Daily Archives: Monday, June 23, 2025 9:22 am

Philadelphia Weather Outlook

THIS WEEK’S WEATHER

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Tue 4:30 PM —Forecast Review — Another hot day, where the AI models were more accurate with their temperature forecasts than the very advanced NBM statistical Model Blend. (Although the Model Blend did fine when you factor in the standard deviation.)

Here’s the RTMA temperatures at 3:45 PM—

RTMA temperatures at 3:45 PM today. Black contours are 1º increments (Click on image for a larger view.)

Here’s the official readings from the NWS Philadelphia Airport KPHL—

Highest Heat Index occurred at about 2 PM with the dew points being the highest. (Click on image for a larger view.)

Heat Continues

Posted Tuesday 06/24/25 @ 9:26 AM — Many models have similar high temperature forecast for today. The latest Model Blend (NBM) just became available. Here’s its forecast highs with degree of uncertainty (standard deviation) for today, Tuesday—

12z NBM High Temperatures (not heat index or apparent temps) (Click on image for a larger view.)

Here’s the latest ECMWF-AI model high temperature forecast—

06z ECMWF-AI High Temp forecast (Click on image for a larger view.)

Here’s the new Canadian CMC GDPS-AI forecast—

00z CMC GDPS-AI model high temps for Tuesday (Click on image for a larger view.)
Heat Recap

It really felt hot today! Temperatures seem to have only reached 99º in this area, but dew points were 70º (and where highs were only 96º, e.g. Blue Bell, the dew points were closer to 74º and 75º

Here’s the RTMA @ 3:45 PM, capturing the area’s temperatures—

RTMA 15 minute repeat model. Actual with interpolated temperatures. (Click on image for a larger view.)

The NWS has modernized their website for KPHL airport, now showing temperatures every 5 minutes—

(Click on image for a larger view.)

Of interest is the localized area of showers that developed, as predicted by the new Canadian GDPS-AI along with the wind convergence zone—

Radar at 4:35 PM Wind convergence liine with showers in southern Cape May county, as predicted by the Canadian AI. (Click on image for a larger view.)

It’s interesting that the experimental RRFS did not predict these showers in Cape May. (The NAM-NEST did predict these as well.)

For Tuesday, here’s the latest ECMWF-AI temperature forecast—

ECMWF-AI Single Temperature Forecast for Tuesday(Click on image for a larger view.)

Stay cool!

Originally Posted Mon 9:22 AM —Yesterday’s high temperatures were diminished by the unexpected and unforecast clouds and showers.

The heat will be here for sure today.

Continuing with the “experiment” from yesterday, here is the new Canadian GDPS-AI along with the Model Blend (NBM) forecast high temps for today. likely about 3-4 PM—

00z Canadian GDPS-AI high temps for Monday (Click on image for a larger view.)

Here’s the Model Blend (NBM) high temps—

06z NBM forecast high temps. Contours are 1º increments. (Click on image for a larger view.)

The “Open Data” version of the ECMWF-AI single is very similar to the above.

Just to see if the Canadian has any unique insights, it is forecasting some thundershowers to develop in NJ at 3-4 PM due to the development of a moisture convergence zone—

CMC-GDPS Moisture convergence zone thundershowers.

Stay cool!