METEOROLOGIST MIKE MASCO: Severe Weather Potential: Southern New England Under the Gun Today

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Mike Masco

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Today will be an active severe weather day for much of Interior Southern New England.
The Storm prediction center in Norman Oklahoma has placed all of Eastern NY, Western Ma, NW CT, VT, and NH under a RISK area for strong to severe storms.

The model guidance from the 00z and 06z runs of the NAM , GFS, RAP, and RPM all show the liklihood of a volatile atmosphere going into 22z or 5pm this afternoon.

This is one particular sounding for Western Massachusetts via the 0z NAM. GENERALLY SPEAKING WE HAVE A MODERATELY UNSTABLE ATMOSPHERE GOING INTO THIS AFTERNOON.

CAPE:                 1700J/KG
LI:           -4.2
SWEAT INDEX:     315
SHOWALTER:       -1.7
HELICITY              182
TOTAL TOTALS:    52

BELOW I HAVE LISTED HOW THESE NUMBERS FIT INTO EACH SEVERE WEATHER PARAMETER WE FOLLOW. G

COURTESY OF METEOROLOGIST JEFF HABY AT THEWEATHERPREDICTION.COM

CAPE

1 - 1,500	Positive
1,500 - 2,500	Large
2,500+	Extreme

HELICITY

150-300	Possible supercell
300-400	Supercells favorable
400+	Tornadic possible

Showalter Index greater than 0: Stable, but weak with convection possible for SI = 1-2 if strong lifting is present.
Showalter Index between 0 and -3: Moderately unstable.
Showalter Index between -4 and -6: Very Unstable.
Showalter Index between less than -6: Extremely Unstable.

TOTAL TOTALS

<44	Convection not likely
44-50	Likely thunderstorms
51-52	Isolated severe storms
53-56	Widely scattered severe
>56	Scattered severe storms

SPEED SHEAR

0-3	Weak
4-5	Moderate
6-8	Large
8+	Severe

K INDEX

15-25	Small convective potential
26-39	Moderate convective potential
40+	High convective potential

CAPE

1 - 1,500	Positive
1,500 - 2,500	Large
2,500+	Extreme

SWEAT

150-300	Slight severe
300-400	Severe possible
400+	Tornadic possible

SR HELICITY

150-300	Possible supercell
300-400	Supercells favorable
400+	Tornadic possible

LIFTED INDEX / SWI

-1 to -4	Marginal instability
-4 to -7	Large instability
-8 or less	Extreme instability

BRN

<45	Supercells favorable
<10	Too sheared
teens	Optimum

EHI

EHI >1	Supercells likely
1 to 5	F2, F3 tornadoes possible
5+	F4, F5 tornadoes possible

Now, there is the threat of a few isolated tornadoes this afternoon should all go to plan.

This is a look at the winds from the surface to high aloft. We do have slight speed and directional shear going on with a south wind at 10MPH while a W/SW wind will be increasing due to the trough's interaction.

The winds between heights become unidirectional which may keep the storms moving and forming multiple cells into line segments.

HERE IS THE GRAPHICS FROM THE STORM PREDICTION CENTER. REMEMBER IF THREATENING WEATHER DOES OCCUR THIS AFTERNOON, KEEP IT TUNED INTO YOUR LOCAL ABC STATION.