7:15 Am

Summer-like conditions will return to the forecast area and will do so in a short period of time.  That means that humid air and temperatures in the 80′s and possibly 90′s will return to the forecast area.  When the hot summer conditions return, I’m willing to bet that the conditions will feel hotter and more humid just because many have been subjected to such a cool, wet weather pattern the past several weeks.  However, before we get to the warm conditions, we’ll have to deal with the low pressure that is stalled to the east of the region. 

The low pressure system over the western Atlantic is still rather strong and has a large range of influence, which extends into the forecast area.  Locations further west like over eastern Pennsylvania will be under less of an influence from this low pressure system will only have to contend with partly cloudy skies and an isolated shower.  However, closer to the coast, especially over Connecticut, eastern Long Island, and the immediate New Jersey coast; the low pressure system will have a stronger influence over the region.  The cyclonic rotation will bring disturbances and moisture from the Atlantic into the coast, which will produce scattered showers and isolated thunderstorms, especially in the afternoon.  The low pressure system will continue to influence the region over the next three days, but to less of a degree each day.  The north to northwesterly wind over the next several days, will produce a down sloping wind component, which will allow temperatures to warm into the 80′s.  

Note the red colors over the Mississippi Valley.  This is an indication of a developing ridge that will eventually build into the Ohio Valley by Wednesday afternoon.  This ridge will continue to build towards the Mid Atlantic through the end of the week, which will bring much warmer conditions to the forecast area.  The ridge axis will be west of the forecast area, over the Great Lakes, which means a northwesterly upper level flow will allow cold fronts to still clip the forecast area with a risk of showers and thunderstorms.  The first of these cold fronts will move through on Friday afternoon and once again on Sunday afternoon.  

So has the wet pattern completely left the forecast area?  Well, not exactly.  What has happened is that the pattern will not be as amplified, which means the trough over eastern Canada will lift northward.  As a result, a pattern that resembles and produces warmer summer conditions will develop.

6:40 AM

An area of low pressure over the Atlantic Ocean remains stalled and will continue to influence conditions over the coastal waters today.  Partly cloudy skies can be expected with a risk of widely scattered showers, especially in the late afternoon hours.  The showers and thunderstorms will be capable of brief heavy downpours and strong wind gusts.  However, most thunderstorms will remain below severe levels.  Tonight, partly cloudy conditions will continue with a few isolated lingering showers.  On Tuesday and Wednesday, weak disturbances will continue to rotate around the low pressure system over the Atlantic, bringing a risk of scattered showers each afternoon.  Otherwise, partly cloudy skies can be expected through the period.

Winds will be from the north around 10 to 20 mph through tonight.  Locations east of Long Island will have sustained winds from the north around 20 to 40 mph with higher gusts, prompting a gale warning. On Tuesday, winds will remain from the north, but will decrease to 5 to 15 mph.  On Tuesday night and Wednesday, winds will back slightly to the northwest around 5 to 15 mph.  

Temperatures will rise into the lower to mid 70′s for highs this afternoon.  On Tuesday, temperatures will fall into the upper 50′s to lower 60′s for morning lows and rebound into the lower to mid 70′s for afternoon highs.  On Wednesday, temperatures will fall into the lower 60′s for morning lows and rebound into the upper 70′s for afternoon highs.  

Water temperatures will range from the mid 60’s to lower 70’s over the New Jersey coastal waters down through the Delaware Bay.  Much cooler waters are expected east of Long Island with water temperatures in the upper 50’s to mid 60’s. 

Wave heights will range from 3 to 6 feet through this evening.  Waves will subside overnight to 2 to 4 feet and remain in that range through the rest of the forecast period.  

A small craft advisory is in effect through this evening.  A coastal flood watch is also in effect through tonight for the New Jersey coast.

9:52 AM

June has seen some very impressive rainfall amounts with many locations well over an inch above normal.  Even some locations double the amount of normal rainfall.  While a continuous onslaught of showers and thunderstorms have impacted much of the Mid Atlantic, and specifically the New York City and Philadelphia metropolitan areas, other locations have been impacted with an above normal outbreaks of severe weather, especially tornado outbreaks from the southern Plains through the Mississippi Valley and Ohio Valley.  

Before going into the why, I want to show the rainfall anomalies throughout the region.

