Fizzle factor: How drought keeps rain away
Stop me if you've heard this one before: what looks like a certain soaker a few days out ends up giving Michiana just a few drops by the time the storm moves out.
It's been the story of March, as we are on pace for the driest March on record in South Bend.
The main culprit: the ongoing drought across Michiana.
While we're about two inches of rain behind schedule for 2021, most of the area has a rainfall deficit of more than eight inches since July 2020.
From a forecasting standpoint, prolonged drought can be especially frustrating.
Meteorologists rely on computer models to accurately forecast weather conditions. There are long-range models (like the GFS, European, and Canadian) and short-range models (like the HRRR, RAP, and SREF). Generally speaking, long-range models give us a broad-strokes look at the upcoming weather patterns, while short-range models give us more specifics.
While long-range models can try to tell us when low pressure systems will arrive and how potent they will be, their scale is too big to "see" the drought in Michiana. So, forecast rain amounts might look impressive on multiple models three or four days out. However, once we get closer to the event (most short-range/high-resolution models have data ranges of 1-2 days), forecast rain amounts will decrease. Short-range models pick up on more local conditions (like the drought) and adjust the numbers accordingly.
At this point, Thursday's rain looks promising, with most models pointing to around an inch of rain by the end of Friday for Michiana.
With our abnormally dry conditions, however, don't be surprised if these numbers trend downward over the next 24 hours.
But the drought doesn't just mess with model data, it also messes with the RADAR and with the rain itself, too.
3:30 PM -- There is rain on the radar but will anyone see more than a few drops?— Tom Coomes (@TomCoomes) March 23, 2021
Look how low the RH is, the air is dry. This is the drought 'fizzle factor' as it zaps the would-be rain before reaching the ground.
Share your reports. #inwx #miwx pic.twitter.com/z2GkEhu00K
The dry air tends to zap whatever rain is falling, especially if the rain isn't particularly heavy. Often, light rain will evaporate before it hits the ground, leading to barely measurable rain amounts that won't put any dent in the drought.
Our best chance of seeing needed significant rainfall is on Thursday. Stay with ABC57 News for the latest forecast updates.