How high will it go WED in the SE

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USAwx1
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How high will it go WED in the SE

#1 Postby USAwx1 » Tue Jul 13, 2004 7:38 pm

And yes it is going to be a VERY hot day from ERN VA through NC, SC, GA and even NRN FL on WED. And especially look out interior SC and extreme east-central GA which could broil under 850H temps of +22 to 23 DEG C!

But first before we get into that; let’s learn how to predict daily MAX temperatures using geopotential thicknesses.

Geopotential thicknesses are used to define the difference in geopotential height between two specified layers and will be proportional to the mean VIRTUAL temperature within the layers in question. Thicknesses may also be used to determine areas of temperature and moisture advection. For example warm air will have a higher thickness b/c it is not as dense and expands, while cold air will have the opposite (lower thickness) since it’s more dense and sinks.

Normally most forecasters are concerned with 1000-500mb for reasons such as deciding precipitation type during the winter as well as the separation of air masses from one another. The 510 meter thickness line will normally separate ARTIC air from polar air, the 540 meter line is normally the rain/snow cutoff line (rain south of the line and snow north) and the 570 meter line is the demarcation boundary between tropical and mid latitude air masses. These (510, 540, 570 meter) thickness lines will usually appear in most plots as SOLID lines, while other thickness lines will be DASHED.

Here, we are focusing on lower-level partial thicknesses to determine MAX temps. Or more specifically, we’re using the thickness of the 1000-850mb layer to forecast the daily maximum temperature.

Massie and Rose (1997) first studied the use of ETA-forecasted low level thicknesses in forecasting Daily MAX temperatures, but the regression equation which was derived from the data in the study was NOT proportional to the time of the year. A later study focused on the collection of data from 802 days with 65% of total sun.

A new set of regression equations were developed from the data which relates the Daily maximum temperature (Tmax) to the 1000-850mb thickness value and the time of year (i.e. sun angle). The Equations are listed as follows:

Winter: Tmax = 0.36 * Thk 850-1000mb – 422
Spring: Tmax = 0.33 * Thk 850-1000mb – 381
Summer: Tmax = 0.30 * Thk 850-1000mb – 338
Fall: Tmax = 0.35 * Thk 850-1000mb – 414

Where, Tmax is the Maximum daily temperature, Thk 850-1000mb is the 1000-850mb thickness value (in meters).

Back to the heat in the SE. This afternoons ETA had widespread 850H temps of > 20 DEG C over the region with an area of +22 to +23 DEG C over interior SC and East-central GA as noted at the beginning of the post.

Image

Meanwhile, LLVL thickness values are PROGGED between 1435 and 1450 meters with the HIGHEST values centered over Interior SC and E central GA. Using the methods we have discussed above for determining the MAX temperature based on these values, areas could see Highs up to 97F !!

850H temps of +20-23 DEG C suggest 95-100F (35-38 DEG C) given near full sun in all locations. This also is proportionate with what the low level thicknesses would suggest.
There will be a mean NW flow in the lower levels which is a strong downsloping component east of the Appalachians and could POSSIBLY boost temps up above 100F in some areas.

It will be harder further north to get the FULL potential out of the warm 850mb temps due to cloud debits or anvil blow off from possible ongoing MCS over the northern Mid Atlantic. Thus, it will be warmer further south into the Carolinas where there will be more sun and stronger surface heating.

Soil moisture is still somewhat LOW over the Carolinas and Georgia which will add to the excessive heat potential.

Image

In summary, I expect WIDESPREAD 95-100F readings over the SE on WED afternoon w/ a few areas possibly exceeding 100F. With the northwest flow, dewpoints may be lower over the interior portions of the Carolinas and GA (perhaps in the Upper 60s or lower 70s) which should cut down on the heat index, keeping it within a few degrees of the Actual temperature.

Records for the day may be in trouble as well in the warmer locations.

MAV numbers at CLT, GSP, CHS, and NBC suggest 90s to 100F as well. With lower dewpoints inland and OPPRESSIVE numbers closer to the coast. It is in those locations where heat index values could reach dangerous levels given the combination of the abundant moisture and VERY high temps.

http://www.nws.noaa.gov/cgi-bin/mos/get ... S&sta=KGSP
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#2 Postby USAwx1 » Tue Jul 13, 2004 9:15 pm

0z 7/14 ETA streaming in (out to 18hrs as of this posting) and is looking similarly warm with widespread +20 DEG C 850H temps over the SE with the compounding problem of W and NW downsloping flow over the region due to 850H ridge anchored over TX transporting the VERY warm air from the desert regions Eastward.

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Image
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#3 Postby USAwx1 » Tue Jul 13, 2004 9:37 pm

SVR weather will be a problem over the SE and Mid Atlantic region as mid and upper trough undergoes amplification overnight and tomorrow -- eventually taking on a NEGATIVE tilt over the lakes as associated mid-level jet approaching the base of the trough from the NW overspreads the region helping to contribute to enhanced deep-layer shear.

Steep height falls are on the order of 40m are forecasted over the northern Mid-atlantic region during the later afternoon hours in response to the aforementioned trough amplification as upper level divergence increases large scale ascent.

CAPE is expected to be > 2000J/kg from PA on Southward beneath 6-km shear of 30-40 KT. This will be sufficient for an organized severe weather event.
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#4 Postby USAwx1 » Wed Jul 14, 2004 12:19 pm

Currently at CLT the temp was 87F and the Dewpoint 64F, GSP had 81F w/ a dewpoint of 70F, NBC was roasting under 93F and a dewpoint of 76, which is yielding a Heat index value of 105F!!

CHS was not much better w/ a temp of 93F and dewpoint of 76F. This is leading to a heat index of 104F.

So far the above forecast for widespread 95-100F is looking to be in good shape.
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chadtm80

#5 Postby chadtm80 » Wed Jul 14, 2004 1:31 pm

Image

Click Link below to zoom in on your location

http://www.storm2k.org/ham/hw3.php?conf ... &plot=temp
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#6 Postby USAwx1 » Wed Jul 14, 2004 3:03 pm

http://www.storm2k.org/ham/hw3.php?conf ... iod=&dpp=0

As forecasted widespread 95 to 97F heat across SC. Dewpoints over the Upstate are still moderate and the heat index not as oppressive as it is near the coast. The dewpoints at CHS and Hilton head island were around 74F

http://www.storm2k.org/ham/hw3.php?conf ... plot=dewpt
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#7 Postby USAwx1 » Wed Jul 14, 2004 3:56 pm

Allendale SC has 98F as we speak. Hottest reading I could find at the current time in SC.

Macon GA was the hottest overall w/ 100F and a Heat index of 103F.
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#8 Postby chadtm80 » Wed Jul 14, 2004 4:58 pm

SWEATING MY ARSE OFF!!! Bring on the winter already
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#9 Postby USAwx1 » Wed Jul 14, 2004 5:20 pm

This Thread by Don, Aquawind and I should bring the winter into an early perspective for you.

BTW, FL dry season is looking wetter than average also. And cooler too.

Your Not along WRT sweating your arse off. LOL. My central Air unit is broken. And No one will be out to fix it til FRI afternoon. :cry:
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#10 Postby USAwx1 » Wed Jul 14, 2004 9:27 pm

So, Exactly HOW HIGH did it go today in the Southeast?

My forecast from Yesterday evening called for widespread 95-100F across the SRN carolinas and GA.

Here were the actual highs from a few locations in NC, SC, and GA this afternoon:

AGS: 97F
CLT: 91F
CHS: 97F
GSP: 91F
NBC: 96F
MCN: 100F
Average: 95.3F
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