1:15 PM | ***Significant rainfall for the Mid-Atlantic region and a hurricane threat late in the weekend***

[Visible satellite image of Hurricane Joaquin with signs of an "eye" forming; courtesy Penn State/Weather World]

Discussion

A potentially dangerous weather pattern is unfolding for the Mid-Atlantic region that can include very heavy rainfall, flooding and beach erosion along coastal sections over the next few days from the combination of strong “blocking” high pressure to the north and a “nor’easter-like” storm system. In addition, there is the potential for major impacts from Hurricane Joaquin in the Mid-Atlantic region late in the weekend or early next week. Exactly where Hurricane Joaquin makes landfall – if ever – is still in question with some of the most recent model information suggesting North Carolina and others sticking with an "out to sea" solution. However, whether or not Joaquin actually makes landfall in the US, significant rainfall is still likely to occur and NOAA's GFS forecast model continues to predict 5-10 inch amounts in much of the Mid-Atlantic region over the next seven days (shown below).

[12Z GFS total rainfall output for the next 7 days (orange area is 5-10 inches; courtesy NOAA]

Hurricane Joaquin has strengthened slightly in the past few hours with sustained winds now at 80 mph. Joaquin has moved slowly to the southwest during the past several hours, but the shortwave ridge causing this motion will weaken in a day or two as a strong upper-level trough forms over the Southeast US. Once this upper-level trough becomes well-established, the hurricane is likely to turn northward and then “pin wheeling” action around the upper-level low could cause Joaquin to push to the northwest – perhaps right towards the Mid-Atlantic coastline.

[Shear tendency during the past 24 hours; courtesy University of Wisconsin/CIMSS]

As far as intensification is concerned, Joaquin is moving into a region with little or no wind shear (circled area on map above) and over warmer-than-normal waters - all of this should allow further strengthening – perhaps even to category 3 (“major hurricane”) status. Joaquin is likely to reach its lowest pressure in about 72 hours or so and then begin to weaken slowly as it pulls farther up the coast on its way over somewhat cooler waters. Strong “blocking” high pressure will set up later this week across southeastern Canada and this will be a key player in the eventual possible push of Joaquin towards the Mid-Atlantic coastline and also in its slow movement throughout the next several days.

One of the reasons for concern in this unfolding pattern is that there will be a “nor’easter-like” event ahead of a potential strike by Joaquin. Heavy rain and a long-lasting period of strong onshore flow (20-40 mph E-NE winds) will take place in the Thursday-Saturday time period and this would make any potential rainfall from Joaquin late in the weekend or early next week that much more damaging.

Bottom line…all eyes from North Carolina to Long Island should continue to closely monitor this unfolding situation.

7:00 AM | ***Significant rainfall for the Mid-Atlantic region and a weekend hurricane threat***

6-Day NYC Forecast

Today

Mostly cloudy, muggy, an occasional shower likely, highs in the mid 70's

Tonight

Mostly cloudy, cooler, showers likely, lows in the low-to-mid 50’s

Thursday

Cloudy, breezy, quite cool, periods of rain likely, near 60 degrees

Thursday Night

Cloudy, breezy, cool, periods of rain possible, near 50 degrees

Friday

Cloudy, windy, cool, rain likely, upper 50's

Saturday

Cloudy, windy, cool, periods of rain likely, potentially hurricane-like conditions depending on the track of Joaquin, mid 60’s

Sunday

Cloudy, windy, cool, periods of rain likely, potentially hurricane-like conditions depending on the track of Joaquin, mid 60’s

Monday

Cloudy, windy, cool, periods of rain likely, potentially hurricane-like conditions depending on the track of Joaquin, mid 60’s

Discussion

Tropical Storm Joaquin was in an environment yesterday that featured some vertical wind shear which kept a lid on intensification, but that wind shear relaxed somewhat overnight and strengthening has now brought Joaquin to hurricane status (category 1) with 75 mph winds. It is entirely possible that Hurricane Joaquin reaches category 2 or 3 levels over the next couple of days as it churns over the western Atlantic Ocean in a favorable environment. Quite a serious and complicated weather pattern is unfolding for the Mid-Atlantic region with many players on the field and it could all result in very significant rainfall between tomorrow and the end of the weekend and - given the real threat of a hurricane strike - there is the possibility for damaging winds, power outages and beach erosion in coastal areas.

