More thunderstorm indicies

[cloneofghosts]

The current setup for the thunderstorm text/icon is decent but it could be improved. Was chatting with AI to see what might be helpful without overcomplicating things and it gave me this:

Ingredient	Variable
Instability	CAPE (+ LI optional)
Moisture	2 m dew/RH
Cap	CIN
Lift	VVEL (omega)
Coverage heuristic	K Index (optional)

It also gave me this framework scoring system (but we can change it if we want) to better detect thunderstorms:

def calculate_thunderstorm_score(
    cape=None,
    cin=None,
    dewpoint_2m=None,
    omega_500=None,
    li=None,
    k_index=None,
):
    score = 0.0
    weight = 0.0

    # --- Instability (CAPE primary) ---
    if cape is not None:
        if cape >= 2000:
            score += 1.0
        elif cape >= 1000:
            score += 0.7
        elif cape >= 500:
            score += 0.4
        weight += 1.0

    # --- Lifted Index (fallback / boost) ---
    if li is not None:
        if li <= -6:
            score += 0.6
        elif li <= -3:
            score += 0.4
        elif li <= -1:
            score += 0.2
        weight += 0.6

    # --- Moisture (2m dew point) ---
    if dewpoint_2m is not None:
        if dewpoint_2m >= 20:   # °C (~68°F)
            score += 0.8
        elif dewpoint_2m >= 15: # (~59°F)
            score += 0.5
        elif dewpoint_2m >= 10:
            score += 0.2
        weight += 0.8

    # --- CIN (cap suppression) ---
    if cin is not None:
        if cin > -25:
            score += 0.6
        elif cin > -75:
            score += 0.3
        elif cin > -150:
            score += 0.1
        weight += 0.6

    # --- Lift (omega @ 500 mb, negative = upward) ---
    if omega_500 is not None:
        if omega_500 <= -5:
            score += 1.0
        elif omega_500 <= -2:
            score += 0.6
        elif omega_500 <= -1:
            score += 0.3
        weight += 1.0

    # --- K Index (optional coverage signal) ---
    if k_index is not None:
        if k_index >= 35:
            score += 0.6
        elif k_index >= 30:
            score += 0.4
        elif k_index >= 25:
            score += 0.2
        weight += 0.5

    if weight == 0:
        return 0.0

    return score / weight

def thunderstorm_text_from_score(score):
    if score >= 0.65:
        return "thunderstorm"
    elif score >= 0.4:
        return "possible-thunderstorm"
    else:
        return None

@alexander0042 Is this something that would make sense to add? I think most models have this data so it should be easy enough to add in.

[cloneofghosts]

Started on this branch https://github.com/Pirate-Weather/pirate-weather-code/tree/thunderstorm-updates

As noted in the comment:

• HRRR doesn't have vertical velocity
• ECMWF has vertical velocity but not convective inhibition
• NBM has none of the variables
• SubH has none of the variables

For ECMWF vertical velocity is on a pressure level and I don't know if that makes a difference to how the data is downloaded.