Category Archives: Tropical Storm Outlooks

Tropical Storm Outlooks

Tropical Storm Ophelia

#weather #philadelphia #phillyweather

Sunday Forecast Update

Updated Sun 09/24 @ 5:20 PM — The main area of rain is exiting our area, but continued light drizzle and showers are still forecast through the night.

Radar at 4:48 PM Sunday with superimposed RAP model jet level windstreams (orange) and moisture convergence (blue)

The NBM has the [heavy] rain exiting in time for the Phillies game at 6 PM—

Today’s 18z NBM simulated radar (colorized contours) and cloud ceiling at 6 PM. (Click on image for a larger view.)
Sunday Forecast Update

Updated Sun 09/24 @ 11:40 AM — Rain will continue through this afternoon and tonight. There may be some periods where the rain lets up, but expect it to return.

It looks like the mastodon wxcloud.social server is offline

Current water vapor image with superimposed RAP model parameters shows an area of vorticity and instability approaching. Showers and even some thunderstorm activity is possible this afternoon —

Current WV and RAP potential vorticity and MUCAPE (Click on image for a larger view.)

The latest HREF model shows considerable additional rainfall for our area for the next 24 hours—

This morning’s 12z HREF forecast for additional accumulated rainfall 8AM Sunday through 8 AM Monday. (Click on image for a larger view.)

Latest MRMS (10AM) total estimated rainfall over this weekend so far—

Sunday Forecast Update

Updated Sat 09/23 @ 9:46 PM — This afternoon’s and this evening’s early models have periods of rain continuing through the night and much of Sunday into Monday morning!

There may be a break in the showers in some areas around 9 AM Sunday, but showers will return by late morning.

Tonight’s NBM just available shows an additional 1.5 inches of rain through 7 AM Monday morning—

Tonight’s 00z NBM accumulated rain forecast from 8 PM Saturday through 8 AM Monday. (Click on image for a larger view.)

Incredibly, the remnants of Ophelia may keep showers with us much of Monday and there’s even a chance of showers on Tuesday.

Are the Phillies going to play today?

Updated Sat 09/23 @ 3:52 PM — Despite the weather, the MLB app says the Phillies will play this afternoon. Here’s the current radar at 3:41 PM—

Current radar at 3:41 PM Saturday. (Click on image for a larger view.)
Saturday Storm Update

Updated Sat 09/23 @ 12:12 PM — Don’t be fooled by the breaks of sun we’re seeing now due to ‘dry slotting’. There’s plenty of rain and wind on the way.

Water Vapor image showing ‘dry slot’ moving in from the southeast. It won’t last. (Click on image for a larger view.)

Updated Sat 09/23 @ 11:56 AM — As promised here is the latest GFS model, just available.

The GFS forecast position of the surface and upper low pressure at 8 AM Sunday—

GFS axis of heaviest rain on Sunday is much further west (white box) than previous forecasts which had the heaviest rain through Philadelphia. (Click on image for a larger view.)

This morning’s models continue with a similar forecast as those posted earlier with some differences—

Similarities:

  • Rain continues through Sunday.
  • Highest wind gusts to occur this afternoon and evening.
  • Model Position of upper low on Sunday is fairly similar.

Differences:

  • Axis of highest rainfall is further west with the GFS

I’m sticking with the HRDPS and NBM location of heaviest rain posted below.

Updated Sat 09/23 @ 10:11 AM — Latest (12z) NBM shows the expected additional rainfall forecast from 8 AM today through 8 PM Sunday evening—

Add these amounts above to the amounts from the MRMS graphic immediately below to get a handle on the total rainfall expected from this storm. (Click on image for a larger view.)

Updated Sat 09/23 @ 10:00 AM — Through 9 AM today, here’s the estimated rainfall received, based on the MRMS—

Received rainfall, MRMS estimated at 9 AM today. Contours are in mm. 25.4 mm = 1 inch. A large gradient exists in rainfall northwest of the city. Most models predicted this for today. (Click on image for a larger view.)

Updated Sat 09/23 @ 9:17 AM — I failed to mention with this update that at least half the rain from this storm will fall on Sunday, the other half today, Saturday.

Updated Sat 09/23 @ 8:54 AM — Ophelia has made landfall and is now a strong low pressure system. Here’s the current MRMS radar image with RAP model jet level windstream contours—

This morning’s 7:32 AM MRMS radar image with superimposed RAP Model streamlines. (Click on image for a larger view.)

The remnants of Ophelia are expected to curve back towards northern Delaware, as its circulation throws more moisture over our region.

No model will exactly predict the total amounts of rainfall in all locations, but I’m going to hang my hat on the HRDPS as a reasonable forecast—

Canadian HRDPS (06z) total rainfall forecast through 2 AM Monday morning. (Click on image for a larger view.)

Current NBM wind forecast meteogram for KLOM (Wings Field, Blue Bell PA

Here’s the NBM wind gust forecast for our region at the time of the scheduled Phillies game—

The next models, particularly the GFS, will become available about noon. I’ll update shortly thereafter.

Updated Fri 09/22 @ 10:32 PM — Tonight’s HRRR, RAP and the first 30 hours of the NAM. NAM-NEST and HIRESW models are in. The general trend is unchanged from my earlier 9:56 PM update.

The heaviest rains will be at the shore on Saturday, but significant heavy rain is forecast for the immediate Philadelphia area on Sunday. Totals for the two days remain a general 1.75-3″ in our area with 3-5+” possible as the shore.

