Northeast Weather Blog

Heavy rain and severe storms likely today

By: sullivanweather, 12:52 PM GMT on July 29, 2009

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Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.10 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued - 7/29 @8:50am

The ‘Summer Vortex’ is currently spinning just south of Hudson Bay, owning itself to the broad, deep trough carved out over much of the North American continent. Along both coasts, strong deep-layer high pressure ridges bookend this anomalous meridional flow pattern. This past week to ten days, as the trough axis retrograded west, the Northeast has been in the line of many of the disturbances rounding the base of the trough and this pattern shall continue in the near future. One strong disturbance will cross the region today and another on Friday, both bringing numerous showers and thunderstorms in the very humid airmass that will be in place over the region. As additional energy dives down the backside of the trough this weekend, heights along the East Coast will rise and surface high pressure building behind Friday’s disturbance will yield one fine day. However, the aforementioned energy will arrive Sunday and Monday bringing renewed chances for precipitation.



Near-term - Issued - 7/29 @8:50am


Across east-central upstate New York into interior New England the day has gotten off to a nice start. Other than a few pockets of dense valley fog, and a line of showers over northern Maine, partly to mostly sunny skies are gracing the early birds and with the humid airmass in place, temperatures have begun the day mild, generally in the low to mid 60’s. A few 50’s, however, are being reported across the higher terrain. Elsewhere across the Northeast skies are gray this morning and out of these gray skies it is precipitating. A few isolated heavy downpours have fired up across northeast Pennsylvania and northern New Jersey as higher theta-e air advects into this region. These isolated showers will move into southeast New York State during the morning hours and will be few and far between. Further south and west scattered to widespread showers and embedded thundershowers have advanced across the southern tier of Pennsylvania and the Upper Ohio Valley along the leading edge of the deeper moisture pushing into the region. This is evident in the precipitable water fields as they rise sharply from 1.25-1.5” north of I-80 to 1.6-1.9” south of I-80. Temperatures here have ranged from the mid 60’s across the central mountains of Pennsylvania and the Catskills of New York to the low 70’s along the coastal plain.

Short-term - Issued - 7/29 @8:50am


Deep tropical moisture will continue to surge northeastward today on the nose of a 35-40kt low level jet punching into the southern half of the region. Precipitable water contents will continue to rise as the day progresses, eventually reaching 2” across the southern tier of Pennsylvania to southern New England. Aloft there will be deep ascent as the southeastern half of the region will lie in the favorable right rear quadrant of a modest, but strengthening, 90-100kt jet streak over southern Ontario with good divergent flow over New England and strong vorticity advection provided but the advancing mid-level shortwave. These factors combined with the passage of a surface trough will ignite widespread rain and thunderstorms from late morning into the afternoon hours. This area of precipitation will move from southwest to northeast, overspreading Pennsylvania, the southern 2/3rds of New York State and southern/western New England by the evening rush. A few of the storms may become severe, with damaging wind gusts and large hail. A limiting factor for severe weather today will be the extensive cloud cover over the region this morning. While these clouds do appear thick enough to adversely affect the amount of instability this already buoyant airmass will be able to generate, CAPE values will reach 750-1500J/kg regardless. Any convection that does develop will take full advantage of the favorable environment aloft and sustain itself. Bulk shear will range from 30-35kts from eastern Pennsylvania to southern New England, priming the region for convection to organize, possibly into bowing line segments where momentum transfer will be maximized. Sufficient low-level shear/helicity also exist, being in close proximity to the developing warm front, for a possible tornado to touch down. Wet-bulb zero heights will generally range from 12-14,000’asl so hail will be limited to the stronger supercells/updrafts. Backing flow will allow for back-building and training of cells which could lead to flash flooding. As mentioned above, precipitable water contents will be around 2” so very heavy downpours may accompany some storms. High temperatures today will top out in the 70’s for most locales as cloud cover will dominate the region. Along the coastal plain south of the warm front, clouds should break and enough sun should poke through to push temperatures into the 80’s. A few 80’s may also occur over upstate New York and northern New England where the day has begun partly to mostly sunny.

