation. This convection has waned some earlier this afternoon but has now begun to reintensify, as evidenced by one overshooting thunderstorm top, and become consolidated closer to the center of circulation. Outflow is good to excellent in all quadrants, except the southwest quadrant where it's virtually non-existent.

The core of Emily is tucked right inside an area of high atmospheric moisture content with a warm sea-surface of 28°C and higher to travel over. Some dry air is noted to the northwest of the storm but not enough to preclude development over the next 24-36 hours as it approaches the southern shores of the island of Hispaniola. Being the case, it's a distinct possibility that Emily will be a minimal hurricane as the center either skirts the south side of the island or comes ashore on the Haitian side of the island. Interaction with the mountainous terrain of Hispaniola will disrupt Emily's development and it will likely be downgraded to a tropical storm, or even a depression, before emerging in the southern Bahamas during the afternoon hours on Thursday.

The long-range forecast for Emily becomes interesting once in Atlantic waters. Emily will be approaching the southwestern periphery of the Bermuda high and start to chart a course towards the northwest, taking the center straight through the archipelago. Environmental conditions at the end of the week appear favorable for steady strengthening, so Emily could once again be approaching hurricane strength by the time it reaches the northern Bahamas. It must be repeated that interaction with Hispaniola will have a tremendous influence in the eventual position and strength of Emily. This forecast is made with the assumption that Emily will track on the south side of the guidance envelope over the next 36 hours, limiting deterioration. Should Emily track more to the north interaction with Hispaniola will take a greater toll on the cyclone and re-intensification will be much reduced.

By this weekend Emily will be somewhere off the Southeastern US Coastline, likely regaining hurricane strength. Attention will be focused on an approaching trough of low pressure over the Great Lakes region of the country, which will begin to erode the western periphery of the Bermuda high and take Emily on a more northerly course. This path could take the center of Emily close to the Outer Banks of North Carolina and on up the East Coast to Cape Cod. Whether the cyclone as a direct impact on the Eastern Seaboard or not, tropical moisture from Emily will become entrained into the trough of low pressure approaching from the west, likely resulting in areas of heavy rain and thunderstorms this weekend from Canada to the Carolinas.



Current watches, warnings and advisories.


Eastern US current watches/warnings
Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.


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Radar: Northeast Region Loop

NE radar
Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Forecast, Tropics, Review

Updated: 1:09 AM GMT on August 03, 2011

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About sullivanweather

Thomas is an avid weather enthusiast, landscaper and organic gardener. This blog is dedicated to Northeast and tropical weather forecasting. Enjoy!

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