#Philadelphia #weather #PAwx

Folks, I’m recovering today from a routine surgical procedure today, Friday. I hope to be back online tomorrow.

Friday through Sunday

Posted Thursday 10/03/24 @ 3:25 PM — Some cloudiness expected Friday morning, then sunny mid-day. Clouds move in again during the afternoon ahead of a cold front.

The showers associated with the cold front pass through Saturday morning, before daybreak. Most areas will see little in the way of rainfall. Currently the RRFS shows some rain, mostly in Chester county, but that may change.

A mostly sunny weekend expected. Another front moves through late Sunday night into Monday morning with a somewhat greater chance of some rain here.

Regarding the tropical system in the Gulf of Mexico, the models are all showing it to remain weak, possibly only a tropical storm, with central pressures of about 1000mb (Helene was in the 955mb range. Average sea level pressure is 1013.8 mb) . Plenty of rainfall is expected in central Florida with this system and there will likely be a problem with flooding, as rain is expected for several days.

Despite the consistent ECMWF-AIFS forecast shown several times earlier this week, most models have a weak system with two or more centers. One of these centers will move across Florida and eastward while the other center might hang back, again blocked by high pressure to the north.

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Thursday through Saturday

Posted Wednesday 10/02/24 @ 5:18 PM — High pressure builds in for Thursday and Friday. Mostly sunny skies Thursday and Friday morning. Clouds move in Friday afternoon ahead of a cold front. This cold front will move through Friday night into Saturday morning with the possibility of light showers Saturday morning, especially areas northwest of the city.

The deterministic and ensemble models are still not convinced of a hurricane in the Gulf. Some tropical system will bring heavy rain into Florida is currently all that’s forecast.

The artificial intelligence/machine learning model of the ECMWF continues to have a hurricane develop by Monday afternoon—

Notice that blocking high pressure (blue shading above) will force any storm to an easterly track. The above also shows some showers early Monday for our area as another cold front moves through.

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Wednesday Update

Posted Wednesday 10/02/24 @ 9:14 AM — Last night’s models have backed off on the showers reaching Philadelphia today. It now appears that they won’t make it into the western suburbs of Chester/Montco/Bucks either.

Regarding the potential storm in the Gulf of Mexico, the ECMWF-AIFS and the German ICON model continue to forecast a hurricane to develop around the Sunday time frame, while the statistical ensemble models show multiple low pressure centers and less distinct development. The ECMWF is leaning towards development and the GFS somewhat less so. The Canadian Global shows hurricane development but northward movement from the Gulf is blocked by high pressure in the US.

For illustration purposes, the statistical (ensemble) version of the ICON, the ICON-EPS, captures the uncertainty of several other models—

So still quite a range of forecasts.

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Gulf Tropical Storm Update

Posted Tuesday, 10/01/24 @ 8:10 PM— Just a brief update. Today’s later models are increasingly forecasting another tropical storm or hurricane to develop in the same area as Helene with a current likely track taking it into northern Florida. Time frame varies as early as Sunday or early next week. The AI version of the ECMWF did surprisingly well with Helene and it shows much more defined development than previous runs.

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Wednesday’s Weakening Cold Front

Posted Tuesday 10/01/24 @ 4:02 PM —As expected, the rain stayed to our west and south today. A cold front approaches on Wednesday, but this front falls apart as it approaches Philadelphia.

Most models show some shower activity in the afternoon (2 PM-4 PM) with the rainfall tapering off as it approaches Philadelphia.

The experimental REFS is the most impressive regarding our western sections receiving rainfall—

It looks like Chester, and to some extent Delaware county, will receive the most rainfall. Other models keep the ‘heavier’ rain west in Lancaster county with even lighter totals closer to the city.

As for the next tropical storm in the Gulf, the models continue to show limited development and intensification. The low pressure system may linger in the Gulf longer. It’s definitely a different scenario than Helene so far.

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Tuesday Forecast Update

Posted Monday 09/30/24 @ 6:11 PM — High pressure to our northeast is forecast to block any rain from getting close to Philadelphia and its immediate suburbs on Tuesday. While the ECMWF and Canadian RGEM have some showers near Philadelphia, I’m going with the high resolution models along with the latest GFS which keep Philadelphia and most of the surrounding areas cloudy but dry.

