Thursday 8:05 PM Update — The latest models continue to push the start of the rain later in the day on Sunday, now late afternoon.
The weekend is looking much better, as the circulation of Hurricane Delta will fall apart as it moves into an upper air ridge environment on the East coast.
Here’s the [latest available on public web] Navy COAMPS model forecast for Hurricane Delta—
The trend has been for the rain to move in later on Sunday.
Saturday will see high cloudiness move in in advance of the tropical moisture
The models have pretty much lined up with yesterday’s Model Blend, having the precipitation wait until Sunday afternoon for the Philadelphia area.The NBM (Model Blend) has light rain starting in the mid afternoon, but several models hold it off until late Sunday afternoon.
Here’s the latest Model Blend (NBM) precip forecast for 3 PM Sunday—
Rain slowly increases in intensity during the late afternoon and evening. Heaviest rain on expected on Monday.
This will be plain rain event, especially late Sunday through Monday. About 1-1.5 inches of rain is expected by late Monday afternoon. Nothing like Isais.
Not surprising, the timing of Hurricane Delta’s impact on the Philadelphia area has changed somewhat over the past 24 hours and there’s uncertainty regarding the timing of the rain here over the weekend.
While the latest [publicly available} COAMPS model maintains a similar track and a somewhat faster movement, the track of the remnant moisture towards our region is somewhat delayed back into the Sunday time frame.
The latest GEFS (Global Ensemble Forecast System) has the rain reaching our area 11 PM Saturday night—
The new GEFS forecast represents the statistical average of 30 versions, called “members”, of 30 separate GFS model runs.
The 30 members and a ‘control version’ are collectively called the “ensemble”.
Each member has an introduced ‘perturbation’, a known, mathematically introduced error to account for the uncertainty in measurement of initial weather conditions.
The latest blend of models (NBM) delays the rain into Sunday afternoon, although there’s a chance of light sprinkles earlier and increasing cloudiness will arrive as early as Saturday—
I expect more changes in this forecast, as hurricanes and tropical storms seem to adversely affect model forecasts. Stay tuned.