REMNANTS OF ZETA TO AFFECT PHILADELPHIA AREA

A complex weather scenario involving a strong upper airclosed low”, a surface low, and the remnants of Hurricane Zeta will affect our weather from Thursday into at least early Friday.

The complexity of this setup can’t be over-emphasized and it’s likely that no existing weather model can accurately forecast how this will finally come together. Despite the complexity, the models are in relatively good agreement right now.

GFS 7 PM Thursday forecast with 1 hour rain forecast.

It appears that the upper air low and the tropical remnants will remain separate, preventing explosive development like we had with tropical storm Isaias. However, things could change and that possibility will need to be watched.

The models currently show a heavy rain event, starting Thursday morning and lasting into very early Friday morning. The CMC and GFS models have total rainfall amounts in the 2.0″ to 3.5″ range for the Philadelphia area.

As early as last Friday, the German ICON model was ahead of our GFS the Canadian models in predicting Zeta’s formation. The ICON model did very well with Isais’s precip totals. Here’s the latest ICON model cumulative precipitation forecast for the storm—

Icon Model storm total cumulative rain forecast

I expect changes in the forecast. Stay tuned.

SUNDAY FORECAST UPDATE

Note that the NBM mean temperature’s sd (standard deviation) is very large.  Be advised that several models have high temperatures only in the upper 40s!


 

An interesting weather week coming up, as a tropical system will move into the Louisiana area and merge with a strong non-tropical low pressure system in the Midwest.  This will affect us later in the week, likely Thursday into Friday.

GEFS Model Forecast Wed 11 AM (Click on image for a larger view.)