The NAM and GFS keep greater snow accumulations north and west of Southeast Michigan. The ECMWF and GEM keep higher snow totals more south into Southeast Michigan. In this week’s case, all four models and their progressive runs have been quite consistent. Usually, a weather model that produces similar forecasts for the same time period with each run can engender more confidence. The HRRR looks just 24 to 36 hours into the future and stops. Hence, they can peer two to ten days in the future. Their runs occur two to four times a day. Conversely, an hourly model like the HRRR can not look ahead as far out in time as the ECMWF, GEM, GFS or NAM models. Generally, the less frequent the run the further out in time a model can predict. QUICK ASIDE: It takes a tremendous amount of computing power and time for each run of a weather model. The High Resolution Rapid-Refresh (HRRR) model is produced hourly (up to 24 times a day). Many are produced as much as two, four or eight times a day. Computer models are produced not just once a day. The NAM and GFS do not match up as well.Ĭonsistency is another factor. The greater the match, the better that model may be at matching the future state of weather.Īs of now, the GEM and ECMWF models start with environmental conditions that are a better match to conditions on the ground at the time of their production. For many weather forecasters, a key indicator for whether a weather model may make a good prediction is how well the match is between that model’s simulation of current conditions and reality. At their initial point, they are also simulating current conditions. They simulate how the weather may be in the future. Numerical models for weather are a simulation. Initialization is the starting time for any model when it is produced. In synoptic meteorology and forecasting its initialization, initialization, initialization. In real estate it’s location, location, location. Here’s what goes into choosing which models may make more sense for any given time. The projected prolonging of wet and icy conditions reduces the snow totals in Southeast Michigan to 1 to 4 inches. So, greater amounts of snow that are 6 to 12 inches are possible in The Thumb and the Saginaw Valley according to these models. In fact, it snows sooner and longer not just north of 8 Mile Road but north of M-59 and into the Saginaw Valley. This means the full transition to snow occurs later rather than sooner in Southeast Michigan. This results in a longer period of transition from rain to snow Thursday with a greater chance of freezing rain and sleet. It has the same drop in temperatures at the surface where people, cars, trucks and houses are but temperatures aloft (inside clouds) either fluctuate near or are above freezing. These two models have the cold front forming and remaining farther west and north. Two other computer models, the North American Mesoscale (NAM) model and the Global Forecast System (GFS) model have the same cold front but take its origin (called frontogenesis) and trajectory in a very different way that results in drastically different snowy outcome (or not so snowy). By the end of Thursday evening, these models predict 3 to 8 inches of snow with much of it falling south of 8 Mile Road. The rapidly sinking mercury and persistently falling snowflakes combine to provide a significant amount of snow for most of Southeast Michigan from northern Oakland and Macomb Counties south through Detroit and Ann Arbor to the Michigan-Ohio Border. Snow lasts through much of the afternoon with this model as temperatures plummet. As it does, steady rain showers quickly change over to steady snow showers with not much sleet or ice. Two computer models, the Global Environmental Multiscale System (GEM) model and the European Centre for Medium Range Weather Forecast (ECMWF) model have a cold front developing and racing through the Motor City region Thursday morning. Here is a breakdown of this week’s computer models and decision to go with one versus another or combining elements of different models to help Southeast Michiganders get prepared not scared: A Tale of 2 Sets of Models Related: Wind, flood advisories, then winter storm watch in Metro Detroit: Significant snow coming Thursday Meteorologists take their education and experience to decipher which computer models are most relevant when figuring out the time snow will make its appearance the day after tomorrow. It is an eternity when it comes to numerical models and their digital prognostications. Computer models are a significant forecast for analyzing any prediction.Īs of Tuesday evening, snow is over a day and a half away. That’s when it’s up to the Local4Casters to provide on a top notch weather forecast. DETROIT – The ears of Detroiters perk up when snow is in the future.
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