Marine Weather Net

Delaware Bay south of East Point NJ to Slaughter Beach DE Marine Forecast


REST OF TODAY

W
WINDS
10
KNOTS

TONIGHT

W
WINDS
5 - 10
KNOTS

THU

NW
WINDS
5 KNOTS

THU NIGHT

SW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ431 Forecast Issued: 1002 AM EDT Wed Sep 23 2020

Rest Of Today...W Winds Around 10 Kt. Waves Around 3 Ft.
Tonight...W Winds 5 To 10 Kt. Waves Around 3 Ft In The Evening, Then 2 Ft Or Less.
Thu...Nw Winds Around 5 Kt, Becoming S Around 5 Kt In The Afternoon. Waves 2 Ft Or Less.
Thu Night...Sw Winds 5 To 10 Kt. Waves 2 Ft Or Less.
Fri...S Winds 5 To 10 Kt. Waves 2 Ft Or Less.
Fri Night...S Winds 5 To 10 Kt. Waves 2 Ft Or Less. A Chance Of Showers.
Sat...S Winds 5 To 10 Kt. Waves 2 Ft Or Less. A Chance Of Showers.
Sat Night...S Winds Around 10 Kt. Waves 2 Ft Or Less.
Sun...Sw Winds Around 10 Kt. Waves 2 Ft Or Less.
Sun Night...Sw Winds 10 To 15 Kt. Waves 2 Ft Or Less. A Chance Of Showers.
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Area Forecast Discussion
National Weather Service Mount Holly NJ
855am EDT Wednesday September 23 2020

Synopsis
High pressure will remain near the Ohio and Tennessee Valleys through today as Post-Tropical Cyclone Teddy moves through portions of Atlantic Canada. High pressure then slowly drifts off the southeast coast later this week into this coming weekend. A cold front looks to move through from west to east sometime late Sunday or Monday.

Near Term - Through Tonight
845 AM...Mid level vort max passing off the coast and in its wake an expansive area of high pressure centered near the Midwest will dominate our weather. With this surface high to our southwest and Teddy to the northeast, another day of breezy west/northwest winds is expected. Speeds will increase to around 10 to 15 mph this afternoon with occasional gusts to 20 mph or so. This may produce sufficient mixing to counter the increasing dew points somewhat, and we also did lower the dew points for today slightly with the mid morning update. Nevertheless, still expect dew points will be higher than yesterday resulting in a lower fire-weather risk.

With increased midlevel ridging upstream of Teddy, expect warmer temperatures today, with highs likely to be a few degrees above seasonal averages. Based on a statistical blend of guidance, maximum temperatures are forecast to be in the 70s to around 80.

A couple of weak northwest-flow perturbations will move through the Northeast tonight, which will shunt the surface trough offshore and will promote a period of dry advection and decreasing surface dew points. This will likely allow for temperatures to fall appreciably during the overnight hours, at least while skies remain fairly clear. This is most likely to occur in the northern CWA, where forecast lows are in the mid 40s to lower 50s. Farther south, warmer temperatures are expected, as upper-level lift begins to increase in advance of a southern-stream vort max associated with (ejecting from) the remnants of Beta approaching the southern Mid-Atlantic. Cloud cover may increase late, curbing a more precipitous fall in temperatures. Confidence is lower in this area, as the timing of the increased cloud cover is unclear. For now, increased lows about 2-5 degrees near/southeast of the urban corridor, generally in line with the warmer statistical guidance.

One other thing: A translucent layer of smoke exists aloft early this morning but is expected to shift southeast out of the region today. Impacts to sensible weather will likely be low or negligible, though it may have an influence on the colors seen during sunrise.

Short Term - Thursday Through Friday Night
The main challenge for the short-term forecast period is the evolution of the remnants of Beta across the southern and eastern U.S.

A complex upper pattern will start the period (12z Thursday), as a large-scale trough with an embedded and potent vort max will be in place across Ontario/Quebec, a southern-stream trough associated with the remnants of Beta will generally be positioned near the Mississippi Valley, and a kicker northern- stream perturbation will dig southeastward into the northern Plains. Downstream flow will become quasi-zonal, with the long- duration surface high across the eastern U.S. finally beginning to shift offshore.

The surface high will continue to influence our region, so another dry day with winds becoming more southwesterly should be expected for our area. However, cloud cover will likely be increasing associated with a midlevel speed maximum downstream of the southern-stream trough. As a result, current forecast retains slightly warmer-than-average temperatures for our area on Thursday. Thursday night lows will also be warmer (likely around 3 to 8 degrees above seasonal averages), as southerly surface flow aids in warm/moist advection in advance of the southern-stream shortwave trough.

Models are really struggling with the ultimate track of Beta's remnants, with the 00z ECMWF (European Centre for Medium-Range Weather Forecasts) much farther north than the 00z GFS/CMC. The sensitivity lies with the digging northern-stream vort max and the large-scale trough in eastern Canada. The CMC produces the least amplification downstream of the kicker shortwave trough, leading to a track well south of the area (aided by fairly strong amplification of the eastern Canada trough). The GFS depicts more interaction between the two perturbations and a slightly farther north track. The ECMWF allows for more complete phasing of the perturbations, resulting in a lift northward of Beta's remnants sufficient for precipitation to move into southern portions of the CWA by Friday afternoon. The NAM is farther north than the GFS but weakens the system substantially by the time it reaches the coast. There are noticeable timing discrepancies as well, with the CMC considerably slower than other guidance.