The mid-level disturbance pushes through New York State during the evening hours and moves into New England during the overnight. Showers and storms will advance into the remainder of upstate New York and New England tonight as this shortwave passes through, some of these will contain very heavy rain though the severe threat should end with the loss of insolation and the belt of strongest winds moves off the coast. Basin-wide rainfall amounts should range from a quarter to half inch along the Great Lakes and St.Lawrence Valley to three quarters of an inch to an inch and a half from eastern Pennsylvania to southwestern southern New England. Localized areas where terrain enhancement or training cells set up could possibly see 3-4 inches of rain. These amounts are right at 12hr flash flood guidance values and the NWS has raised flash flood watches for these areas. Lows tonight will drop into the 60’s across the interior with 70’s along the coastal plain.

The shortwave will be moving into Canada to start the day on Thursday as the surface trough butts up against the strong Bermuda ridge offshore, becomes increasingly aligned to the low-level flow and stalls right along the coast or just offshore. Enough convergence may occur along its increasingly diffuse flanks to support some scattered showers and thunderstorms from Cape May to Cape Cod. Further west, subsidence behind the departing trough should preclude any precipitation and much of the day will be spent under mostly sunny skies. Temperatures for most areas should climb into the 80’s with 70’s confined to the higher terrain of the North Country.

High clouds will begin to advance into the Northeast out ahead of another developing trough over the Mid-Mississippi Valley region of the country which will be the next weather maker come Friday. But for Thursday night most locales will stay dry with rather mild overnight temperatures in the mid 60’s across the interior with 70’s along the coastal plain. A couple showers or thundershowers may reach the southern and western borders of Pennsylvania late in the overnight, towards daybreak as the system moving in from the southwest is a quick mover.

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Radar: Northeast Region Loop

NE radar
Fig.11 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Fig.12 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Updated: 3:56 PM GMT on July 29, 2009

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Wet pattern to return with some warmth.

By: sullivanweather, 8:00 PM GMT on July 19, 2009


**Updated with data to July 12th**

Julian Day 184

------- Extent (km^2)----Difference (km^2)
2002 – 9,984,844..…...……….-22,969
2003 – 9,835,469……..……….-60,469
2004 – 10,007,656……..……….-52,969
2005 – 9,502,813……..……….-53,906
2006 – 9,085,938……..……….-73,125
2007 – 8,925,000………………-201,875
2008 – 9,558,594………..…….-86,406
2009 – 9,507,344………..…….-112,969

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Julian Day 185

------- Extent (km^2)----Difference (km^2)
2002 – 9,890,781..…………….-94,063
2003 – 9,762,969……..……….-72,500
2004 – 9,942,500……..……….-65,156
2005 – 9,399,063……..……….-103,750
2006 – 8,965,313……..……….-120,625
2007 – 8,794,063………………-130,937
2008 – 9,434,688………..…….-123,906
2009 – 9,358,594………..…….-148,750

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Julian Day 186

------- Extent (km^2)----Difference (km^2)
2002 – 9,757,344.…...……….-133,437
2003 – 9,672,656……..……….-90,313
2004 – 9,829,531……..……….-112,969
2005 – 9,237,344……..……….-161,719
2006 – 8,774,219……..……….-191,094
2007 – 8,704,219………………-89,844
2008 – 9,309,531………..…….-125,157
2009 – 9,214,375………..…….-144,219

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Julian Day 187

------- Extent (km^2)----Difference (km^2)
2002 – 9,671,563..…………….-85,781
2003 – 9,608,750……..……….-63,906
2004 – 9,719,688……..……….-109,843
2005 – 9,109,844……..……….-127,500
2006 – 8,676,563……..……….-97,656
2007 – 8,611,094………………-93,125
2008 – 9,236,250………..…….-73,281
2009 – 9,119,219………..…….-95,156

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Julian Day 188

------- Extent (km^2)----Difference (km^2)
2002 – 9,580,000..…………….-91,563
2003 – 9,557,031……..……….-51,719
2004 – 9,671,875……..……….-47,813
2005 – 9,004,219……..……….-105,625
2006 – 8,625,781……..……….-50,782
2007 – 8,529,844………………-81,250
2008 – 9,175,000………..…….-61,250
2009 – 9,027,813………..…….-91,406

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Julian Day 189

------- Extent (km^2)----Difference (km^2)
2002 – 9,502,188..…………….-77,812
2003 – 9,490,156……..……….-66,875
2004 – 9,655,469……..……….-16,406
2005 – 8,905,469……..……….-98,750
2006 – 8,558,594……..……….-67,187
2007 – 8,455,000………………-74,844
2008 – 9,094,063………..…….-80,937
2009 – 8,951,563………..…….-76,250

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Julian Day 190

------- Extent (km^2)----Difference (km^2)
2002 – 9,454,688..…………….-47,500
2003 – 9,425,938……..……….-64,218
2004 – 9,596,406……..……….-59,063
2005 – 8,847,813……..……….-57,656
2006 – 8,456,719……..……….-101,875
2007 – 8,369,063………………-85,937
2008 – 9,045,469………..…….-48,594
2009 – 8,859,844………..…….-91,719

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Julian Day 191

------- Extent (km^2)----Difference (km^2)
2002 – 9,382,344..…………….-72,344
2003 – 9,362,500……..……….-63,438
2004 – 9,534,063……..……….-62,343
2005 – 8,768,750……..……….-79,063
2006 – 8,359,688……..……….-97,031
2007 – 8,233,906………………-135,157
2008 – 8,988,125………..…….-57,344
2009 – 8,771,250………..…….-88,594

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Julian Day 192

------- Extent (km^2)----Difference (km^2)
2002 – 9,262,344..…………….-120,000
2003 – 9,302,188……..……….-60,312
2004 – 9,458,125……..……….-75,938
2005 – 8,697,500……..……….-71,250
2006 – 8,313,594……..……….-46,094
2007 – 8,125,156………………-108,750
2008 – 8,917,969………..…….-70,159
2009 – 8,713,906………..…….-57,344

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Julian Day 193

------- Extent (km^2)----Difference (km^2)
2002 – 9,139,844..…………….-122,500
2003 – 9,234,375……..……….-67,813
2004 – 9,393,750……..……….-64,375
2005 – 8,647,031……..……….-50,469
2006 – 8,280,313……..……….-33,281
2007 – 8,015,156………………-110,000
2008 – 8,866,719………..…….-51,250
2009 – 8,687,344………..…….-26,562



(*denotes extrapolated figure)


Pics from the cryosphere



Fig.6 - Melt ponds forming on the Greenland ice cap as seen from space.



Fig.6a - Weakening shorefast ice along the Siberian coast.


Extent difference


Fig.7 - Difference in sea-ice extent between 2009 and recent years.



*Data retrieved from JAXA


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Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.10 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued - 7/19 @3:55pm

A slight change in the overall weather pattern across eastern North America is upcoming this week. The Bermuda High, which has been noticeably absent this summer, will build west and north resulting in the mean trough axis retrograding to the Mississippi Valley as the pesky upper low supporting it remains locked in place south of Hudson Bay. This will place the Northeast in deep southerly to southwesterly flow meaning a moderation of temperatures to seasonal averages in the humid airmass but also in the pathway of several moist disturbances riding up the coast. One appears to arrive Tuesday afternoon into Wednesday and the next on Friday with widely scattered afternoon convection on the days in between. By next weekend a highly anomalous pattern develops as strong deep-layer ridging builds up the Canadian Rockies, forcing yet another full-latitude trough to drop into the eastern half of the nation. The saga continues.



Near-term - Issued - 7/19 @3:55pm


A pleasant Sunday afternoon for most has materialized with the exception being northern Maine where a few thundershowers are pushing through. Otherwise skies are partly to mostly cloudy across the region with the highest concentration on clouds across the higher terrain of upstate New York and northern New England, where an isolated shower or two is possible into the early evening. East of the mountains some downsloping has cleared the skies some with a few puffy cumuli overhead. Temperatures have broken 80°F along the coastal plain in most locales with 70’s common over much of the interior, however, western New York and the higher terrain of the Adirondacks, Greens and Whites are hovering in the 60’s where the cloud cover is a bit thicker.

Short-term - Issued - 7/19 @3:55pm

There will be some clearing tonight with the loss of insolation as the atmosphere stabilizes, however, closer to the upper trough across the northern and western fringes of the region, varying levels of clouds will be present throughout the overnight. Some high clouds may begin to stream in from the south after midnight but these should be mainly confined to the coastal plain. Temperatures will drop into the 60’s along the coastal plain with 50’s across the interior. A few locations across the Adirondacks and the higher terrain of New England may find themselves in the 40’s by daybreak as well. Some patchy fog may develop across the river valleys but this shouldn’t be as prevalent as nights previous.

