#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.
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.
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.
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.
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.
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.
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.
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.
So if I’m understanding you correctly, another shot at tropical rainfall will miss us, yet again, for–yet again–high pressure blocking?
That would be incredible. The pattern has to break at some point, but gadzooks my plants would appreciate it sooner rather than later….
Yes, that’s what it looks like. Often, tropical systems break up a persistent pattern. No sign of that yet. If the storm lingers longer in the Gulf, we may see any opportunity for a western track. But not currently supported.