Chance of early Feb rain still ahead, and I can prove it. This panel below is from last night’s 5 PM AST global data ingest into the WRF-GFS model, our best, as rendered here by IPS MeteoStar. As you can see, there are quite a few acres of rain showing up in southern Arizona on the 5th at 11 AM AST. I’ve added an arrow to help you find it.
A low center is positioning itself off Baja as we speak, in almost exactly the same spot as the one that gave us our drenching rains of a couple of weeks ago. But, like a raggedy-looking hitchhiker that no one picks up, there’s no interaction with this developing low center down there by a trough zipping by in the westerlies to the north of it, one that dips down to the south just that bit and scoots our promising low and all its water to Arizona. Before that happens, that low wanders around and dies a quiet death down there.
When low centers are as far south as this one that is developing off Baja and over the warm waters out there, it’s cool center gradually warms up due to all the Cumulonimbus clouds it spawns, that warm air shooting up into its center and around it, and the circulation around it dies; it gradually just goes away. This is because there is no longer any temperature contrast between the center and regions outside of it, that which drives the circulation: no temperature contrast, no circulation.
You can see what happens to that low center in the panel above when no trough ejects it right away toward Arizona and it has to survive on its own in the next forecast map below.
Yesterday’s cloud sequence, a classic one we see over and over again
First the thin Cirrus or Cirrostratus. Then, as though a real storm was coming, the sky lowers and thickens up in Altotratus. It non-desert locations, this sequence to Altostratus leads to rain about 70% of the time, that number from ancient cloud observation studies conducted before satellites and models. Finally, the back of the “storm”, well, at 25,000 feet you would’ve have thought is was a “storm” with all the snow that fell on you. Here is the start, middle and end, the latter of our fabulous sunset:
A look back at our end of January rainstorm