FROM ROCKETS TO STORMS...
SHOT OUT OF A ROCKET
Before we get to the weather, I just wanted to take a minute to welcome the newest member of my weather team, meteorologist Nick Stewart. For his age, Nick is one of the most decorated forecasters in the country. He has won numerous Emmy's, Murrow awards, as well as multiple Midwest and Iowa broadcast News Association awards. His work has been seen on all the major cable and TV news networks around the country. He is a highly skilled meteorologist and exceptional storm chaser. His latest full-time employment has him working as a space flight meteorologist for the U.S. Space force. His responsibility is analysis and quality control of upper level winds, critical for rocket launches at the Kennedy Space Center and Cape Canaveral Space Force. No pressure there!
Nick is also 6'-7" tall and stands a full 9 inches taller than me. When we are storm chasing, the rain or hail always hits him first, meaning he always knows a second before me when precipitation begins or ends. That makes me so jealous! He can also dunk and I can't. Nick will be handling weekend forecasting details. I'm thrilled to have him aboard, and you should be too. The man is a bad hombre. Please join me in welcoming the "Rocketman" to TSwails.
Here's a video Nick produced about using high-resolution satellite imagery to find tornado tracks, making the Dec. 15, 2021 tornado outbreak the largest on record in the state of Iowa.
HERE COMES ANOTHER STORM...
We had more than our share of wild and windy storms in March, and now it's time for April to roar. Another impressive spring disturbance will swing through the Midwest Tuesday night and Wednesday, bringing an active round of showers and thunderstorms. There is a conditional threat of severe weather and some spots could also see some healthy rains, something we could all use.
The first sign of the approaching storm will be clouds, which rapidly thicken heading into the afternoon Tuesday. Warm air advection is surging northward ahead of the system and by Wednesday morning, water vapor is shown as high as 1.43 inches on the EURO. That's more than 300 percent above normal.
It's also 3-4 standard deviations above the norm for April 2nd.
The moisture will also be accompanied by a surge of warm air, but that remains well to the south Tuesday, marked by a warm front over SW Missouri. Locally, SE winds not conducive to warming keep highs in the low 40s north to near 50 in far southeast Iowa. While clouds increase, it appears the bulk of the day remains dry, with only a slight chance of a late day shower or sprinkle.
Tuesday night, rapid cyclogenesis take place over Kansas as an intense low level jet veers towards SW Iowa. As it arrives, (dragging the warm front along with it), strong moisture convergence pops thunderstorms that translate NE into my area overnight. The storms will be elevated north of the warm front in an environment ripe for hail due to meager surface based CAPE but high lapse rates. The bulk of the showers and storms may hold off until well past midnight. They also look a bit linear (banded) which means rain amounts may vary considerably from spot to spot. Here's a simulated radar off the 3k NAM for 6:00am Wednesday morning.
What happens with this initial round of convection will determine the threat for any surface based storms Wednesday. If the air mass can recover, the surface low remains in central Iowa at daybreak. It has a triple point, where a warm front arcs NE of the low and a cold front trails to its south. That delineates the warm sector of the storm where the instability necessary for severe storms is found. Note the temperatures have gone from the 40s and 50s Tuesday, to the low to mid 70s Wednesday afternoon.
Moisture is evident in the form of dew points, which the 3k NAM shows at 60 all the way to Dubuque.
There is also some CAPE or potential energy. It's moderate, but low level shear is significant in far SE Iowa and WC Illinois, where the severe weather threat looks greatest in my region.
At this point, it's a race for time as far as storms go. The cold front that initiates them is nearing the Mississippi near noon Wednesday and clears my eastern counties later in the day. At some time in its journey, storms will fire ahead of the front. The question is where and how soon? The 3k shows a clustering of helicity tracks through parts of SE Iowa and WC Illinois mid-Wednesday afternoon. These reflect where rotating long tracked supercells might develop.
They initiate around noon in SE Iowa and then build NE along the advancing front. This simulated radar shows them at 3:00pm advancing into the area where the helicity tracks are shown. Frankly, mesocale details are still not resolved which, until they are Wednesday, leave doubt as to the magnitude of the convection.
As of this post, SPC does have the area from the Quad Cities south and east in an enhanced risk (level 3 of 5) for severe thunderstorms. We should be able to fine tune the concern later Tuesday as timing and parameters become more certain. Something to keep a keen eye on, especially near and east of the Mississippi River. The speed of the cold front will dictate the ultimate strength of any storms in my area. A slower solution, more storms. A faster solution, fewer storms with lower strength values.
Due to the high level of moisture and significant dynamics (as well as thunderstorms), some areas are likely to see heavy rains where the strongest updrafts occur. Training or banding could also cause amounts to vary quite a bit as well. Here's what guidance is showing for rain totals Tuesday night through Wednesday.
The EURO
The 3k NAM
The GFS
The 12k NAM
The HRRR
Following this disturbance, cooler weather returns for the remainder of the week, with temperatures near to perhaps a bit below normal. The next storm chance comes Friday night or Saturday. Due to phasing issues, this is currently a low confidence period. As Nick noted yesterday, recent trends have been inching northward on the track, increasing the chances of precipitation at least reaching the SE half of my area. More on that as we get the first system behind us Wednesday. Get ready for some very changeable and potentially volatile weather conditions the next 24–48 hours. Roll weather...TS
