Monthly Archives: October 2009
Happy Halloween!
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| It’s shaping up to be a nice day here in Northern Colorado weatherwise for trick-or-treating tonight. It’s currently in the upper 40′s to low 50′s throughout the area, mostly sunny, and the snow is melting. Temperatures will fall fast after dark with clear skies and some snow still left on the ground so bundle up! It will likely be in the 30′s by 9pm and should bottom out in the 20′s tonight in Northern Colorado. |
Snowstorm Winding Down in Greeley
After about 36 hours of steady light to moderate snowfall, we now have 10″ of snow on the ground in Greeley. Spotter reports of 10″ to 13″ have been common in the area. The big winners on this storm were Pinecliffe with 43.8″ and Black Hawk with 40″. The Front Range foothills and southwest Denver got the highest snowfalls with this storm due to a persistent terrain induced lift (upslope flow). Here in Greeley, we ended up getting snowfall totals within the lower end of our forecast range (of 10″-18″). We actually got a decent amount given a persistent low-level north to north-northwest wind. Here in Greeley, a N-NNW wind direction is associated with downsloping off of the Cheyenne Ridge and the mountains to our northwest, which tends to dry out the lower levels and reduce snowfall totals. Our optimal wind direction for upsloping and heavy snow is from the east to northeast.
Snowstorm Update: 24 Hours Into the Storm
Quick update: As of 12:00 am October 29th, we have 9″ of snow on the ground in Greeley, CO. I’m sure our actual snowfall totals are much higher, but due to settling and packing, there’s 9″ of snowpack. Our surface winds have come around to the northwest, which I suspect will dry us out and suppress any heavy snowfall potential for the duration of this event. Models are forecasting anywhere from another 2″-5″ inches for the next 24 hours. All in all, we have gotten (and will likely receive) what was forecasted… 10″-18″.
Snowstorm Update
I went out during lunch today to measure our snowfall total so far from our ongoing storm system. So far totals are not too impressive out on the Plains and we have about 4″ to 5″ here in Greeley (as of about noon on October 28th). The heaviest snow has been confined to the foothills as one would expect with northeasterly upslope conditions. As the low pressure system slowly moves into our area, I expect the snowfall rates to pick up quite a bit later today into tonight. Forecasts are still calling for up to 18″ of snow… we’ll see. The Storm Prediction Center has put out a mesoscale discussion that covers an area from Greeley northward into Wyoming. They say that snow should pick up in intensity here shortly.
Heavy Snow Over Northern Colorado
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A strong cold front pushed through northeastern Colorado during the evening hours of October 28th and moderate rain began to fall shortly after the frontal passage. By 9:30p mountain time the rain turned to light snow in the Greeley area. This photo was taken at 11:00p in Greeley just north of the UNC campus when moderate to heavy snow began to fall and a coating of wet snow began to blanket the ground. The current forecast is for 10″-18″ of snow from this storm system. |
Colorado Snowstorm On Its Way
A strong low pressure system is forecasted to begin to organized and wrap up over Utah on Tuesday and Wednesday October 27 and 28th. Tonight both the NAM and GFS forecast models are in agreement and have the low pressure system tracking slowly across southern Utah and southern Colorado Tuesday, Wednesday, into Thursday morning and then hooking northeastward into far northeastern Colorado and southwest Nebraska on Thursday afternoon/evening. Right now it looks like light snow will begin falling sometime late Tuesday night into Wednesday morning over southeastern Wyoming and it will develop southward into northeastern Colorado shortly after (especially near the foothills). The general consensus is that the heaviest snow will fall Wednesday or Wednesday night over the Colorado Front Range urban corridor. The GFS predicts the heaviest snow to begin falling early Wednesday morning through Wednesday evening while the NAM holds off the heaviest snowfall until Wednesday evening into early Thursday morning. (more…)
29 April 2009 Event: Discovery Storm Chasers Trailers
Discovery posted a few trailers for this Sunday’s episode. This was early in the season and I was out with TWISTEX working on the mobile mesonet data acquistion system… we saw some tornadoes and got really stuck in the mud!
Richard Heene: Scientist? Meteorologist? Really?!
| I know, I know, we’ve heard enough about this nut case and the more people publish stuff about him, the more we contribute to his ultimate scheme. However, I want to set the record straight on a few things. I am a trained meteorologist and experienced storm chaser from Colorado and when I first got word of this story it really got my attention. |  |
29 April 2009 Cedar Hill, TX Tornadoes: Case Study
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At least 2 tornadoes were observed on 29 April 2009 by myself along with TWISTEX in Floyd County Texas near the town of Cedar Hill. Cedar Hill is a small town east of Plainview on the edge of the Cap Rock. This was my first chase of the 2009 season and I was testing out the new mobile mesonet data acquisition system that I had redesigned during the previous months. The instruments were not yet calibrated and we only had one mesonet system out on this event so I don’t believe any meaningful data was collected. |
| The atmosphere on this day was prime for severe thunderstorm and supercell development. There was a dryline running north to south through the Texas panhandle with an outflow boundary triple point just north and east of Plainview by mid afternoon. The storm of interest developed on the dryline west of Plainview. As it moved off the dryline it interacted with the outflow boundary rapidly causing the storm to go from high-based outflow dominant to low-based tornadic. A NAM sounding from 0000 UTC near Cedar Hill, TX is shown here (click on the image for a closer view). It showed a decent amount of CAPE with 2347 j/kg, a lifted index of -6.7, and a nice looking hodograph with 220 m2/s2 of 0-3 km storm relative helicity, which resulted in an EHI of 2.9. The mid level flow was a bit lacking with only 35 kt at 500 mb, which might have contributed to this day not producing too many tornadoes. If it wasn’t for the storm/boundary interaction there likely would have been no tornadoes in the panhandle on April 29th. |  |
Does El Nino Impact Colorado Snowfall?
With weak to moderate El Nino conditions expected for the Winter of 2009-2010, I was curious as to what impacts it might have on seasonal snowfall totals across Colorado. I did a quick study by looking at annual snowfall totals for Greeley, Evergreen, and Breckenridge, CO for the winter seasons of 1972-73 through 2008-09 during La Nina, ENSO-neutral, and El Nino years. I picked each of these locations to represent the Colorado Front Range Plains, Foothills, and Mountains respectively.