The building Bermuda ridge offshore begins to assert itself over the Northeast on Monday as southerly flow increases bringing more moisture to the region. The day will begin with partly to mostly cloudy skies across the far northern portions of the region, extending back along lakes to the Niagara Frontier while further south and east skies will be mostly clear to start. As the day progresses, and moisture increases, the chance for a few isolated pop-up showers or thundershowers will also increase. Hard to find much of a trigger to serve as the impetus for the development of convection other than terrain and the passage of a minor shortwave during the afternoon but that may be all it takes. Highs will be a couple degrees warmer with a moderating airmass in place, with many locations across the coastal plain and interior river valleys reaching into the 80’s. Elsewhere 70’s should do. Variable winds will begin to turn out of the south but remain light, expect along the immediate coast where 10-15mph sea-breezes will be present.

Moisture continues streaming northward Monday night as southerly flow aloft strengthens. Cloud cover will be increasing across the region as will the chances for showers and thunderstorms along the southern coastal plain as weak ripples of low pressure move up the coast from the Mid-Atlantic. Should storms develop they will be capable of heavy rainfall as precipitable water contents increase to 1.5-1.75”. Temperatures will be held up by the increase in cloud cover and humidity. Lows will only fall into the upper 60’s to low 70’s along the southern coastal plain with 60’s elsewhere along the coastal plain and much of the interior. Only far upstate New York and northern New England should drop into the 50’s for lows.



Mid-term - issued - 7/19@ 3:55pm


Model consensus is starting to come together regarding the potential for a more significant shortwave to ride up along the coast Tuesday into Wednesday, bringing a round of heavy rain and thunderstorms to the region. Tropical Maritime airmass will be pushing northwards, into the Northeast, on the deep-layer southerly flow extending to the Bahamas. This is evident in precipitable water contents rising to the 1.75-2” range east of the Appalachians into coastal New England. The track of this disturbance is still in question with some models bringing it up the Hudson Valley into western New England while others track this system more along the coast. Either way, the potential for 1-2” of rain is possible. The system will reach northern New England by Wednesday with scattered diurnal convection developing in its wake for Wednesday and Thursday. Temperatures will be close to seasonal averages or perhaps slightly above as the humid airmass keeps overnight lows elevated. High temperatures will be close to or slightly below normal thanks to varying cloud cover.


Long-term - issued - 7/19@ 3:55pm

In the long term, a highly meridional flow pattern will become established from the East Pacific to the western Atlantic. A rather remarkable ridge will build along the west coast with 500mb heights reaching into the 590dm range over southeast Alaska and northwestern British Columbia! This will cause the trough over the center of the nation to sharpen and drag down disturbances from northern Canada and direct them into the Contiguous US. Meanwhile, the Bermuda ridge off the East Coast isn’t a slouch either, having its own 590dm+ center, directly over Bermuda. Between these two massive ridges will be a deep trough centered around 90°W extending from the Canadian Arctic to the Lower Mississippi Valley. Several shortwave disturbances are expected to rotate around this trough and up the East Coast Friday into next weekend, each bringing renewed chances for showers and thunderstorms. The strongest disturbance of the bunch appears to arrive next Sunday. An early look at severe parameters shows a moderately unstable airmass, strong winds aloft with decent shear and favorable placement in the right rear quad of a 100kt or so jet streak. Temperatures will continue to remain seasonable through the weekend with a return to cooler temperatures behind the cold front to open the following week.

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Radar: Northeast Region Loop

NE radar
Fig.11 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Fig.12 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Updated: 4:16 AM GMT on July 20, 2009

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Showers and storms continue

By: sullivanweather, 1:41 PM GMT on July 08, 2009


**Updated with data to July 2nd**

Julian Day 178

------- Extent (km^2)----Difference (km^2)
2003 – 10,259,844……..……….-62,969
2004 – 10,179,531……..……….-46,719
2005 – 9,761,094……..……….-83,281
2006 – 9,526,719……..……….-58,281
2007 – 9,743,750………………-79,844
2008 – 9,992,344………..…….-62,061
2009 – 10,024,688………..…….-36,718

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Julian Day 179

------- Extent (km^2)----Difference (km^2)
2003 – 10,198,281……..……….-61,563
2004 – 10,155,156……..……….-24,375
2005 – 9,704,688……..……….-56,406
2006 – 9,435,625……..……….-91,094
2007 – 9,664,844………………-78,906
2008 – 9,949,844………..…….-42,500
2009 – 9,964,844………..…….-59,844

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Julian Day 180

------- Extent (km^2)----Difference (km^2)
2003 – 10,123,281……..……….-75,000
2004 – 10,138,125……..……….-17,031
2005 – 9,667,031……..……….-37,657
2006 – 9,366,563……..……….-69,062
2007 – 9,545,156………………-119,688
2008 – 9,870,781………..…….-79,063
2009 – 9,887,969………..…….-76,875

