2:40 PM | Here we go again...more heavy rainfall and the threat for severe weather

Discussion

A frontal system is combining with the well-established excessively humid air mass, surface low pressure, and potent upper level support to once again raise the prospects for severe weather later today in the Mid-Atlantic region from DC-to-Philly-to-NYC and all the way eastward to the coastline. Heavy showers and embedded strong thunderstorms are currently increasing in coverage and intensity across central and western Pennsylvania and they are moving eastward into increasingly unstable air. The result will be more heavy rainfall in this region between 3 and 9PM and the likelihood of some severe thunderstorm activity to include hail, torrential rain, and damaging wind gusts. Flash flooding will once again become a serious concern later today and early tonight as grounds are super-saturated – any roadways with water should simply be avoided. The threat for showers and thunderstorms will continue well into next week with additional heavy rainfall likely, but I will say that the areal coverage of the rain is liable to be substantially diminished tomorrow with much in the way of rain-free time.

11:10 AM | Possible "derecho-caused" tsunami hit the New Jersey coast on June 13th

Discussion

The word derecho is defined as a “long-lived windstorm associated with a band of showers or thunderstorms” and it was heard for the first time by many of us during June of 2012. Well, here is another weather-related word that most have likely not heard before – meteotsunami. Meteotsunami is a rare type of tsunami that is caused by a weather event rather than from seismic activity, and it appears that one may have hit the New Jersey coast on June 13 shortly after a line of strong thunderstorms moved through the area. Those strong thunderstorms actually propagated from the Midwest to the east coast over a twelve hour period as part of a weather system that the National Weather Service subsequently labelled as a “low end” derecho, not quite as intense as the June 2012 derecho. Strong weather systems like these two derechos can cause jumps in air pressure spawning waves that act like tsunamis and it is possible that air pressure fluctuations from this month’s derecho may have caused a 6-foot wave to hit the New Jersey coast with Barnegat Light (Ocean County) bearing the brunt of the wave.

According to an eyewitness account from someone who was spear fishing near the mouth of Barnegat inlet just south of a submerged northern breakwater, the sequence of events was as follows:

Around 3:30pm on Thursday June 13, 2013, the eyewitness was spear fishing near the mouth of Barnegat Inlet; just south of the submerged northern breakwater. Earlier in the day around noon, thunderstorms had moved through the area. By 3:30pm the weather was overcast with a light east wind. At approximately 3:30, the outgoing tide was amplified by strong currents which carried divers over the submerged breakwater (normally 3-4 feet deep). This strong outrush continued for 1-2 minutes and eventually the rocks in the submerged breakwater were exposed. The eyewitness backed his boat out before being sucked over as well.

At this point, he noticed a large wave coming in, approximately 6 feet peak-to-trough and spanning across the inlet. The upper 2 feet of the wave was breaking. This wave occurred in conjunction with a reversal of the current such that even though the tide was going out, a strong surge was entering the inlet. This surge carried the divers back over the submerged reef and into the inlet from where they were picked up. On the south jetty three people were swept off the rocks which were 5 to 6 feet above sea level at the time. At least two were injured requiring medical treatment. There was no more strong activity after about 5 minutes.

Thirty tide gauges along the east coast confirmed a rise in water on that day, up to nearly a foot in spots, suggesting something indeed was going on. It could take researchers months to confirm this one way or another and other possibilities are being considered including a possible geologic disturbance such as an underwater earthquake or landslide off the continental shelf. The “slumping” at the continental shelf east of New Jersey may have played a key role.

7:00 AM | Threat for showers and thunderstorms during the mid-day and afternoon hours and the threat continues well into next week

6-Day Forecast

Today

Partly sunny, very warm, humid, showers and thunderstorms likely during the mid-day and afternoon hours, some of the rain can be heavy and any storm can reach strong-to-severe levels, highs in the upper 80’s

Tonight

Evening showers and thunderstorms likely, some of the rain can be heavy and any storm can reach strong-to-severe levels; otherwise, remaining mostly cloudy, muggy, mild, lows in the upper 60’s

Saturday

Partly sunny, very warm, humid, much rain-free time and only scattered showers and thunderstorms, upper 80’s

