Monthly Archives: October 2024

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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#Philadelphia #weather #PAwx #drought

Philly Drought Watch

Posted Friday 10/25/24 @ 11:28 AM — Our next chance of any rain appears to be the first few days of November. Unfortunately, the latest AI and ensemble models show an upper air ridge in our area that may seriously reduce the amount of rainfall we get ahead of a cold front.

Here’s the ECMWF-AIFS forecast for November 2

ECMWF-AIFS (Artificial Intelligence Model) forecast for 8 PM Saturday Nov 2nd. Light showers ahead of a cold front, dissipating as they move eastward. (Click on image for a larger view.)

Here’s the GFS AI model forecast for Sunday Nov 3rd—

GFS Graphcast AI Machine Learning Model forecast for Sunday Nov 3 at 7 PM. Again, upper ridge will reduce our rainfall potential. (Click on image for a larger view.)

On the more positive side is the NAEFS (ensemble model combined GEFS and Canadian ensemble). It’s forecasting more rain and possible coastal tropical system near Florida. Likely not correct—

NAEFS forecast for Wednesday Nov 6th . Tropical system hinted at near Florida coasts. (Click on image for a larger view.)
The Drought Continues

Posted Thursday 10/24/24 @ 5:01 PM — I can’t remember the last time I saw so many large sprawling high-pressure systems on the weather map. Our dry weather is expected to continue into the first few days of November.

Until that time, we’ll have some colder periods towards the end of this weekend as a second cold front moves through early Saturday. We’ll see another warm-up next week. And mostly sunny skies shall prevail.

I may have to rename this blog, “The Rain Watch”. I’m currently using various statistical ensemble models and the ECMWF-AI and GFS-AI models to see about our next chance of rain

We may finally get some rain, albeit, hardly a drought-buster, sometime in the November 3rd through November 5th time frame.

Here’s the ECMWF-AIFS forecast for November 3—

ECMWF-AIFS forecast for 7 AM November 3. A cold front moves through with about a quarter inch of rain, possibly more if low pressure develops along the front. (Click on image for a larger view.)

Posted Tuesday 10/22/24 @ 4:27 PM — As mentioned yesterday, two cold fronts will move through in the coming days; one late Wednesday night into Thursday and another late Friday night into Saturday.

These frontal passages have been forecast to be dry, but today’s ECMWF and Canadian RGEM show a deeper trough moving through with enough lift for with some sprinkles, mainly in NJ late Wednesday night. The few sprinkles forecast are supported by the experimental REFS. (The ECMWF-AIFS shows no showers.)

We’re only talking a one or two hundredths of an inch in a few locations.

During the weekend, our current well above average temperatures will drop to noticeably cooler levels.

The GraphCast AI-Machine Learning version of the GFS has moved the chance of rain here further down the road into November from yesterday’s forecast. So the drought continues.

10-22-24 00z Graphcast-GFS forecast for Monday, November 4th. Our first chance of light rain?? (Click on image for a larger view.)
No Rain

It’s been a long time since things seemed so dry outside. And the current extended range forecasts keep thing dry for us over the next two weeks!

Yes, there will be two cold fronts moving through this week. The first one will result in a familiar pattern of having any rain shear off to the far north and west of the city—

Today’s ECMWF shows showers only far north of the city. (Click on image for a larger view.)

Another cold front moves through Saturday. The models had been forecasting some light showers for us, but those have all but disappeared in the forecast—

Today’s GFS forecast for Saturday. Grey black is cloud cover. Essentially no rain with this front. (Click on image for a larger view.)

I’m still playing with the highly experimental AI-Machine Learning version of the GFS. It still seems to show the first chance of any substantial rain here is November 3rd!

Graphcast GFS (AI Machine Learning model ) forecast for November 3rd. (Click on image for a larger view.)

All I can say is “Wow”.

Philadelphia Area Weather Forecasts

WEEKEND WEATHER FORECAST

#Philadelphia #weather #PAwx

There’s almost no reason for a weather forecast for this weekend and certainly not a reason for many updates. You’ve heard the details on the radio or TV.

Sprawling dominant high pressure and a persistent upper air ridge will give us sunny skies and increasingly warm temperatures. I don’t see any rain here in the Philadelphia area until the end of October, possibly on Halloween, according to the NAEFS and into November according to the GFS AI model.

During this downtime, I’ve been exploring programming downloads and post processing of some the the experimental AI models.

Regular readers here have seen that the ECMWF-AIFS was quite impressive with its forecast of Helene and Milton.

NOAA also has what they call an experimental “machine learning model” which is a combined effort with Google (Graphcast) and uses the weather database of the ECMWF. It compares current conditions to a weather database going back to the late 70s with several parameters at 13 vertical atmospheric levels to create a forecast.

Over the past week or so, I’ve been working on programming the download and post processing of what’s called the Experimental Graphcast-GFS model. (Weather model downloads are much more complex than simply “click here” for the model.)

Here’s its forecast for October 31st at 8 AM, showing the first area of rain on the map for awhile. Notice that the rain is blocked to our west by high pressure.

10-18-24 00z Experimental Graphcast GFS for Halloween morning. High pressure still blocking rainfall. But it suggests a pattern change within several days of this date. (Click on image for a larger view.)