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Monday Update

Posted Monday 09/30/24 @ 10:13 AM — We had some bright spots and even some sun about 8 AM, but the latest models have backed off on the sunny breaks this afternoon, keeping any clearing further north and eastward—

The latest NAM-NEST is still optimistic about some sun here this afternoon, but not the latest HRRR.

So, I’m leaning towards continued cloudy conditions, but we may be pleasantly surprised regarding a few bright skies and sun, especially north and east of the city.

Our “rainfall” on Tuesday has been reduced to perhaps a few isolated spits at most. Our relatively dry pattern continues.

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Originally Posted Sun @ 5:33 PM — —This coming week’s weather will be a gradual improvement in conditions. with several systems to affect us.

Monday– High pressure builds in from the northeast, allowing partial clearing in the afternoon and maybe some sun, especially north of the city.

Here’s the REFS (experimental) cloud cover for Monday at 2 PM—

Tuesday– Remnants of Helene and upper low induce a surface low off the coast of Virginia. Blocking high pressure in the northeast will significantly reduce any rainfall in the immediate Philadelphia area. We’ll probably just see clouds and any light rain will fall in southern Chester and Delaware counties and Cape May County NJ.

Here’s the NBM (model blend) rainfall forecast for Tuesday—

Wednesday– Cold front moves through with most of the rain and dynamics moving off to the north of our area.

High pressure and another cold front moves in sometime Thursday into Friday.

The models are forecasting another tropical system in the Gulf for next weekend, but vertical wind shear may reduce degree of intensification.

Today’s models are forecasting a less impressive storm, but that could change. Too early to know.

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#Philadelphia #weather #PAwx

Past 72 Hour Rainfall Totals

Posted Sunday 09/29/24 @ 10:31 AM — Through 9 AM Sunday, the MRMS rainfall totals for the previous 72 hours—

Not much additional rain expected through Tuesday, except in areas shown below.

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Sunday Update – Week Forecast Outlook

Posted Sunday 09/29/24 @ 9:55 AM — Humid tropical air in our area overrunning high pressure to our northeast will continue to bring low level clouds, mist and the chance of light drizzle or light rain today, Sunday. Total rainfall looks to be less than Saturday. Northeast wind flow will keep us near 70º.

A break in the action with even some sun possible during the afternoon Monday, especially areas Philadelphia and northeastward, as high pressure builds down.

Low pressure developing along the Virginia coastline had been expected to bring us a decent rainfall Tuesday, but there’s been a consistent trend towards this low being too far to our south, suppressed by blocking high pressure. So very little rain now expected for Tuesday—

A cold front moves through Wednesday. Little additional rainfall here.

Incredibly, the extended range models are strongly hinting at another tropical storm or hurricane in the Gulf next weekend, with a track similar to Helene. The machine learning/AI model ECMWF-AIFS has also been consistently showing a storm forming by next Saturday—

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Continued Cloudy with Varying Light Showers

Posted Saturday 09/28/24 @ 10:12 AM — Last nights 06z models and this morning’s 12z models continue to forecast low clouds and intermittent light showers through Saturday. Some models show some thinning of clouds in southern Delaware and Chester counties towards evening, but that reverses itself overnight.

There isn’t much change for Sunday according to the RRFS and REFS experimental models.

Here’s the current setup Saturday morning with light showers from very moist southeasterly flow—

While some models continue with a more substantial rainfall for Tuesday, the GFS is suggesting a further southeasterly development of low pressure which would have the heavier rain miss us. Too soon to tell.

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Total Rainfall So Far

Posted Friday 09/27/24 @ 5:44 PM — We need the rain. How much rain have we gotten over the recent days? Here’s the MRMS totals through 4 PM today.

Quite a range of values over our region!

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Originally Posted Fri @ 5:01 PM — —The remnants of Hurricane Helene continue to rotate into and merge with an upper air low over Tennessee.

Considerable moisture is being flung up towards Philadelphia from the south and southeast around this combined system and as it hits a high pressure ridge just northeast of us, the moisture is riding up over it and condensing out as rain.

By Sunday afternoon, the upper low will have remained almost stationary, but will begin to move eastward and perhaps induce a surface low off the coast for Tuesday—

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