A strong cold front is slowly pushing through the region at this time and it will soon stall out along the east coast. This frontal system generated some heavy rainfall in the Mid-Atlantic region, but that is likely just the opening event. Low pressure now situated over the northeastern Gulf of Mexico is then likely to ride up along the stalled out frontal boundary zone generating additional significant rainfall later in the work week. Then, as deep upper-level low sets up in the Southeast US, Hurricane Joaquin is likely to "pin wheel" towards the northwest on a track that could bring it to the Mid-Atlantic coastline over the weekend. All eyes from New Jersey to Virginia should closely monitor this situation. Computer forecast models are not universal in a Mid-Atlantic strike...there is still a scenario that keeps Joaquin out to sea although significant rainfall would still occur in the region. Stay tuned.

Video

httpv://youtu.be/kKRN3c5aszA

1:00 PM | **Very significant rainfall with a tropical connection continues to threaten the Mid-Atlantic region for later this week and weekend**

[Latest visible satellite image of Tropical Storm Joaquin; courtesy Penn State eWall]

Discussion

Quite a complicated weather pattern is unfolding for the Mid-Atlantic region with many players on the field and there are reasons for concern that it could all result in some very significant rainfall later this week and into the weekend. First, a strong cold front will slowly push through the region at mid-week and then will stall along the east coast. This frontal passage will generate some heavy rainfall in the Mid-Atlantic region from later tonight into Wednesday, but that is likely just the opening salvo. Low pressure now situated over the northeastern Gulf of Mexico is then likely to ride up along the stalled out frontal boundary zone generating additional significant rainfall later in the work week. Finally, the combination of a strong upper-level low in the Southeast US late this week and Tropical Storm Joaquin now spinning east of the Bahamas could bring more significant rainfall to the Mid-Atlantic region this weekend.

Tropical Storm Joaquin continues to churn at this hour in the waters east of the Bahamas with sustained winds at 35 knots. The development of the upper-level low later this week over the Southeast US has been consistently forecasted by the computer forecast models with Joaquin “pin wheeling” around it back towards the Mid-Atlantic coastline (“pin wheeling” is known in the meteorological community as the “Fugiwara” effect). Joaquin is currently in an area of wind shear which should suppress intensification somewhat in the near term, but once the shear weakens in 48 hours or so, it could very well strengthen into a hurricane later this week - perhaps even a category 2 or 3. One final note about Joaquin...it may or may not ever make a direct hit on the Mid-Atlantic coastline, but even if it does not, it could still have a major impact by supplying tremendous amounts of tropical moisture into the region.

Two other important factors in this unfolding weather event include strong and very slow-moving high pressure which will be situated across southeastern Canada at the end of the week and sea surface temperatures that are above-normal throughout the western Atlantic. Strong and very slow-moving high pressure across southeastern Canada at this time of year often results in tropical mischief along the US east coast. Above-normal sea surface temperatures in the western Atlantic (orange area in the map below) can only help with the intensification prospects for Tropical Storm Joaquin as tropical systems are fueled by warm waters.

[Sea surface temperature anomalies in the western Atlantic; map courtesy "tropicaltidbits.com"]

Bottom line…our dry weather pattern of recent weeks will end in a dramatic fashion over the next several days. Very significant rainfall - on the order of 5 to 10 inches according to the latest GFS model run (below) - is on the table for the Mid-Atlantic region in the time period from later today through the upcoming weekend.

[12Z GFS total rainfall forecast over the next 6 days; courtesy NOAA]

Stay tuned.

Paul Dorian Vencore, Inc.

7:00 AM | *Heavy rain threat tonight and tomorrow as cold front pushes through the region...tropical threat at end of week and/or this weekend*

6-Day NYC Forecast

Today

Mostly cloudy, still rather warm and muggy, showers likely later this afternoon, possibly a thunderstorm, highs near 80 degrees

Tonight

Mostly cloudy, muggy, mild, occasional showers and possibly a thunderstorm, some of the rain can be heavy, lows in the upper 60’s

Wednesday

Periods of rain, maybe a thunderstorm or two, some of the rain can be heavy, cooler, near 70 degrees

Wednesday Night

Mostly cloudy, cool, showers likely, breezy, mid 50’s

Thursday

Mostly cloudy, breezy, cool, showers possible, near 60 degrees

Friday

Mostly cloudy, breezy, cool, rain possible and it could be significant, low 60’s

Saturday

Mostly cloudy, breezy, cool, rain possible and it could be significant, low-to-mid 60’s

Sunday

Mostly cloudy, breezy, cool, rain possible and it could be significant, low-to-mid 60’s

Discussion

The overall weather pattern in recent days has generally been without significant rainfall, but heavy rain is a possibility on a couple of occasions during the next several days. A strong cold front will push some rain into the area later today, tonight and on Wednesday and some of that rain can be heavy at times. A few thunderstorms can also mix into the picture over the next 24 hours or so as the cold front slowly pushes through the region.