Saturday Night

Mostly cloudy, muggy, mild, scattered showers and thunderstorms, upper 60’s

Sunday

Mostly cloudy, warm, humid, showers and thunderstorms likely, mid 80’s

Monday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Tuesday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Wednesday

Mostly cloudy, warm, humid, showers and thunderstorms likely, mid 80’s

Discussion

More heavy rain and thunderstorms returned to the region late yesterday, but severe weather reports were generally confined to our north across central Pennsylvania. In fact, a tornado touched down late yesterday in Boalsburg - just to the east of Penn State University - and there was extensive street flooding throughout the University Park/State College region. Looking ahead, the combination of a strong upper level low pressure system anchored over the Great Lakes region and a nearly stationary extensive surface high pressure system off the east coast will keep a moist flow of air in place along the east coast for the next several days. While much of the time will be rain-free, showers and thunderstorms will remain a daily threat through at least the middle of next week and any shower can contain heavy rainfall and any storm can be strong-to-severe. Elsewhere, while the east coast remains in this very wet weather pattern, many western states will experience a major summertime heat wave. Strong upper level ridging out west will cause temperatures to soar to 100+ degrees in many of the interior locations of the Southwest US over the next few days.

Video

httpv://youtu.be/8GFeCLQRYwk

3:00 PM | **An explosive situation with heavy rain and an increasing severe weather threat**

Discussion

The combination of an intensifying and strong surface low pressure system, a well-established hot and humid air mass, and a potent upper-level disturbance is increasing the chances for severe weather for later this afternoon and evening across the I-95 corridor region from DC-to-Philly-to-NYC. Heavy showers and strong thunderstorms are already occurring from central PA to western VA and MD and this activity should affect the I-95 corridor in the period between 4 and 10PM. Torrential rainfall is likely, damaging wind gusts of up to 60 mph or so are possible, and isolated tornadoes cannot be ruled out as this explosive atmospheric scenario unfolds in the late afternoon and evening hours.

The latest mesoanalysis of severe weather indices suggest that the atmosphere is becoming very unstable in this highly populated region from DC-to-Philly-to-NYC. Wind shear profiles have strengthened a bit and the combination of moderate shear and the unstable atmospheric conditions will present a threat for damaging wind gusts, hail and heavy rainfall. Additionally, the increased wind shear profiles will likely cause enough low-level spin for the possibility of isolated tornadoes late this afternoon and evening. The threat for showers and thunderstorms will continue tomorrow, and again this weekend, and right through the middle of next week. One final note, flash flooding is a real threat this evening in any area that experiences torrential rainfall given the already well-saturated grounds.

Video

httpv://youtu.be/KshqUWGv9gk

7:00 AM | *Heavy rain and severe thunderstorm threat actually increases for later today and early tonight*

6-Day Forecast

Today

Mostly cloudy, very warm, humid, showers and thunderstorms likely, some of the rain will be heavy and any storm can be strong-to-severe, highs in the upper 80’s

Tonight

Showers and thunderstorms likely, some of the rain will be heavy and any storm can be strong-to-severe; otherwise, remaining mostly cloudy in the overnight hours, muggy, mild, lows in the low 70’s

Friday

Mostly cloudy, very warm, humid, showers and thunderstorms likely, mid-to-upper 80’s

Friday Night

Mostly cloudy, muggy, mild, showers and thunderstorms likely, near 70

Saturday

Partly sunny, warm, humid, scattered showers and thunderstorms, mid-to-upper 80’s

Sunday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Monday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Tuesday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Discussion

While the past few days have featured numerous heavy showers and strong-to-severe thunderstorms in the Mid-Atlantic region, the chances for this type of weather actually increase later today and early tonight as an upper level disturbance approaches the area. Once the upper level low reaches the eastern Great Lakes region by early Friday, it will remain rather stationary and from that location it will combine with a stationary (Bermuda) high pressure system off the east coast to continuously pump moist air into the eastern states from the Gulf of Mexico for days and days to come. Flash flooding is likely to become an increasing concern in the Mid-Atlantic region given today's expected heavy rainfall and the potential for substantially more rain over the next week or so. June has been an excessively wet month so far and we'll add significantly to that between now and the end of the month (Sunday) and then July will begin on a wet note as well. Typically, wet months at this time of year are followed by wet months which is why a common phrase among meteorologists is "wet begets wet".