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Julian Day 181

------- Extent (km^2)----Difference (km^2)
2003 – 10,047,813……..……….-75,468
2004 – 10,102,656……..……….-35,469
2005 – 9,640,938……..……….-26,093
2006 – 9,314,063……..……….-52,500
2007 – 9,432,188………………-112,968
2008 – 9,783,438………..…….-87,343
2009 – 9,811,406………..…….-76,563

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Julian Day 182

------- Extent (km^2)----Difference (km^2)
2002 – 10,043,906……..……….-9999
2003 – 9,967,031……..……….-80,782
2004 – 10,092,969……..……….-9,687
2005 – 9,615,469……..……….-25,469
2006 – 9,238,594……..……….-75,469
2007 – 9,288,906………………-143,282
2008 – 9,722,656………..…….-60,782
2009 – 9,722,813………..…….-88,593

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Julian Day 183

------- Extent (km^2)----Difference (km^2)
2002 – 10,007,813.…..……….-36,093
2003 – 9,895,938……..……….-71,093
2004 – 10,060,625……..……….-32,344
2005 – 9,556,719……..……….-58,750
2006 – 9,159,063……..……….-79,531
2007 – 9,126,875………………-162,031
2008 – 9,645,000………..…….-77,656
2009 – 9,620,313………..…….-102,500


(*denotes extrapolated figure)


Sea-ice notes this week:

Weekly melt rate (6/21-28)

2009 – 56,429km^2
2008 – 62,411km^2
2007 – 79,129km^2
2006 – 87,969km^2
2005 – 68,951km^2
2004 – 56,518km^2
2003 – 57,679km^2

The melt rate for 2009 has slowed over the last week with an average rate of decline of 56,429km^2. This is likely due to the extensive cloud cover over the arctic in the western hemisphere. Near average to slightly below average temperatures is also aiding in this reduced melt rate, despite much of the ice edge consisting of first year ice.

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During the period of Julian Day 178-183 the year 2004 has an extremely slow melt rate relative to all years in the JAXA record. The 23,781km^2/day melt rate of 2004 during this period is 17,088km^2/day less than the runner-up 2005, which has a melt rate of 40,869km^2/day. Conversely, the year 2007 has a melt rate of 123,375km^2/day over the same period.

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Pics from the cryosphere



Fig.6 - Melt ponds forming on the Greenland ice cap as seen from space.



Fig.6a - Weakening shorefast ice along the Siberian coast.


Extent difference


Fig.7 - Difference in sea-ice extent between 2009 and recent years.



*Data retrieved from JAXA


___________________________________________________________



Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.10 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

--------

Forecast Discussion


Synopsis - Issued - 7/8 @9:30am


Yet another closed low descended upon the Northeast yesterday, touching off numerous rounds of showers and thunderstorms. Reports of hail were numerous and widespread with the most severe hail coming in a late-night supercell which tracked through the urban corridor of northern New Jersey and into Yonkers, New York where golf ball sized hail was reported. This intense cell also uprooted many trees and caused some minor structural damage to buildings. National weather service is being deployed to see if damage left in the wake of the storm is consistent with a tornado. Doppler radar indicated a vortex signature as this cell passed from Yonkers into New Rochelle. The severe weather wasn’t only limited to hail and high winds as Worcester, Massachusetts fell under a torrent. Three to five inches of rain fell in training thunderstorms over the city which left many roads flooded and some washed out.






This anomalous low, in any other year, has weakened markedly overnight and is beginning to fill and lift. Despite this weakening it will still serve as impetus for continued showers and thunderstorms today, albeit, not nearly as widespread or severe. High pressure builds in on Thursday and slowly translates offshore as heights build aloft. The end result will be a couple of mostly fair days and temperatures moderating back to near seasonal averages to close out the week. Another strong trough approaches this weekend and with a fairly warm and humid airmass in place, showers and thunderstorms seem like a good bet. The strong cold front plows offshore with a much cooler and drier Sunday behind it.




Near-term - Issued - 7/8 @9:35am


Satellite imagery this morning shows the upper level low pressure slowly pivoting southward into eastern Ontario with a large arc of cloud cover extending eastward away from the center, across northern New York and much of New England. Under this cloud canopy it’s damp and dreary with temperatures only in the 50’s. The greatest concentration of precipitation is over New Hampshire and Maine where several pockets of steadier, heavier showers will deposit a quarter to a half inch of rain this morning. Other lake-enhanced (believe it, or not) showers and thundershowers are moving off the southern shores of Lake Ontario into the Mohawk Valley of New York as the relatively warm lake waters are providing localized instability in this quite cool airmass. Meanwhile, much of Pennsylvania, New Jersey and southern New York are currently enjoying mostly sunny skies with patchy valley fog. Temperatures here are in the 60’s, heading into the 70’s by mid/late morning.


Short-term - Issued - 7/8 @9:35am


The showers over northern New England will continue throughout the afternoon, though they will weaken as the day progresses as the trough responsible for them becomes more diffuse. Further to the west, under the core of the cold pool aloft, showers and thunderstorms will develop as the strong July sun heats the boundary layer creating instability (CAPE values expected to be in the 400-800J/kg range). The lack of a well-defined surface feature will mean that storms will likely fire off boundaries leftover from yesterday’s convection or the terrain. A weak shortwave is also forecast to rotate through this afternoon, adding a bit of lift. However, much of the moisture has been shunted offshore, ahead of the more significant trough passage yesterday. This will lead to more scattered to isolated coverage of the precipitation. With little shear to maintain convection the storms that do develop will likely be of the pulse variety. Wet bulb zero heights are April-like, between 6-8,000asl region wide, so small hail will be present in many of the storms today and a couple large hail reports in the stronger updrafts is not out of the realm. The highest concentration of these convective showers that do develop will be across central/eastern New York and southern New England. The further south and west one heads the less the chances are for running into precipitation. In fact, much of the western two thirds of Pennsylvania will have little, if any, precipitation to speak of with mostly sunny skies under fair-weather cumulus clouds. Temperatures here will rise into the 70’s to around 80°F. Temperatures will also climb into the 70’s along the coastal plain and interior valleys. However, higher terrain and much of northern New York and New England, where clouds will be socked in, highs today should only climb into the 60’s.

Showers will continue to wane this evening as diurnal activity weakens from the loss of insolation and the upper trough shears out. Still plenty of moisture hanging around within the lingering trough axis tonight so skies will be mostly cloudy for a good chunk of real estate from eastern New York into central and southern New England. A few lingering light showers and sprinkles may dot the landscape with mist and locally dense fog developing overnight. Elsewhere across the region skies will be mostly clear as high pressure building down from Canada begins to assert itself. Under the developing subsidence inversion some locally dense fog may form in the river valleys and low lying areas, especially given how wet the ground is. Another cool July night is in store temperature-wise. Many locations will see several hours of clear skies and light winds in this rather dry airmass, allowing for optimized radiational cooling. Lows across the interior should range from the mid 40’s to low 50’s, slightly warmer under the cloud covered areas. Along the coastal plain lows will range from the upper 50’s to mid 60’s.



Mid/long-term - coming later

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Radar: Northeast Region Loop

NE radar
Fig.11 - Radar loop of the Northeast region. Courtesy of Weather Underground.


___________________________________________________________

Local SST's

Northeast SST's
Fig.12 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


___________________________________________________________



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Updated: 1:43 PM GMT on July 08, 2009

Permalink

Arctic sea-ice update

By: sullivanweather, 12:48 PM GMT on July 01, 2009


**Updated with data to July 2nd**

Julian Day 178

------- Extent (km^2)----Difference (km^2)
2003 – 10,259,844……..……….-62,969
2004 – 10,179,531……..……….-46,719
2005 – 9,761,094……..……….-83,281
2006 – 9,526,719……..……….-58,281
2007 – 9,743,750………………-79,844
2008 – 9,992,344………..…….-62,061
2009 – 10,024,688………..…….-36,718

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Julian Day 179

------- Extent (km^2)----Difference (km^2)
2003 – 10,198,281……..……….-61,563
2004 – 10,155,156……..……….-24,375
2005 – 9,704,688……..……….-56,406
2006 – 9,435,625……..……….-91,094
2007 – 9,664,844………………-78,906
2008 – 9,949,844………..…….-42,500
2009 – 9,964,844………..…….-59,844

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Julian Day 180

------- Extent (km^2)----Difference (km^2)
2003 – 10,123,281……..……….-75,000
2004 – 10,138,125……..……….-17,031
2005 – 9,667,031……..……….-37,657
2006 – 9,366,563……..……….-69,062
2007 – 9,545,156………………-119,688
2008 – 9,870,781………..…….-79,063
2009 – 9,887,969………..…….-76,875

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Julian Day 181

------- Extent (km^2)----Difference (km^2)
2003 – 10,047,813……..……….-75,468
2004 – 10,102,656……..……….-35,469
2005 – 9,640,938……..……….-26,093
2006 – 9,314,063……..……….-52,500
2007 – 9,432,188………………-112,968
2008 – 9,783,438………..…….-87,343
2009 – 9,811,406………..…….-76,563

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Julian Day 182

------- Extent (km^2)----Difference (km^2)
2002 – 10,043,906……..……….-9999
2003 – 9,967,031……..……….-80,782
2004 – 10,092,969……..……….-9,687
2005 – 9,615,469……..……….-25,469
2006 – 9,238,594……..……….-75,469
2007 – 9,288,906………………-143,282
2008 – 9,722,656………..…….-60,782
2009 – 9,722,813………..…….-88,593

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Julian Day 183

------- Extent (km^2)----Difference (km^2)
2002 – 10,007,813.…..……….-36,093
2003 – 9,895,938……..……….-71,093
2004 – 10,060,625……..……….-32,344
2005 – 9,556,719……..……….-58,750
2006 – 9,159,063……..……….-79,531
2007 – 9,126,875………………-162,031
2008 – 9,645,000………..…….-77,656
2009 – 9,620,313………..…….-102,500


(*denotes extrapolated figure)


Sea-ice notes this week:

Weekly melt rate (6/21-28)

2009 – 56,429km^2
2008 – 62,411km^2
2007 – 79,129km^2
2006 – 87,969km^2
2005 – 68,951km^2
2004 – 56,518km^2
2003 – 57,679km^2

The melt rate for 2009 has slowed over the last week with an average rate of decline of 56,429km^2. This is likely due to the extensive cloud cover over the arctic in the western hemisphere. Near average to slightly below average temperatures is also aiding in this reduced melt rate, despite much of the ice edge consisting of first year ice.

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During the period of Julian Day 178-183 the year 2004 has an extremely slow melt rate relative to all years in the JAXA record. The 23,781km^2/day melt rate of 2004 during this period is 17,088km^2/day less than the runner-up 2005, which has a melt rate of 40,869km^2/day. Conversely, the year 2007 has a melt rate of 123,375km^2/day over the same period.

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Pics from the cryosphere



Fig.6 - Melt ponds forming on the Greenland ice cap as seen from space.



Fig.6a - Weakening shorefast ice along the Siberian coast.


Extent difference


Fig.7 - Difference in sea-ice extent between 2009 and recent years.



*Data retrieved from JAXA


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Current watches, warnings and advisories.


Eastern US current watches/warnings
Fig.10 - Current watches, warning and advisories issued by the National Weather Service. Courtesy of NOAA.

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Forecast Discussion


Synopsis - Issued - 7/1 @8:45am


Deep upper level low spinning over the lower Great Lakes region will remain in place over the next 24 hours before opening as a negatively tilted trough on Thursday and lifting, finally, by Friday. Most, if not all, of the region will see some wet weather before this feature moves away but the areas from eastern New York to western New England stand the best chances for flooding rainfall. This first lobe of cut-off low pressure within a much broader overall longwave trough will be east of the region this holiday weekend with drier northwesterly flow from the Canadian Prairies and mainly fair weather with mild temperatures. Unfortunately, the second lobe of cut-off low pressure will rotate into the Northeast to begin next week with showers and thunderstorms increasing in coverage once again. This time, however, the system looks a bit more progressive and should press on into the Atlantic by the middle of next week.


Short-term - Issued - 7/1 @8:45am


The calendar may look different this morning but the view out the window sure hasn’t changed, with gray skies covering much of the Northeast. The most active weather is associated with a cluster of heavy showers and thunderstorms over southeastern southern New England and near-shore waters. Elsewhere, it’s fairly quiet. A few scattered showers are dotting the landscape over the central Pennsylvania ridge tops, along the shore of Lake Erie and across New Hampshire and Maine. Where precipitation isn’t falling the sun is scarce, aside from north of the Finger Lake region in New York. In fact, much of the area from northeast Pennsylvania to western New England has been socked in with thick fog, especially the higher terrain and river valleys. Temperatures this morning are generally in the 60’s with some 50’s confined to the normally colder inland locales and higher terrain.