Connecticut:

Bridgeport, CT: +2.19″      Danbury, CT: +1.76″       Norwich, CT: +1.05″

New York:

Islip, NY:  +2.24″                New York City, NY:  +4.06″         JFK, NY:  +3.27″       LGA, NY:  +3.02″

White Plains, NY:  +1.05″

New Jersey:  

Atlantic City, NJ: +3.77″    Cape May, NJ: +1.90″          Freehold, NJ: +0.67″      Hightstown, NJ:  +1.31″

Millville, NJ: +1.74″      New Brunswick, NJ: +1.31″     Sussex, NJ:  +2.69″     Newark, NJ: +2.69″

Pennsylvania:

Allentown,PA: +2.23″      Philadelphia, PA: +1.28″    Lehighton, PA: +2.52″  

First, I want to address some of the differences seen in the magnitude of the above normal anomalies.  Some locations area barely a half an inch above normal while other locations are 3 to 4 inches above normal.  There is no trend in the precipitation anomalies that would support a synoptic or large scale pattern explanation, so I examined the radar trends over the past month and noted that the majority of the rainfall amounts were produced by convective precipitation events.  In other words, the extreme precipitation anomalies that did develop were supported by thunderstorms that happened to intensify over those locations.  The overall theme for the most part is that most locations ranged 1.5″ to 2.5″ above normal for June, and there is still 9 days left in the month with plenty of rainfall potential.  

So what is causing all of this rainfall?

To answer this question, I looked at two key factors that can drive a weather pattern, the stratospheric temperature anomalies and the Pacific sea surface temperature anomalies.  

El Nino: 

This summer, a weak El Nino has developed over the Pacific Ocean.  El Nino is when air pressure pattern in the South Pacific orient themselves where pressure is higher over Darwin, Australia is higher than at Tahiti which leads to a decrease in strength of the trade winds.  As a result, the water along South America is allowed to pile up, which inhibits up welling and allows the waters to warm.  The warming of the Pacific waters produces an atmospheric environment where the jet stream over North America is further south and more energized than normal.  The stronger the El Nino event, the further south and more energetic the jet stream.  

As we can see with the map to the left, El Nino is well on the way of developing and is certainly in a weak state of El Nino.  As a result, the jet stream over much of the United States is amplified and further south.  The position of the jet stream will certainly support the reason why the weather pattern has been so active.  A jet stream position further south would certainly support an environment where severe weather potential would be high.  Disturbances are able to have more interaction with the moist, warm Gulf of Mexico air mass, which can lead to wide spread severe weather out breaks.  However, the El Nino event alone would not explain why cold fronts have stalled over the forecast area, which has produced the heavy rainfall.  

Stratospheric Temperature Anomalies and the Negative NAO:

The key to understanding the cause of the wet pattern over the Mid Atlantic is to look at the interaction between the developing El Nino and the position of stratospheric temperature anomalies.  The stratospheric temperature anomalies have produced an environment the past twenty days that has produced a negative NAO and negative AO pattern.  The negative NAO pattern is key here as the higher pressures at 500 MB over northeast Canada and Greenland produces a blocking environment over North America.  As a result, instead of troughs simply lifting through the Northeast, the upper troughs and upper lows tend to stall over the Eastern Great Lakes.  As the upper lows and troughs begin to stall over the Great Lakes, the cold fronts drive towards the East coast, but lose support by the time they reach the forecast area.  

Meanwhile the combination of the strong jet stream over the Mississippi Valley and the stalled trough over the Great Lakes has enhanced a ridge over the southern Mississippi Valley and Gulf Coast.  This ridge over the Gulf of Mexico adds the ingredients of deep mid level moisture from the Gulf of Mexico and prevents cold front from moving much further south than the southern Mid Atlantic in most cases.  

Overview:

The combination of the developing El Nino and the negative NAO patterns have lead to heavy rainfall that has been recorded over the forecast area.  The El Nino produced an energized jet stream that is much further south than normal, which leads to strong disturbances to move through the Mississippi Valley and then the Great Lakes.  The negative NAO pattern, which is supported by stratospheric temperature anomalies, has produced high latitude blocking.  The high latitude blocking has kept a trough over the Great Lakes in place rather than lift out, which means that disturbances around the trough continue to rotate through the Mid Atlantic and Northeast.  Meanwhile, the interaction between the El Nino enhanced jet stream and negative NAO pattern has produced a strong ridge along the Gulf Coast.  