Video

httpv://youtu.be/ynHwp0LR2NY

7:00 AM | *Pattern to produce multiple rounds of heavy showers and strong thunderstorms over the next 7 days*

6-Day Forecast

Today

Mostly sunny, hot, humid, scattered afternoon showers and thunderstorms, some of the rain will be heavy and any storm can be strong-to-severe, highs in the low 90’s

Tonight

Scattered evening showers and thunderstorms, some of the rain will be heavy and any storm can be strong-to-severe; otherwise, mostly cloudy skies, muggy, mild, lows in the low 70’s

Thursday

Partly sunny, very warm, humid, showers and thunderstorms likely, near 90

Thursday Night

Mostly cloudy, muggy, mild, showers and thunderstorms likely, low 70’s

Friday

Mostly cloudy, warm, humid, showers and thunderstorms likely, mid-to-upper 80’s

Saturday

Partly sunny, warm, humid, scattered showers and thunderstorms, mid-to-upper 80’s

Sunday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Monday

Mostly cloudy, warm, humid, showers and thunderstorms likely, low-to-mid 80’s

Discussion

The month of June has been very wet throughout the Mid-Atlantic region and it appears that the final days of the month, and the beginning of July, will very likely bring more substantial rainfall to the entire area. By tomorrow, we’ll start to get under the influence of an approaching unusually strong upper level low pressure trough and its associated surface cold front. The central and eastern US have had multiple unusually strong upper level troughs to deal with during the past several weeks contributing to many severe weather and heavy rainfall events. By Friday, the surface cold front will reach the east coast and strong upper level low will become established in the upper atmosphere over the Great Lakes and Northeast US. As a result of this unfolding late week weather pattern, showers and thunderstorms will become even more numerous on Thursday and Friday with heavy rainfall and severe weather almost certain to be included in the mix. That strong upper level low will then tend to spin around for a few days over the Great Lakes and Northeast US as the surface cold frontal system grinds to a halt near the coastline; consequently, the threat for showers and thunderstorms will continue on Saturday, but that won’t be the end of the wet period. In fact, surface low pressure may form along the front later in the weekend maintaining the threat for showers and thunderstorms on Sunday and Monday with additional heavy rainfall and severe weather possible. The bottom line, the next week to ten days looks quite wet in the Mid-Atlantic region and flooding may very well become a major concern given the already saturated grounds.

Video

httpv://youtu.be/AMCuuMxQRtY

9:00 PM | Heavy rain and strong thunderstorms racing across central PA should reach DC, Philly metro regions later tonight

Discussion

An area of heavy showers and strong thunderstorms is barrelling across central Pennsylvania at this hour and is headed towards the DC and Philly metro regions. This batch of rainfall is racing along at 40-45 knots and could affect these metro regions with heavy rain and potential severe weather between 10PM and 1AM. The air mass is full of moisture and any storm will be able to put down a lot of rainfall in a short period of time. The potential for heavy rainfall will continue on a daily basis right through the weekend and into next week in the Mid-Atlantic region.

11:35 AM | *Heavy rain potential for the next 7 to 10 days*

Discussion

The month of June has been very wet throughout the Mid-Atlantic region and it appears that the final days of the month, and the beginning of July, will very likely bring more substantial rainfall to the entire area - perhaps on the order of several inches. So far this month, the official rainfall totals for DC, Philly and NYC are already well above normal, and they are certain to climb substantially by the close of the month on Sunday:

6.59 inches at Reagan National Airport (3.57 inches above normal); 8.75 inches at Philly Intl Airport (6.00 inches above normal); 9.81 inches at Central Park, NY (6.17 inches above normal).

