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Tropical Storm Ophelia

Updated Fri 09/22 @ 4:39 PM — When I updated this site this morning, the storm that is forecast to affect our weekend was still referred to as Atlantic tropical depression 16. It’s been named Ophelia My regular “Weekend Weather Forecast” will cover this storm and its impact on our area.

Look for a new post shortly.

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Update Fri 9/22 8:38 AM — A quick update. No significant changes from last night’s forecast. Rain moves in from the southeast between 2AM and 4AM. Very windy with wind gusts 38-46 mph. Heavy rain on Saturday, especially Saturday late morning. Rain continues through much of Sunday. Total rainfall by Sunday evening 2-3.5”

Updates later today.

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Update Thu 9/21 9:30 PM — The latest NAEFS ( a combination of our GEFS and the Canadian ensemble models) captures the current consensus guidance for this storm—

By Sunday, 24 hours later, the surface low has filled and weakened and the upper level low lingers. It’s still raining here—

The latest NBM model just available show rainfall of 2-3” by Sunday evening and wind gusts of 35-45 mph.

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Update Thu 9/21 5:03 PM — This will a difficult forecast to get right. The model guidance is all over the map…literally. Most models now have the strong tropical low pressure moving inland. Most, but not all, have this surface low pressure system rapidly “filling” as it encounters blocking high pressure, leaving a closed upper low. Most models have about 1.5-3” of rain through Sunday, with the majority of the rain Saturday. Heaviest activity closer to the shore is a safe, but not necessarily accurate emphasis.

It’s going to be difficult to pin down specifics regarding locations of the heaviest rains and higher winds. Stay tuned

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Update Thu 9/21 8:29 AM — Last night’s ECMWF has finally joined our GFS model with a more coastal track and with the low pressure system becoming quasi-stationary as it moves over southern Delaware. The system will encounter high pressure to our north and will stall and somewhat “fill” (weaken).

High winds and heavy rains still likely with this system.

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Update Wed 9/20 9:52 PM — This afternoon’s ECMWF and NAEFS models, just available, have become a bit more similar, with the storm either moving a bit eastward, or slower just to our south. This trend would reduce the impact of the storm in our immediate area. Will have to see the trends with tonight’s models to get a better handle on this system.

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Previously Posted Wed 9:02 PM —

As mentioned over past days, a disturbance off of the Atlantic coast of Florida will develop into an intense coastal low with some tropical characteristics. It’s expected to begin to affect our area during the predawn hours of Saturday morning.

The majority of models have this system moving up the coastline, with the exception of the ECMWF, which continues to have the system bend away from the mid Atlantic coast. (Tonight’s GEFS does have the storm blocked from northward movement as it approaches the Delaware coast with a slight turn eastward. This somewhat supports the ECMWF track, but it’s too soon to hang our hats on this forecast.)

Heavy rain, high winds are likely on Saturday if it follows the track of the GFS, Canadian and German ICON models. Rainfall totals of 1.5 to 3 inches are likely, with wind gusts 35-50 mph. Impacts will be significantly less if it follows the ECMWF track.

Here’s the latest Canadian RGEM —

So, this could be a major storm for our area or it might move eastward enough to significantly reduce its impact. Stay tuned.

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This Weekend’s Storm

Updated Wed 09/20 @ 8:37 AM — The models are in good agreement (with the exception of the ECMWF) that a major Nor’easter with some tropical characteristics will affect our area beginning Friday night.

The latest GFS shows this storm at 2PM Saturday—

Anywhere from 1.5-4 inches of rain are possible with this system along with high winds and coastal effects.

The latest German ICON model shows very high rainfall possible—

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Wednesday Through Sunday Outlook

Update Tue 9/19 9:28 PM — Continued fair weather through early Friday. Increasing cloudiness expected during the day on Friday.

The models have come together forecasting a slow moving coastal storm, held back by a westward closed upper low. This is expected to move in Friday night.

The ECMWF, which had been holding back on the development of this system, has joined the other models forecasting this storm. It is a bit slower than the GFS and NAEFS, with the rain moving in during the day Saturday. Currently, it looks like it will be raining most of Saturday with somewhat light showers on Sunday.

Sometimes these storms move out faster than the model forecasts, so there’s some hope for Sunday.

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Tuesday – Friday Outlook Update

Updated Mon 09/18 @ 6:23 PM —The low pressure system off of the coast will move northeast and high pressure builds in for Tuesday through Thursday.

Fair skies and seasonably mild temperatures expected.

Clouds move in sometime on Friday.

There’s uncertainty with the low pressure development off the Florida coast. The NAEFS (combined GEFS and Canadian Global Ensemble) continues to forecast an “inverted coastal trough” moving in Friday into Saturday with clouds and an increasing chance of showers. The ECMWF is NOT currently on-board with this system moving northward. I’m leaning towards the NAEFS—

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Update Sun 9/17 11:09 PM — Tonight’s models are forecasting a slower exit of the showers Monday. We may still see some showers in Philadelphia and eastward as late as 1-2 PM.

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Previously Posted Sun 8:03 PM —

A weak coastal low will move northeast Monday. Showers may linger until 10 -11 AM and clouds will linger into the early to mid afternoon.

High pressure builds in for Tuesday through much of Friday—

Average seasonal high temperatures this week are 75º-76º. Temperatures this week will be close to slightly above seasonal averages.

So an uneventful weather week is in store for us.

Of interest is a potential tropical or semi-tropical system expected to develop off the Atlantic coast of Florida sometime on Friday. This is forecast to move north and bring clouds and rain late Friday into Saturday. Things will likely change by the time Friday rolls around.

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