The ridge along the Gulf Coast is forcing moisture through the Ohio Valley and into the Mid Atlantic.  The cold fronts, with weakening upper level support, stall up against the ridge.  The moisture, as a result, is lifted along the cold fronts and thus the constant threat for showers and thunderstorms for days and weeks on end.  

10:00 AM

The visible satellite picture this morning shows us that once again, yet another weekend has been spoiled by wet, soggy conditions.  However, I do have some good news for this afternoon.  Note that over the Hudson Valley and over eastern Pennsylvania that the clouds have started to break up and some clouds are lifting over New Jersey.  Also, the latest radar images show many of the showers that have moved through the forecast area this morning are weakening.  

The low pressure system off the East coast this morning will continue to have a strong influence over the forecast area through the next several days.  This morning the low pressure system will have the strongest influence on the forecast area, which has produce widely scattered showers and periods of steady rain.  However, as the low pressure system weakens over the Atlantic and a ridge builds over the Ohio Valley, much drier air will continue to work into the forecast area from New England and eastern Canada.  

Through this afternoon, expect showers to continue to weaken and continue to become widely scattered.  In fact, this process has already started over the Hudson Valley and much of Connecticut.  Further south, the showers are slightly more intense over the New Jersey coast, however the showers will also weaken here by the afternoon.  In fact, some sun shine may even break through some high and mid level clouds through the afternoon.  

Tonight through Tuesday, a northerly wind will continue to impact the forecast area as high pressure to the west and low pressure to the east will remain in place through the period.  Variable cloud cover will remain over the forecast area through the period with low clouds and fog a constant theme along the immediate coast.  Widely scattered to isolated showers will also remain a threat each afternoon and evening as disturbances rotating around the upper low over the Atlantic.  

On Wednesday and Thursday, the upper low and trough east of the forecast area will weaken and lift northeast, which will lead to much drier and warmer conditions.  High pressure will build into the forecast area on both days with winds remaining light and variable.  Temperatures will be the warmest than what has been experienced so far this summer.  In fact, there is even a slight chance for temperatures to approach 90 degrees over the Delaware River Valley on Thursday.

The warm pattern will be very short lived though.  The trough will reestablish itself over the Great Lakes once again.  This means that weak, slow moving cold fronts will once again impact the forecast area.  The first two cold front on Friday and Saturday will be very weak and only produce widely scattered to isolated showers.  However, going forward, the return of the very wet pattern that has plagued the month so far will return for the end of the month through early July at least.

9:23 AM

Low pressure east of Long Island and south of New England has stalled and will impact the forecast area over the next several days.  Variable cloud cover can be expect today through Tuesday.  Scattered showers will be rotating through the coastal waters through this afternoon as the low pressure system slowly drifts east.  Showers will become widely scattered tonight and tomorrow as the low pressure system loses influence.  Variable clouds and isolated showers can be expected on Tuesday.

Winds will be from the north and northwest around 10 to 20 mph today through this evening.  Tonight through Monday, winds will remain from the north and northwest around 15 to 30 mph.  Winds will decrease from the north on Monday night through Tuesday around 5 to 15 mph.  

Temperatures will rise into the mid 60′s to lower 70′s for afternoon highs.  On Monday, temperatures will fall into the upper 50′s to lower 60′s for morning lows and rebound into the upper 60′s to lower 70′s for afternoon highs.  On Tuesday, temperatures will fall into the upper 50′s to lower 60′s for lows and rebound into the lower to mid 70′s for afternoon highs.  

Water temperatures will range from the mid 60′s to lower 70′s over the New Jersey coastal waters down through the Delaware Bay.  Much cooler waters are expected east of Long Island with water temperatures in the upper 50′s to mid 60′s.

Wave heights will range from 2 to 4 feet through the period.  A small craft advisory is in effect through early Tuesday morning for much of the coastal waters due to the low pressure system off the coast.  

Minor coastal flooding may be an issue for the northern shores of Long Island and the south facing bays throughout the forecast area due to the persistent northerly winds over the next several days.