Monday, July 18, 2022

Weather Relief

I'm traveling at present and can't comment in detail, but major weather relief has arrived at last when it comes to Alaska's nasty fire and smoke season.  A change of pattern was advertised well in advance by the Climate Prediction Center, and widespread rainfall has been a big help for fire-fighting efforts.  Here's a temperature anomaly plot for Fairbanks and the latest 7-day precipitation analysis from the NWS:

The 30-day departure from normal analysis (below) now shows some green across southern Alaska, but notice how much brown there still is on the 90-day anomaly map (also below).  The drought isn't over yet.

Returning to the topic of lightning, a few days ago I witnessed an impressive night-time display of lightning in Florida, and I got to thinking about the contrast in lightning density between the two states: Florida having the most lightning per square mile, and Alaska the least.  Based on the BLM/ALDN data, Alaska's peak lightning density has been about 5 strikes (cloud or ground) per square km over about 11 years, i.e. approximately 0.5 strikes per km2 per year; this lightning hotspot is just to the north of the Alaska Range, roughly between Minchumina and Healy.

In contrast, the entire state of Florida averages about 7 strikes per km2 per year, according to a 10-year study from Vaisala, and some areas have considerably more.  So even the most lightning-prone parts of Alaska don't come close to what's considered normal in the so-called Sunshine State.  As far as I'm concerned, less lightning is always better, although it can be a visual spectacle: here's a video taken by my daughter last Wednesday evening as we were driving in Florida (apologies for inferior quality).  It would be interesting to dig through the Alaska lightning data to find the single most prolific lightning storm and see how it compares to these flash rates.


  1. I've yet to experience a prolific lightning storm like that in Alaska

    1. Thanks for the comment, Gary. It's an interesting question as to the meteorological constraints on maximum lightning generation in Alaska.

    2. What's the meteorological source or event for those prolific lightning storms? I recall them in the Midwest as a youth near the Great Lakes, but never here. Typically we get relatively isolated cells and occasionally adjacent buildups, but rarely something I may be misnaming by calling it frontogenesis. Usually when there Sun moves west or clouds intervene in insolation the storms collapse and abate. There it's night and they're still crackling away.

    3. It seems this was just an unusually long-lived instance of diurnal pulse-type convection, which is often very intense in Florida's summertime wet season. The abundant low-level humidity and strong daytime heating create very substantial instability, and given a favorable inflow of warm/moist air, storms can linger after nightfall. They nearly always die out by midnight, however, and often the sky is completely clear by morning.

      In the Midwest it is more common to have frontal processes that generate intense long-lived storms day or night.