With a more extensive cloud cover over the region today and weaker shortwave disturbances rotating through, shower and thunderstorm activity won’t be nearly as widespread as yesterday. Large scale ascent will still be present as the region will still lie in the favorable left exit region of an 80-90kt jet streak moving off the Mid-Atlantic Coast, the aforementioned shortwave passage and overall cyclonic flow through all levels of the atmosphere. These should all conspire to produce a blossoming area of precipitation as daytime heating becomes more of a factor by late morning. Enough sun should manage to break out to modestly destabilize the atmosphere by this afternoon, as indicated by progged CAPE values of 500-1,200J/kg, a touch lower than yesterday but more than adequate to fire convection. As for severe chances, winds aloft are lower than yesterday as is effective shear, which will only run 25-30kts. While not impressive for widespread severe weather a few stronger cells may bow into mini-line segments capable of damaging winds. Freezing levels are slightly lower than yesterday but given lower mid-level lapse rates than yesterday, storms won’t be as vertically structured. Expect cloud tops to top out in the 20-22,000’ range with VIL’s in the 30’s. Main areas for development will be across southern New Hampshire to western Maine, ahead of the weak shortwave rotating up the New England coast this morning, and across northeastern Pennsylvania to northern New Jersey, eastern New York and western New England, the areas hit hardest yesterday. This secondary area of enhanced precipitation will be due to the shortwave currently moving across central Pennsylvania. Expect the showers falling this morning to increase in coverage and intensity, eventually overspreading the aforementioned areas this afternoon. This is also the region that has been hit hardest by all the rainfall received during the month of June, so the ground is plenty saturated. Precipitable water contents are running in the 1.2-1.4” range, so the atmosphere is plenty moist. As seen yesterday given a similar set-up to today, training cells are possible and with winds aloft slightly slower, storm movement will follow suit. This combination of factors could lead to flash flooding of smaller creeks and streams, as well as poor draining and low-lying areas. Yesterday several areas saw localized 2-3” rainfall amounts and those can be replicated this afternoon. Basin wide rainfall averages should range from a quarter to half an inch so main stem rivers will simply continue running above climatology. To the west, under the core of the upper level low, activity will be more scattered, with pulse-type convection forming along weak convergence lines provided by cyclonic flow and naturally occurring boundaries around the lakes. Temperatures today will rise into the 70’s for most areas, though regions that receive early rainfall or remain socked in with low clouds and fog may hold in the 60’s. This is especially true across the higher terrain and along the immediate lake shores.

The upper level low finally begins to pivot eastwards tonight after spending a good 48 hours over Lake Huron and southern Ontario. In doing so the trough axis will begin to tilt negative and an area of low pressure will form along the coastline as a stronger shortwave rounds the base of the trough. This enhanced convergence/lift with spawn an intensifying area of showers and thundershowers along the coastal plain that will lift north-northeast as the night progresses, eventually encompassing much of New Jersey, eastern Pennsylvania, southern New England and southeastern New York. Rainfall within this band may be locally heavy, with amounts approaching and exceeding one inch. Elsewhere, much of the afternoon convection will taper with the loss of insolation during the evening hours. Any lingering showers should be located under the upper low itself over western/central Pennsylvania and across northern New England where weak shortwave energy will be passing by. Once again, fog will be a problem into the overnight across a wide swath of the region. Lows will fall back into the 60’s for most areas with a few more 50’s showing up as cooler air slowly bleeds in under the trough.

The area of low pressure slowly lifts north through eastern New York and New England during the day on Thursday with rain and thundershowers accompanying it. Cloud cover will be even more extensive tomorrow across the eastern half of the region with the significant surface low moving through, further limiting instability. So it will be rain without the thunder for most but don’t be fooled by the lack of clamoring by nature. Rain will fall quite heavy at times, leading to ponding of water and minor flash flood concerns. Further west, under the opening upper low, pop-up showers and thunderstorms due to diurnal heating will be present, but more isolated in coverage. High will once again only climb into the 60’s and 70’s.


Mid/long-term - coming later

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Radar: Northeast Region Loop

NE radar
Fig.11 - Radar loop of the Northeast region. Courtesy of Weather Underground.


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Local SST's

Northeast SST's
Fig.12 Sea-surface temperatures off the Northeast Coast. Courtesy of NOAA.


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Updated: 11:40 PM GMT on July 03, 2009

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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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