Winds highest on Saturday. Here’s the latest NBM wind forecast for Blue Bell, PA—

Tonight’s 00z NBM wind meteogram for location Blue Bell, PA Mean Wind gusts 40 MPH. Standard deviation is dotted. (Click on image for a larger view.)

Update Fri 9/22 9:56 PM — The latest ECMWF and this afternoon’s NAM are forecasting the heaviest rain to occur on Sunday with the highest wind gusts Saturday afternoon and evening.

Updated Fri 09/22 @ 8:06 PM — The latest Canadian high resolution model (HRDPS) gives a very different forecast. This model only forecasts out 48 hours—

The latest (18z) HRDPS shows much heavier rainfall in our immediate area. The HRDPS was very good this past summer with thunderstorm predictions. I’m not sure that it will be as accurate with tropical or extra-tropical systems. (Click on image for a larger view.)

The HRDPS shows the highest winds about 9 PM Saturday evening.

Updated Fri 09/22 @ 7:54 PM — This afternoon’s GFS model has become available. It’s distribution of the heaviest rain is quite different than the earlier posted NBM model—

This afternoon’s (18z) GFS model shows most of the heaviest rain to the west of Philadelphia. Here’s the rain totals by Tuesday. (Click on image for a larger view.)

It should be noted that most models have reduced the peak wind gusts in our region to 35-40 mph on Saturday.

Previously Posted Fri 5:31 PM —

The model guidance was showing the development of this storm last weekend, which is impressive. At that time, I was saying that it looked like it would have “tropical characteristics” which meant that it had a warm core center.

Here’s the latest 12z NAEFS forecast for the current hour (4 PM Friday) showing the storm. The dull orange contour at its center is the 576 dm 500-1000 mb thickness line, indicating the storm’s warm core.

Today’s 12z NAEFS showing the Ophelia and its warm core center 9

Here’s the current water vapor image of the storm—

Water Vapor image at 4:30 PM with superimposed jet level windstreams and 500-1000mb thickness (RAP Model). Notice the 576 thickness center with upper winds shearing off to the west (blue). (Click on image for a larger view.)

Ophelia is expected to move into North Carolina and become non-tropical (“extra-tropical”) this evening upon landfall. Due to blocking high pressure to our north, the movement of this system will be slow and it will affect our region with rain and high wind gusts for much of this weekend.

Rain should begin here between 1AM and 3 AM Saturday morning and will continue on and off through at least Sunday.

The latest (12) ECMWF is not all that impressive with rainfall here —

ECMWF rainfall through Monday 2 AM. (Click on image for a larger view.)

The NBM rainfall for just for Saturday (from now through 2AM Sunday) is below—

This afternoon’s 18z NBM accumulated rainfall through 2 AM Sunday. (Click on image for a larger view.)
Tropical Storm Outlooks

ElSA

Fri 08:48 AM Forecast Review — The heavy rain had a sharp westward cutoff, as eventually predicted by the models late afternoon and evening yesterday.  Here’s radar image from 4 AM  showing the the heavy rain had a strong east-west cut off—
Radar 4 AM

Updated on Thu 10:46 PM Tonight’s models have reduced the amount of rainfall and moved the heavy rain further eastward.

Updated on Thu 7:30 PM highlighted below

The latest Canadian Regional GEM model captures the sharp western cutoff in expected heavy rainfall that several afternoon models are showing—

Canadian Regional GEM rain forecast captures the sharp cutoff in heavy rain just west of the city. (Click on image for a larger view.)

The latest ICON model, which did very well with last year’s tropical storms, has the heavier rain further westward.

ICON model total rainfall. (Click on image for a larger view.)

Updated on Thu 5:59 PM highlighted below

The afternoon model runs just are becoming available. The HRRR, the GFS and the HREF have a sharper cut-off of the heavy rain just west of Philadelphia with the heaviest rain most similar to the Model Blend NBM graphic below in the original post..

Updated on Thu 1:54 PM highlighted below

With the more westward track of the storm, the latest GFS has moved in the direction of the ICON and HREF models with 1.5-3.5″ of rain, extending into the Philadelphia area.

GFS model from 12z showing accumulated rain forecast by Friday morning.

The latest ICON model (which did very good with last year’s tropical systems) has less rain accumulation-

ICON model accumulated precip forecast from 12Z today. (Click on image for a larger view.)

Model Blend (which underestimated rainfall with last year’s tropical systems)

NBM (Model Blend) total rain forecast (Click on image for a larger view.)

see my Elsa post from Monday

A cold front is approaching from the Great Lakes and a pre-frontal trough will move through Thursday afternoon. Showers and thundershowers expected after 4 PM. Most of the thunderstorm activity will be expected in the far northwest areas, with heavy rain showers later this afternoon and evening in the Philadelphia area.

The remnants of tropical storm Elsa moves in later this evening and will affect us during the night time hours. The main effects of this storm will be high precipitable water and heavy rain. Not much wind expected (30 mph gusts), mostly at the shore. The storm exits early Friday morning.

Rainfall when it ends will be in the 1.5-2.5 1.5-3.5 inch range. Exact placement of the heaviest rain a challenge. The GFS keeps much of the heavy rain in NJ while the higher resolution models and the ICON have it overspreading the Philadelphia area. The Canadian GEM has the heaviest rain near Philadelphia! I’m leaning towards the heavy rain making it into Philadelphia.

GFS 1 hour 3 hour precip forecast for 3 AM Friday morning. (Click on image for a larger view.)
HREF precip Forecast for 4AM Friday showing heavier rain into the Philadelphia suburbs. (Click on image for a larger view.)