We reached 60° yesterday for our high temp. Our high for today was at midnight with 53° with another rain total in the hundredths of an inch.
Overall a blustery damp day is in store with a good deal of cloud cover hanging in across the area. Thinking we may see some wind gusts this afternoon increase towards advisory levels, but expecting most gusts to remain in the 30-40 mph range. Rain and snow showers are on the menu with an inch or two possible north of Grand Rapids.
In some of our forecast discussions, you may have seen the mention of Rossby waves. Below is an explanation of the movement of air in our atmosphere which is like a great ocean above us. Just as the oceans have currents so does our atmosphere.
Rossby waves naturally occur in rotating fluids. Within the Earth’s ocean and atmosphere, these planetary waves play a significant role in shaping weather. This animation from NASA’s Goddard Space Flight Center shows both long and short atmospheric waves as indicated by the jet stream. The colors represent the speed of the wind ranging from slowest (light blue colors) to fastest (dark red).
Oceanic and atmospheric Rossby waves — also known as planetary waves — naturally occur largely due to the Earth’s rotation. These waves affect the planet’s weather and climate.
Oceanic Rossby Waves
Waves in the ocean come in many different shapes and sizes. Slow-moving oceanic Rossby waves are fundamentally different from ocean surface waves. Unlike waves that break along the shore, Rossby waves are huge, undulating movements of the ocean that stretch horizontally across the planet for hundreds of kilometers in a westward direction. They are so large and massive that they can change Earth’s climate conditions. Along with rising sea levels, King Tides, and the effects of El Niño, oceanic Rossby waves contribute to high tides and coastal flooding in some regions of the world.
Rossby wave movement is complex. The horizontal wave speed of a Rossby (the amount of time it takes the wave to travel across an ocean basin) is dependent upon the latitude of the wave. In the Pacific, for instance, waves at lower latitudes (closer to the equator) may take months to a year to cross the ocean. Waves that form farther away from the equator (at mid-latitudes) of the Pacific may take closer to 10 to 20 years to make the journey. The vertical motion of Rossby waves is small along the ocean’s surface and large along the deeper thermocline — the transition area between the ocean’s warm upper layer and colder depths. This variation in vertical motion of the water’s surface can be quite dramatic: the typical vertical movement of the water’s surface is generally about 10 centimeters, while the vertical movement of the thermocline for the same wave is approximately 1,000 times greater. In other words, for a 10 centimeter or less surface displacement along the ocean surface, there may be more than 91.4 meters of corresponding vertical movement in the thermocline far below the surface! Due to the small vertical movement along the ocean surface, oceanic Rossby waves are undetectable by the human eye. Scientists typically rely on satellite radar altimetry to detect the massive waves.
Atmospheric Rossby Waves
According to the National Weather Service, atmospheric Rossby waves form primarily as a result of the Earth’s geography. Rossby waves help transfer heat from the tropics toward the poles and cold air toward the tropics in an attempt to return atmosphere to balance. They also help locate the jet stream and mark out the track of surface low pressure systems. The slow motion of these waves often results in fairly long, persistent weather patterns.
Longwaves and Shortwaves
Longwaves
The hemispheric weather patterns are governed by mid-latitude (23.5°N/S to 66.5°N/S) westerly winds which move in large wavy patterns. Known as planetary waves, these longwaves are also called Rossby waves, named after Carl Rossby who discovered them in the 1930s.
Rossby waves form primarily because of the earth’s geography which does two things. First, the earth’s heating from the sun is uneven due to the different shapes and sizes of the land mass (called differential heating of the earth’s surface). Second, the air can’t travel through a mountain so it must rise up and over or go around.
In both cases, the disruption of the air flow creates imbalances in temperature distribution both vertically and horizontally. The wind responds by seeking a return to a “balanced” atmosphere and changes speed and/or direction. However, as long as the sun keeps shinning, those imbalances will continue to develop. Thus, the wind will constantly be changing directions, and develop into wave-like patterns.
The length of longwaves vary from around 3,700 mi (6,000 km) to 5,000 mi (8,000 km) or more. They generally move very slowly from west to east. But occasionally they will become stationary or retrograde (move east to west).
The speed at which these large waves move should not to be confused with the speed of the wind found within the waves themselves. For example, there can be a strong jet stream wind of 100 kt (115 mph / 185 km/h) moving through the longwave but the position of long wave itself move may very little. The wave itself is not moving at 100 kt (115 mph / 185 km/h), just the wind within.
Rossby waves help to transfer heat from the tropics toward the poles and cold air toward the tropics trying to return the atmosphere to balance. They also help locate the jet stream and mark out the track of surface low-pressure systems. The number of longwaves at any one time varies from three to seven though it is typically four or five.
Their slow motion often results in fairly long persistent weather patterns. For example, locations between the trough and the downstream ridge can experience extended periods with rain or snow while at the same time 1,500 – 2,000 miles (3,000 – 4,000 km) upwind and/or downwind the weather is very dry.
This often can lead to a misconception where one assumes the weather he or she experiences is typical everywhere. That is simply not true. If one place is receiving cooler weather and/or flooding rains over a period of several days to weeks, then there are some other places where the weather is warm and dry for about the same period. It all depends upon the location of the longwaves relative to the observer.
Shortwaves
A “piece of energy”, “vort max” (or “vorticity maximum”), “pocket of cold air” (or “pocket of energy”), “upper level disturbance”, “upper-level energy”, or just “shortwave” are some of the slang terms for waves with a length of less than 3,700 miles (6,000 km).
They are embedded within the longwaves. Unlike the slow movement of longwaves, shortwaves move east (downstream) on average of 23 mph (20 kts, 37 km/h) in summer and 35 mph (30 kts, 55 km/h) in winter. This motion causes longwaves to distort and change shape such as deepening longwave troughs and flattening longwave ridges.
Due to their variety of sizes, it can be difficult to discern shortwave embedded within a longwave by looking at a static map. One often needs to see looping images of the wave patterns to determine the difference between them.
Shortwaves, embedded within longwaves, are also the chief instigator of episodes of precipitation. Main precipitation bands will be typically localized near the short wave as it passes overhead.
Below is an example of a 500 mb chart. The height contours are in black. The brown arrows indicate the direction of airflow. The large red dashed lines represent the location of the long wave troughs.
The shorter blue dashed lines represent the location of the more prominent shortwaves. (There are more short waves than indicated.) The green areas represent precipitation totals. The areas of precipitation are mainly associated with shortwaves as they pass through longwaves. Like railroad cars on a train track, shortwaves will generally follow height contours.
Forecast Discussion
- Rain and snow expected today with cooler temperatures A cold front is pushing through Western Lower Michigan as of 300am...pushing into the Highway 131 corridor. Colder air is obviously situated behind the front with some synoptic scale precipitation over Northern Wisconsin. Much of this precipitation is in the form of snow to the west and northwest of Green Bay. This precipitation will work our direction early this morning and swing through our area today. We are expecting a rain and snow mix over a fair amount of the forecast area, especially from Grand Rapids off to the north into Central Lower Michigan. Models are indicating the potential for a couple inches of wet snow towards Ludington and Baldwin. We are not expecting any impacts given warmer ground and marginal air temperatures in the 30s. We are expecting accumulations to be more on the order of trace amounts to maybe an inch. Cannot rule out a 2 inch total on the high ground near Tustin and Dighton. Overall a blustery damp day with a good deal of cloud cover hanging in across the area. Thinking we may see some wind gusts this afternoon increase towards advisory levels, but expecting most gusts to remain in the 30-40 mph range. - