Last Week’s Results

Tough week last week, with the major forecast bust I had on precipitation for Oct 9 for Omaha, plus generally underwhelming performances on temperatures the remainder of the week. Since I did pretty well the on the first city, and am better this week, my cumulative rank hasn’t gone down too much and I’m sitting at #263 nationwide (out of 1500) as of this writing.

Verifications

Below are the verified readings for each metric we were asked to forecast during last week, and a column showing error points I was assessed.

Post-Mortem

Day 1: Major bust across the board. Was off by more 5 degrees or more on both the high and low. This made up about half of the error points. The rest came from being off on max precipitation by more than 1.20”. MOS was considerably off the mark with temperatures – though NAM was closer. This was all due to the fact that a stationary frontal boundary never made it close enough to KOMA to realize warmer temperatures, and heavier precip. The axis of the 850 mb LLJ stayed south and east, along with the best surface convergence. As a result, nearly all of the model guidance was horribly wrong. The closest forecast in the class was still nearly 0.50” too high. I put too much credence into the upwards trends on the models – there were some indications already that KOMA was trending to be on the drier side of this event. Still, even if I had nailed the precipitation forecast, I would have busted hard on the temperatures. Need to be a lot more cautious going forward about situations where a frontal boundary and precipitation are around, and probably hedge down on temperatures during transitional seasons when a forecast site could be on the cold side of a front with rain.

Days 2-4: Much better forecasting overall, especially in regards to precipitation. However, got a lot of error points for being too cold across the board with temperatures. Buying into the colder temperatures in MOS made for an overall forecast that was too cold.

Forecasting for Week 2 at KOMA (Omaha, NE) Oct 16-19

Synoptic Set Up

A much quieter weather week is in store for Omaha. With high pressure building, most of the forecast week will see sunny or clear conditions. Light synoptic flow suggests the possibility for winds decoupling at night, giving rise to highly favorable conditions for strong radiational cooling. Temperatures will be trending up through the week as a upper-level trough moves east and heights continue to build.

Notes

NAM MOS guidance seems to be the preferred alternative with respect to overnight lows, given that forecast soundings show a clear signal for nocturnal inversions. Our class discussion notes that 1.4” of snow fell at KOMA over the weekend. Temperatures are in the mid-40s today, but cold overnight lows may mean that we need to consider patchy snow cover in forecasting overnight lows. Since overnight lows are expected to be quite cold to start the week, daytime highs should also be below normal for this time of year. The NWS official forecast does show a warming trend in overnight lows through the week. Delta Method was suggested as a possible approach, and makes sense with how similar the air masses will be day to day. The trickiest part of the forecast this week will be how cold overnight with conditions conducive to strong radiational cooling, and just how much things can warm up during the day.

Forecasts Submitted

This only reflects finalized forecasts, I’ve made small adjustments to the forecast based on checking MOS daily.