This frontal system will then stall out near the coastline and its boundary zone will act as a conduit for moisture to ride along later in the week and plenty of moisture will be available. In fact, a tropical depression near the Bahamas yesterday strengthened overnight into Tropical Storm Joaquin and there is a reasonable forecast scenario that brings this system back towards the Mid-Atlantic coastline at the end of the week and/or during the upcoming weekend. This type of track would certainly raise the prospects for more heavy rain and potential strong winds in at least coastal sections of the Mid-Atlantic. Stay tuned.

Video

httpv://youtu.be/xNXM4nZHbZA

3:00 PM | *Tropical connection is a late week/weekend concern*

[12Z Euro model forecast for Saturday morning; courtesy tropicaltidbits.com]

Discussion

Our relatively dry weather pattern in the Mid-Atlantic region is coming to an end this week and there is some reason to be concerned about a potential heavy rain threat at the end of the week or over the weekend that could have a tropical connection. A strong cold front will push through the region on Wednesday generating heavy rain in the area along with possible thunderstorms. This front will stall out near the coastline and low pressure is likely to ride along the frontal boundary zone. There is a currently a tropical depression (#11) sitting well off the Southeast US coastline and it may get wrapped into this unfolding pattern. In fact, the latest Euro model (above) suggests the tropical system could strengthen later this week and then push back towards the Mid-Atlantic coastline (ala Sandy) over the weekend with heavy rain in its path. The key to this Euro model scenario is its forecast of a strong upper-level low in the Southeast US at the end of the week which "captures" the surface low pressure system and pulls it back towards the coast. Another model – NOAA's HWRF – which is specifically designed for hurricane forecasting has the track farther north than the 12Z Euro ultimately pushing the system into northern New Jersey (below) or thereabouts. Strong high pressure across southeastern Canada later this week does certainly allow for the possibility of a tropical system to “back in” towards the east coast, but the movement of the strengthening upper-level low is a difficult part of the forecast. Stay tuned.

[Storm track of tropical system by NOAA HWRF model (in purple); courtesy NOAA]

7:00 AM | Strong cold front brings rain to the region tomorrow night into Wednesday - some of it heavy and maybe a thunderstorm - then much cooler air follows...more rain possible at week's end

6-Day NYC Forecast

Today

Mostly cloudy, muggy, warm, patchy fog early, a little light rain possible at times, highs near 80 degrees

Tonight

Mostly cloudy, muggy, mild, chance for a couple of showers, lows in the upper 60’s

Tuesday

Mainly cloudy, still muggy and warm, a few showers likely, near 80 degrees

Tuesday Night

Mostly cloudy, mild, showers likely, maybe a thunderstorm, some of the rain can be heavy, mid 60’s

Wednesday

Mostly cloudy and not as warm, periods of rain, maybe a thunderstorm, some of the rain can be heavy, low 70’s

Thursday

Mostly cloudy, breezy, cooler, chance for showers, mid 60’s

Friday

Mostly cloudy, cool, chance for rain, low-to-mid 60’s

Saturday

Mostly cloudy, cool, chance for rain, low-to-mid 60’s

Discussion

A strong cold front will push through the region on Wednesday and it’ll likely generate some heavy rain later Tuesday into Wednesday before a fall-like air mass follows for the latter part of the week. The front will stall near the coastline and this will allow low pressure areas to ride along the boundary zone at the end of the week perhaps bringing more substantial rainfall to the I-95 corridor.

7:00 AM | Onshore flow of air continues this weekend with an increasing chance of showers

6-Day NYC Forecast

Today

Partly sunny, breezy, cool, highs in the low 70’s

Tonight

Partly cloudy, breezy, cool, lows in the upper 50’s

Saturday

Partly sunny, breezy, cool, low 70’s

Saturday Night

Mostly cloudy, breezy, cool, upper 50’s

Sunday

Mainly cloudy, breezy, cool, chance for showers late; showers likely at night, low 70’s

Monday

Mostly cloudy, breezy, cool, showers likely, mid-to-upper 70’s

Tuesday

Mainly sunny, warmer, near 80 degrees

Wednesday

Mainly sunny, pleasant, upper 70’s

Discussion

Strong high pressure from Canada is building southeastward and will combine with low pressure off the Mid Atlantic coastline to continue to produce an onshore flow of air into our area. The low pressure system will push slowly northwestward over the next couple of days and the result will be an increasing chance for showers around here later this weekend and the shower threat is likely to linger into Monday as well. Coastal locations could experience above-normal high tides, rip currents and even some beach erosion over the weekend given the expected long-lasting onshore flow of air and these effects will be exacerbated by the full “supermoon” which takes place on Sunday.

