Graphical Weather Forecast

Northern Alabama - Decatur - Priceville

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Severe/Hazardous Weather, Huntsville Office, National Weather Service
Storm Prediction Center, NCEP, NWS

Weather Station at Pryor Field, Decatur, AL - Conditions - Last Three Days | Meteogram

Station KEET in Birmingham, AL

Sounding for Decatur, AL

Skew-T Questions

Questions concerning values displayed on the SKEW-T graphic that expand understanding of the stability of the air mass over this area, together with its potential for severe weather:

Sounding variables and indices

Y / N - L57 Lapse Rate: Greater than 5.5° C/km? greater than 6.7° C/km?
Y / N - Is the Theta-E Index greater than 5? Greater than 8?
Y / N - Lifted Index (LI): Less than -4? Less than -8?
Y / N - Showalter Index (SI): Less than -4? Less than -8?
Y / N - Total Totals Index (TT): Greater than 53? Greater than 56?
Y / N - K Index (KI): Greater than 26? Greater than 40?
Y / N - SWEAT Index (Severe Weather Threat Index): Greater than 300? Greater than 400?
Y / N - Energy Index (EI): Less than 0? Less than -2?

Parcel Indices

Y / N - CAPE ( Convective available potential energy): Greater than 1,500? Greater than 2,500?
Y / N - CINH (Convective inhibition): Greater than 51? Greater than 200?
Y / N - CAP: (Cap strength): Greater than 2.0? Greater than 4.1?
Y / N - Super-adiabatic lapse rate – where the temperature decreases with height – at a rate of greater than 10 degrees Celsius per kilometer? (data is displayed on the NWS Skew-T Sounding Charts in the lower left corner)

Wind Parameters

Y / N - HEL (Storm relative helicity): Greater than 300? Greater than 400?
Y / N - EHI (Energy-Helicity Index): Greater than 1? Greater than 5?
Y / N - BRN (Bulk Richardson Number): Less than 45? In the teens?
Y / N - Upper level winds (between 500 and 300 mb level) of greater than 100 knots?
Y / N - Low level winds (850 to 700 mb) at 25 knots or greater?
Y / N - Atmospheric winds increasing at higher levels (upper level speed shear greater than 70 knots)?
Y / N - Atmospheric winds from different directions (directional shear of 60 degrees or more from the surface to 700 mb)?

Current Surface Conditions

Y / N - Dew Point greater than 55 degrees?
Y / N - Temperature greater than 80 degrees? In the forecast? - Y / N (High temperature and high dew point indicates high instability, increasing the threat of severe weather.)
Y / N - Relative Humidity (RH): Greater than 50%? Greater than 80%?
Y / N - Is there a 30 to 50 degree surface temperature/dew point spreads? (High microburst potential.)

When these values indicate the potential for severe weather, or where there is some questions about the values displayed on the graphic, I bring up the Text version of the SKEW-T and check the appropriate values.

PW - Moisture Content:

0.50 inches or less = Very low
0.50 to 1.25 inches = Low
1.25 to 1.75 inches = Moderate
1.75 to 2.00 inches = High
2.00 inches or above = Very high

Dew Point

Greater than 75° = Very high

65-74° = High

55-64° = Moderate

Less than 55° = Low

Low Level Jet

Greater than 70 knots = Extremely high

50-69 = Very high

30-49 = High

20-29 = Moderate

Less than 20 = Low

Additional Variables to Watch: Vertical Wind Shear, Veering, Mid-level Cap, Helicity.

Hazardous Weather Outlook

Area Forecast Discussion

Day One Convective Outlook

National Forecast Model Maps
National Weather Service

Short Range
24 hour
48 hour

Medium Range
Day 3
Day 4
Day 5
Day 6

A few of the additional weather pages on this web site:

Huntsville Weather Forecast Office, National Weather Service

Short Term Forecast (The 6-Hour NOWCAST).
Not issued during fair weather. Access only during inclement weather; carefully check the date and time.
Special Weather Statements
Issued infrequently; carefully check the date and time.
Storm Reports
Storm specific; carefully check the date and time.

Storm Prediction Center: Watches, Mesoscale Discussions, Outlooks

Amateur Radio Fact of the Day

AF4AX