The GFS/CMC solutions would result in dry weather for our area, but the ECMWF leads to a fairly wet Friday and Friday night for areas south of the I-76 corridor. Given the large disparity in model guidance, decided to include some slight-chance Probability of Precipitation for Friday afternoon and Friday night for the southern half or so of the area. The odds still appear to be higher that most or all of the area remains dry, but this will bear watching.

Temperatures on Friday and Friday night will obviously depend on coverage of clouds/precipitation, so went with a consensus blend for now. This results in forecast values near seasonal averages.

Long Term - Saturday Through Tuesday
The medium-range forecast looks fairly active, as the pattern transitions to a western-ridge/eastern-trough configuration by early next week. As large-scale trough amplification occurs Sunday and Monday in vicinity of the Midwest/Great Lakes, a series of surface cyclones will develop with attendant cold fronts. The timing/strength of these fronts is the primary forecast challenge for our region.

Saturday's forecast remains muddled owing to the track of Beta's remnants, but currently expect chances for Probability of Precipitation to be fairly low by Saturday afternoon and night. Highs and lows should be near to slightly above average.

In general, the synoptic evolution from Sunday through Tuesday looks fairly straightforward. The first potent vort max will dig into the Great Lakes on Sunday before lifting northeastward via downstream ridge amplification on Monday. A surface low will strengthen in advance of the trough in vicinity of the Saint Lawrence Valley Sunday and Sunday night, with a cold front forecast to move through the Northeast by Monday. Generally have chance Probability of Precipitation for the area Sunday afternoon through Monday, and have also included a slight chance of thunderstorms owing to a pronounced improvement in low-to-midlevel lapse rates via strong synoptic ascent in advance of the trough. However, coverage and timing of precipitation remain unclear, given some pronounced differences among the deterministic models. The ECMWF may be on the slow side, given its tendency to amplify these systems too much.

A brief dry period is likely before the second and stronger system digs into the Great Lakes on Tuesday. Rapid cyclogenesis will occur in this vicinity, with a strong cold front likely to approach the region by Tuesday night or Wednesday as the large- scale trough acquires a neutral to slightly negative tilt. This system will bring our first chance of rather widespread convection with potential for decent Quantitative Precipitation Forecast in a long while to the area. After a period of lower Probability of Precipitation Monday night and Tuesday morning, increased probabilities return Tuesday afternoon onward.

Temperatures Sunday through Tuesday will be near to slightly above seasonal averages.

Marine
For the Atlantic waters, seas of 6 to 9 feet will continue early this morning, diminishing quickly to 4 to 6 feet this afternoon. Seas should subside below advisory criteria by this evening. Northwest to west winds 10 to 20 kt with occasional gusts to 25 kt early this morning should trend downward today and tonight as well. A small craft advisory remains in effect through 8 pm. Sub-advisory conditions are expected tonight.

For Delaware Bay, sub-advisory conditions are expected through tonight. There may be a brief period of stronger winds (15 to 20 kt or so) early this morning as some channeling occurs.

Outlook... Thursday through Sunday...Sub-advisory winds/seas expected. Periodic chances for showers Friday through Sunday.

Rip currents... A high risk of rip currents remains on the Atlantic beaches of New Jersey and Delaware today, as a very long-period swell is expected to continue. With seas subsiding, we expect the rip- current risk will lower to the moderate category on Thursday.

Tides / Coastal Flooding
Models have generally been forecasting tidal levels too low the past several hours. Surge has increased from Teddy churning well northeast of the area, and models suggest the surge will peak later this morning. High tide is during the early afternoon, and it is the higher of the two daily cycles. ETSS and Stevens Institute ensemble data support widespread minor flooding on the Atlantic coast during the high tide today.

As a result, we have issued a coastal flood advisory from 12 to 6 pm for the Atlantic coast, including associated back bays and the southern shore of Raritan Bay.

For Delaware Bay and the tidal Delaware River, confidence is lower in tidal levels reaching advisory thresholds. However, some guidance is quite aggressive in generating a surge up into the tidal Delaware River this afternoon. For now, think this is overdone, but we will be watching observations closely this morning to determine if the more aggressive solutions are on to something.

NOAA Mount Holly NJ Office: Watches - Warnings - Advisories
PA...None. NJ...High Rip Current Risk through this evening for NJZ014-024>026. Coastal Flood Advisory from noon today to 6pm EDT this evening for NJZ012>014-020-022>027. DE...High Rip Current Risk through this evening for DEZ004. Coastal Flood Advisory from noon today to 6pm EDT this evening for DEZ003-004. MD...None.
MARINE...
Small Craft Advisory until 8pm EDT this evening for ANZ450>455.