WEEKEND WEATHER FORECAST

Previous coverage of Ian can be found here.

Updated Sun 10/02 11:12 PM —Tonight’s early models are showing the remnants of Ida have become a closed upper low that will meander near our area through late Tuesday. Monday may see a reduction of the rain from Philadelphia and westward, but rain rotates back in on Tuesday.  The ECMWF is showing several inches of rain possible in some areas on Tuesday.
I’ll be updating this interesting setup tomorrow

Update Sun 10/02 @ 8:42 AM — Fascinating convergence zone has developed over us—

Radar at 7 AM shows area of converging winds (Click on image for a larger view.)

The diagram on the HRRR forecast for 8:30 AM—

06z HRRR forecast for 8:30 AM shows surface winds. I’ve added the notations of the direction of the upper air winds Also visible is the wavy light orange “500-1000 thickness line” showing a small scale ‘wave‘ over our area. This convergence and wave are causing the rain. This feature is forecast to move slowly eastward over much of Philadelphia for the afternoon. (Click on image for a larger view.)

Unfortunately, the Eagles game looks like it will be played in the rain (and wind.)


Updated Sat 10/01 10:41 PM — Tonight’s models are now forecasting that even Sunday morning will have some light drizzle or rain. Rain increases in coverage and intensity during the afternoon. It looks like a wet day at the Linc.


Update Sat 10/01 @ 4:07 PM — Today’s models suggest a dry period before noontime on Sunday, but additional rain will fill in between noon and 2 PM as upper disturbances rotate in around the upper low. The HRDPS captures this —


Forecast Review— We had the break in the rain mid to late morning, but the HRRR was overly optimistic forecasting breaks in the clouds.

Read More

Sunday

The upper low in West Virginia will throw more clouds and rain towards us, so much of the same.

Several models that were showing a break in the rain Sunday afternoon have moved away from that forecast this afternoon. The NAM-NEST still shows relatively little rain in the city at 3 PM. The NBM shows more widespread on and off light rain in the afternoon.

NAM-Nest forecast for 3 PM Sunday (clouds- black) rain a1 hour accumulated (green contours) and simulated radar. (Click on image for a larger view.)

High temperature 58.4º sd 3.0º NBM model, Blue Bell, PA

THIS WEEK’S WEATHER

Hurricane Ian has its own web page. Click here.

Update Fri 09/30 @ 8:55 AM —Updated the Tropical Storm Ian page with weekend outlook and change in timing and amount of rain.

Update Tue 09/27 @ 6:08 PM — (Updated Hurricane Ian page) We continue to be a northerly flow of dry air through Friday. We may begin to see some high clouds associated with Ian Friday.


The latest ECMWF shows some rain for us by Saturday afternoon from Ian.

Latest ECMWF forecast for Saturday at 2 PM. Rain moves in from Ian. (Click on image for a larger view.)

Previously Posted Mon 9:32 PM —

Our weather this week will be influenced by an upper air trough bringing continued cooler, temperatures. Current seasonal average highs are 70-72º. We’ll be seeing upper 60s over the next two days.

Water Vapor image shows jet stream level winds and the position of upper level systems. The trough over the eastern part of the country will combine with a southerly flow over the Carolinas and Georgia to influence the movement of Hurricane Ian. (Click on image for a larger view.)

This corresponds to the current depiction of the NAEFS

NAEFS current conditions Monday evening (Click on image for a larger view.)

The remnants of Hurricane Ian will affect us later in the week and more likely, during the weekend. I’ll be following the models.

Current indications, based on the GFS, ECMWF and ICON models, suggest that the bulk of the rain associated with this storm will move just to our south late Saturday into Sunday. With hurricanes, anything can happen and changes are likely. Stay tuned



WEEKEND WEATHER FORECAST

Updated Sun 9/25 11:02 PM — Monday looks mostly sunny and windy. A few instability showers may move through during the afternoon hours. 

Tropical storm Ian looks like a forecasting challenge, with several models keeping a track close to the western coast of Florida and some maintaining an eastern turn into north central Florida.  Weakening still forecast if it moves northward as it encounters large high pressure. Some models have the storm slowing as it encounters this high. 

Stay tuned.


Update Sun 09/25 @ 5:38 PM — The rain came in pretty much on schedule, about 2-3 PM. Some areas, with thundershowers, had a bit more rain than had been predicted.

CAPE values weren’t all that high but there was enough vertical shear to create a few storms. Frankly, I was a little surprised by that. That said, I had no idea why they were predicting possible severe storms.

Here’s the total rainfall based on the MRMS—

MRMS rainfall this afternoon (Click on image for a larger view.)

As for Tropical storm Ian, uncertainty exists whether it will turn eastward into western Florida or whether it will move more northward into the Gulf coast. Most models still have it sheared off as it moves northward into strong high pressure, so as it approaches the Gulf coast, it may weaken.

Unless it moves more westward, much of the moisture with Ian will likely move off to our south before getting here at the end of the week or weekend. Stay tuned.


Updated Sat 9/24 9:56 PM — Tonight’s models have the showers moving into Philadelphia between 1-3 PM, earlier to our west. Precipitation will be light, about 0.1-0.2 inches of rain.

Regarding the new tropical storm/hurricane Ian, it appears that it’s headed for Louisiana, not Florida. Many models show it being sheared apart and weakened as it plows into strong high pressure.


Updated Sat 9/24 12:32 PM — A quick mobile update. This morning’s models have leaned toward an earlier onset of the showers on Sunday. Most likely 1-3 PM. The showers no longer stop at our doorstep until evening.


A cold front moved through Thursday and today, Friday, and it was noticeably colder than its been for a long time!

Current water vapor satellite image shows current jet stream level features—

Water Vapor at 6 PM with superimposed radar and RAP model jet stream wind flow. Upper low pressure will cause a surface low to develop and move over us later Sunday. (Click on image for a larger view.)

For Saturday — An interesting looking weather map for 2 PM Saturday, as high pressure builds in over us and an impressive, strong hurricane Fiona moves into Nova Scotia and Prince Edward Islands.

NAEFS forecast for Saturday at 2 PM. Impressive hurricane Fiona to our northeast. (Click on image for a larger view.)

For Sunday, the low pressure system near Wisconsin will move towards us with a warm front late Saturday and some showers late Sunday. Incredibly, the models show most of the rain to our west, skipping over Philadelphia, and redeveloping to our east.

Saturday

Some cloudiness mid-morning as an upper air disturbance moves through, then mostly sunny. Winds much lighter.

High temperature 60.3º sd 1.2º NBM model Blue Bell, PA

Sunday

Increasing cloudiness in the morning. Cloudy by noontime. The latest GFS has showers moving into western suburbs early afternoon (2PM) but not advancing into Philadelphia until the evening. The heaviest rain looks like it skips over Philadelphia. Increasingly windy and gusty!

High temperature 75.0º sd 2.0º NBM model Blue Bell, PA