Video

httpv://youtu.be/AfHeoI4xatM

7:00 AM | Onshore flow this weekend with an increasing chance for showers

6-Day NYC Forecast

Today

Mainly sunny, warmer, highs in the upper 70’s

Tonight

Partly cloudy, cool, lows near 60 degrees

Friday

Mainly sunny, breezy, cooler, low-to-mid 70’s

Friday Night

Partly cloudy, cool, upper 50’s

Saturday

Partly sunny, breezy, cool, chance for showers at night, low 70’s

Sunday

Mainly cloudy, breezy, cool, chance for showers, low 70’s

Monday

Mainly cloudy, cool, chance for showers, mid-to-upper 70’s

Tuesday

Mainly sunny, pleasant, upper 70’s

Discussion

Strong high pressure from Canada will build southeastward over the next 24 hours and this will combine with low pressure off the Mid Atlantic coast to continue a persistent onshore flow of air into our area. The low pressure system will push slowly northwestward over the next few days and the result will be an increasing chance for showers around here this weekend. Coastal locations could experience above-normal high tides, rip currents and even some beach erosion over the weekend given the expected long-lasting onshore flow of air and these effects will be exacerbated by the full “supermoon” which takes place on Sunday.

7:00 AM | Nice weather for today and Thursday

6-Day NYC Forecast

Today

Mainly sunny, warmer, highs rebound to the upper 70’s after a cool start

Tonight

Mainly clear, cool, lows in the low 60’s

Thursday

Mainly sunny, nice, upper 70’s

Thursday Night

Partly cloudy, cool, near 60 degrees

Friday

Partly sunny, breezy, cool, low-to-mid 70’s

Saturday

Partly sunny, breezy, cool, chance for showers late or at night, low-to-mid 70’s

Sunday

Mainly cloudy, cool, chance for showers, low-to-mid 70’s

Monday

Partly sunny, cool, mid 70’s

Discussion

High pressure will build back into the region for today and Thursday and the resultant increase in sunshine will boost afternoon temperatures each day to noticeably warmer levels compared to the past couple of days. Low pressure off the Carolina coastline will push northward at a snail's pace at the end of this week and weekend and it will combine with strong high pressure to the north to generate a persistent onshore flow of air. Showers are possible during the weekend in the Mid-Atlantic region; especially, in areas south and east of Route I-95. Coastal sections could see some above-normal high tides, rip currents and even beach erosion over the weekend given the expected persistent onshore flow of air and all of these conditions will be exacerbated by the full "supermoon" on Sunday.

Video

httpv://youtu.be/JmIW3cFGDgE

2:45 PM | Persistent onshore flow, full “supermoon”, and potential coastal low pose problems this weekend/early next week for at least parts of the Mid-Atlantic region

[12Z GFS forecast map for Monday morning; courtesy NOAA]

Discussion

High pressure will reassert itself in the Mid-Atlantic region during the next couple of days and sunshine should return in full force which will help boost afternoon temperatures to noticeably warmer levels. At the same time, abundant moisture will continue to reside just off the east coast. This area of moisture will push northward at a snail’s pace over the next few days at the same time strong high pressure slides to our north. Eventually, a significant rain event could very well occur in at least parts of the Mid-Atlantic region. The possible timing for this rain event is in the Sunday/Monday time period, but a quicker arrival of the moisture cannot be ruled out. The 12Z GFS forecast map above for Monday morning shows an area of precipitation (greens, yellows) in the southern part of the Mid-Atlantic region and there is an impressively strong flow of moist ocean air right into the area.

[Current "wind flow" map shows large fetch over the Atlantic Ocean; courtesy earth.nullschool.net]

Whether this significant rain event ever materializes, this persistent ocean flow of air will likely to lead to heavy surf, rip currents and beach erosion along coastal sections by the weekend. The wind flow map above shows a long fetch of onshore flow already in place along the Mid-Atlantic coastline (courtesy earth.nullschool.net). All of these coastal effects will be made worse this weekend by higher-than-normal tides as the moon will reach full “supermoon” status on Sunday. A “supermoon” occurs 6 times this year and is defined as when the new or full moon comes within 224,834 miles of Earth as measured from the centers of the moon and Earth. A full “supermoon” is 12 to 14 percent brighter than a full moon in its most distant approach to Earth. Stay tuned...especially along coastal locations.