August Wrap Up

We have another hot day in store for the state of Michigan.  Temperatures are expected to be in the upper 80s to low 90s with dewpoints in the low 70s by this afternoon.  Surface winds will be around 10 mph out of the west.  Below are the current Lake Michigan water temperatures.

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August Weather Summary

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Grand Rapids Forecast

[pdf-embedder url=”https://michigan-weather-center.org/wp-content/uploads/2023/09/94-grr.pdf” title=”94 grr”]

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U.S.A and Global Events for September 4th:

1766: A hurricane made landfall at modern-day Galveston, Texas. The following is from David Roth of the Weather Prediction Center. “A mission, named San Augustine de Ahumado was located in what is nowadays known as Chambers County. This mission was destroyed and subsequently abandoned. A seven-foot storm surge put the area under water. A richly laden treasure fleet of 5 galleons en route from Vera Cruz to Havana was driven ashore and had to wait many weeks for assistance to come. La Caraqueña wrecked on Galveston Island while El Nuevo de Constante sank along the western Louisiana coast. Fortunately, much of the treasure and people aboard were saved.”

1941: A violent tornado ripped through Northeast and North Minneapolis shortly afternoon on this day. The hardest-hit location was the Soo Line Railroad’s Shoreham Yards where four people died, and at least 50 were injured. The death toll at Soo Line could have been higher, but the tornado struck five minutes after the lunch bell went off, meaning 100 men left the shops. Click HERE for photos from Historic Minneapolis.

2000: Houston and College Station, Texas recorded their hottest day on record when highs reached 109° and 112° respectively. Houston has tied their record on August 27th, 2011. Other daily record highs included: Wichita Falls, TX: 111°, Waco, TX: 111°, Dallas, (DFW), TX: 111°, Austin, (Bergstrom), TX: 110°, Austin (Camp Mabry), TX: 110°, Dallas, TX: 110°, Victoria, TX: 110°, San Antonio, TX: 109°, Shreveport, LA: 108°, Corpus Christi, TX: 107 °F.

2007: Hurricane Felix came ashore in the pre-dawn hours as a Category 5 storm on the northeastern coast of Nicaragua. At the time of its landfall, the maximum sustained surface winds were approximately 160 mph. Felix killed at least 130 people along the coast, with damage in Nicaragua totaling $46.7 million. Click HERE for more information from NASA’s Earth Observatory.

2011: The center of Tropical Storm Lee moved ashore around sunrise. However, it would be a while before Lee would weaken to a depression as it remained nearly stationary while the southern half of the circulation was over water where it could continue to derive additional energy from the warm ocean. Lee brought torrential rains to Louisiana, Mississippi, and Alabama. Click HERE for more information about the NWS Office in Mobile, Alabama.

2016: An EF1 tornado developed in the open country area north of Merna, Wyoming. The tornado caused tree damage along its 2.45-mile path. At its widest, the tornado produced sporadic tree damage approximately 300 yards across. The trees fell on some fence lines but otherwise caused no property damage. Click HERE for more information from the NWS Office in Riverton, Wyoming.

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Forecast Discussion

Our main items of interest in the short term portion of the forecast
will be potential Heat headlines, and then shower/storm chances
beginning on Tuesday.

Really no concerns today with regards to heat headlines or storms
chances today. It will be very warm today as temperatures warm up to
around 90 degrees for most inland areas. This is supported by 850 mb
temperatures around 20C that would be able to mix down with plenty
of sunshine and a dry atmosphere above the boundary layer. Forecast
soundings show a cap remaining in place today with the upper ridge
still almost directly overhead today.

Things change a bit for Tuesday as the pattern shifts a bit. As the
upper ridge axis shifts east of the state, we will become more under
the influence of SW flow aloft. This flow will help to bring up the
upper low that is currently near the TX/AR border early this
morning. It will open up a bit before arriving here.

This flow and feature coming in will also drive dew points higher
into the mid 70s F. Combining this higher moisture with temps once
again expected to be in the lower 90s will help push heat indices up
into the mid to upper 90s. Right now, the threat for indices at or
above 100F long enough to meet criteria looks fairly low, and not
high enough to hoist a headline at this time.

The additional moisture streaming in will also assist with afternoon
convective development Tuesday afternoon away from Lake Michigan. MU
CAPEs will be approaching 2,000 J/kg per mean values from the SPC
HREF. The ridge axis being east of our area will allow temps aloft
to cool a little, and the cap to be eroded by Tuesday afternoon.
Deep layer shear is on the lower side, with only 15 to 20 knots of
deep layer shear. Pulse types of storms can be expected with
microbursts possible with an inverted V sounding evident. Divergent
flow and cooler temps near the lake will push any development inland
from around U.S.-131 and to the east.

...Showers and Thunderstorms Tue Night into Thu ...

There is somewhat of a potential for locally heavy rain for this
period.

One mid level wave will be tracking northeast through the CWA
Tuesday night.  It will be carrying some Gulf moisture with it as
PWAT`s climb to around 1.75 inches.  Instability advects in as well.
Thus with some moisture, lift and instability, a risk for
thunderstorms Tuesday night looks reasonable.

Surface based instability climbs during the day on Wednesday.
Ensemble mean values from the models are still up over 1000 J/kg.
The atmosphere remains moist with well above normal PWAT values
around. Meanwhile another mid level shortwave will be moving in from
the west in the afternoon. This feature will be slowing down as it
moves in.  An associated cold front pushes in during the late
afternoon or evening hours. The steady height falls combined with
the front moving into an unstable airmass should trigger numerous
showers and thunderstorms. Overall the deep layer shear remains
relatively low so the organized severe weather risk also appears
low. The low levels remain convergent into the night with
instability continuing so the risk for scattered showers and storms
to persist exists. 

PWATS remain relatively high on the backside of the departing wave
for Thursday.  We did bump up POPs somewhat for Thursday as lift
persists.  Ensemble QPF trends from most models indicate an
increased potential for precipitation on Thursday.  The 00z
deterministic ECMWF came in rather wet for Thursday as well.

Given the multiple rounds of showers and thunderstorms, along with
above normal PWATs, the lack of any stronger mid level winds and
persistent convergence in the low levels, we could see locally heavy
rain during this period before the wave departs off to the east.