Yesterday featured scattered afternoon and evening showers and thunderstorms in the Mid-Atlantic region, some with torrential rainfall, and that same threat of heavy rain continues today and tomorrow. By Thursday, we’ll start to get under the influence of an approaching unusually strong upper level low pressure trough and its associated surface cold front. The central and eastern US have had multiple unusually strong upper level troughs to deal with during the past several weeks contributing to many severe weather and heavy rainfall events. By Friday, the surface cold front will reach the east coast and strong upper level low will become established in the upper atmosphere over the Great Lakes and Northeast US. As a result of this unfolding late week weather pattern, showers and thunderstorms will become even more numerous on Thursday and Friday with heavy rainfall and severe weather almost certain to be included in the mix. That strong upper level low will then tend to spin around for a few days over the Great Lakes and Northeast US as the surface cold frontal system remains stationary near the coastline; consequently, the threat for showers and thunderstorms will continue on Saturday as well, but that won’t be the end of the wet period. In fact, surface low pressure may form along the front later in the weekend enhancing the threat for showers and thunderstorms on Sunday and Monday with the possible outcome additional heavy rainfall and severe weather. By the way, at the same time strong upper low forms in over the Great Lakes and Northeast, an extensive and strong upper level ridge will develop over the interior western US leading to a major league heat wave for that region which will elevate the already high wildfire risks.

The bottom line, the next week to ten days look quite wet indeed in the Mid-Atlantic region and flooding may very well become a serious concern given the already saturated grounds. An even scarier scenario in terms of potential flooding for the region would be if a tropical system forms in the near future and affects the Mid-Atlantic region – not at all out of the realm of possibility as we discussed last week (Thursday, 6/20 blog).

7:00 AM | Uncomfortable heat and humidity continues with a daily shower/thunderstorm threat

6-Day Forecast

Today

Mostly sunny, hot, humid, scattered afternoon showers and thunderstorms, highs in the low 90's

Tonight

Evening scattered showers and thunderstorms; otherwise, mostly cloudy skies, muggy, mild, lows near 70 degrees

Wednesday

Mostly sunny, hot, humid, chance for showers and thunderstorms, near 90

Wednesday Night

Mostly cloudy, muggy, mild, chance for showers and thunderstorms, low 70’s

Thursday

Partly sunny, very warm, humid, showers and thunderstorms likely, near 90

Friday

Mostly cloudy, warm, humid, showers and thunderstorms likely, mid 80’s

Saturday

Partly sunny, warm, humid, showers and thunderstorms possible, mid-to-upper 80’s

Sunday

Mostly cloudy, warm, humid, showers and thunderstorms likely, mid 80’s

Discussion

Hot and humid weather will continue for the next few days with scattered afternoon and evening showers and thunderstorms. Any shower or thunderstorm that does form over the next few days can contain heavy rainfall given the current well-saturated air mass. An even more organized rain threat will arrive later in the week as a cold front approaches the east coast associated with a strong upper level low pressure system. Once that upper low reaches the Northeast US, it looks like it’ll spin around for a couple of days generating unsettled conditions around here right through the weekend with a continuing threat of showers and thunderstorms.

Video

httpv://youtu.be/uIBTj1FFBDc

7:00 AM | A pretty typical hot and humid summertime weather pattern with a threat for pop-up showers and thunderstorms

6-Day Forecast

Today

Mostly sunny, very warm, humid, chance of afternoon showers and thunderstorms, highs near 90 degrees

Tonight

Evening showers and thunderstorms possible then partly cloudy, muggy, mild, lows near 70 degrees

Tuesday

Partly sunny, very warm, humid, chance for showers and thunderstorms, near 90

Tuesday Night

Mostly cloudy, muggy, mild, chance for a shower and thunderstorm, low 70’s

Wednesday

Mostly sunny, hot, humid, chance for showers and thunderstorms, low 90's

Thursday

Partly sunny, very warm, humid, chance for showers and thunderstorms, near 90

Friday

Mostly cloudy, very warm, humid, showers and thunderstorms likely, upper 80’s

Saturday

Mostly cloudy, very warm, humid, showers and thunderstorms likely, upper 80’s

Discussion

High pressure has moved off the Northeast US coast and this has promoted a southwesterly flow of air in the low levels of the atmosphere which has transported very humid air into the Mid-Atlantic region from the Gulf of Mexico. As a result, the next few days will feature plenty of high humidity levels and the daily threat for afternoon/evening pop-up showers and thunderstorms. A more organized rain threat should come at the end of the week as a cold front approaches the east coast associated with a strong upper level low pressure trough.

One final note, I have received first-hand reports of thick concentrations of cicadas in northern Virginia, northern New Jersey and upstate New York, but Pennsylvania reports appear to be conspicuously absent.

Video

httpv://youtu.be/EznAzuQy11k