Summer Storms

THUNDERSTORMS THIS EVENING & WEDNESDAY

Forecast Updated Tue 5:40 PM — This afternoon’s HRRR and HREF models have the heaviest activity to our northwest—

This afternoon’s HRRR shows the storms mostly to the northwest at 8 PM. with storm motion vectors and shear vectors most aligned in these areas. We’ll see if the earlier HIRESW-ARW-MEM2 forecast from this morning does a better job with the thunderstorm placement than the more recent HRRR. (Click on image for a larger view.)

Tue 5:35 PM —Updated with storm motion/shear vector graphic from this morning‘s HIRESW

An upper air disturbance will approach Tuesday evening ahead of a cold front Wednesday.

Several parameters that are used to predict severity of thunderstorms are not all that impressive in the immediate PHL, in the low-moderate range. (CAPE values in the 600s)

Nonetheless, there are several factors including a strong jet streak to our northwest and considerable daytime heating to 82º that can create some interesting weather. Additionally, the storm shear vectors align with the predicted storm motion vectors, especially north west of our area, resulting in some stronger storms north and west.

Look for thunderstorms developing between 6 and 8 PM tonight.

This morning’s HIRESW simulated Radar with shear direction and motion direction vectors. at 7 PM and 8 PM Highest support is north and west of the city. (Click on image for a larger view.)

More on the thunderstorm threat Wednesday with a later post.