Author: Ben Castellani (Page 279 of 358)

Ben grew up in southwestern Pennsylvania and holds both a bachelor's and a master's degree in Meteorology, the latter being from CU Boulder. His hometown received nearly three feet of snow from the Storm of the Century back in March of 1993, sparking his initial interest in impactful weather. Ben currently works on remote sensing and data analysis software at NV5 Geospatial Software in Boulder.

DayCAST: Fri 07/28/17

July 28, 2017 / Ben Castellani

Rain chances are elevated again as a soupy monsoon airmass remains across Colorado. We should actually see a better chance of storms today as their is less capping aloft and slightly more moisture. With weak shear in place, today's storms could produce hail up to 3/4" in diameter along with heavy downpours. We're not expecting widespread flooding, but a few isolated …

DayCAST: Thu 07/27/17

July 27, 2017 / Ben Castellani

How about that slow-moving monsoon storm last night in Boulder….definitely our most intense rainfall since late last summer. Between 7and 9 PM, 0.5 to 1.0″ of rain was recorded as torrential rain pounded the city. The radar image from 7:42 PM is below, with the storm that affected Boulder circled in pink.

Radar image from Wednesday night at 7:42 PM. Monsoon storms!

Yesterday had a lot of solid meteorology working together to produce the heavier rainfall. Today we will not see quite as favorable of conditions. Moisture has dropped and the frontal boundary has pushed well south and east.

After morning sun, expect partly cloudy skies in the afternoon and storms forming after 2PM, first across the higher elevations. We expect storm coverage to be isolated across the Metro area, with scattered activity in the Foothills (especially south and west of Denver). Highs will remain cool in the lower 80’s.

Unsettled conditions will remain through the upcoming weekend, with at least isolated chances of storms each day.

Fujiwhara Effect!

While checking the health of our monsoon flow for this forecast, I noticed a rare phenomenon in the models that is expected to happen between two tropical systems off the western coast of Mexico in the coming days. It is known as the Fujiwhara Effect and it happens when two nearby low pressure systems (normally tropical cyclones) orbit each other and spiral closer together. You can see this happening in the animation below between Tropical Storm Irwin (left) and Hurricane Hilary (right). Here is some additional reading from Wikipedia on this rare effect if you are interested.

Animation showing a likely Fujiwara interaction between two tropical cyclones off the western coast of Mexico this weekend.

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DayCAST: Wed 07/26/17

July 26, 2017 / Ben Castellani

The cold front we mentioned in our weekly outlook on Monday has moved through during the overnight hours. You will definitely notice the change in airmass today as temperatures only peak in the upper 70's. This is a 10 to 15 degree drop from yesterday. Earlier in the week, the best upslope was forecast to setup across the Denver Metro …

DayCAST: Tue 07/25/17

July 25, 2017 / Ben Castellani

Following a hot and generally dry day yesterday, storm chances increase slightly today with the arrival of deeper monsoon moisture. The precipitable water anomaly map below shows that the most atypically moist area across the country includes Utah and western Colorado. Keep in mind that moisture anomaly is just that, an anomaly. It is slightly biased by the fact that …

This week in weather: July 24, 2017

July 24, 2017 / Ben Castellani

Much of our region has missed out on the monsoon thunderstorms so far. As we move into the last week of July, Boulder’s monthly rainfall total rests at just 0.32″. Normal for the month of July is right around 2″, so this is well below average. The week ahead will offer a resurgence of monsoon moisture to northeast Colorado. However, as always, not everyone will see the much needed soaking rains.

DayCAST: Thu 07/20/17

July 20, 2017 / Ben Castellani

As of late last night, the surge of monsoon moisture is now solidly across the central part of Colorado. Can you pick it out in the precipitable water anomaly map below? In fact, precipitable water values this afternoon and evening will approach 1.4" in the Denver Metro area, by far the "juiciest" air we have seen in 2017! This moisture …

DayCAST: Wed 07/19/17

July 19, 2017 / Ben Castellani

The monsoon plume continues to funnel subtropical moisture northward into Arizona, Utah, and parts of western Colorado today. The plethora of flood-related advisories tells the story: As we discussed in our weekly outlook, this moisture will slowly be migrating eastward through the week. With this, we expect slightly increased chances of storms in the mountains today, scattered coverage for the most …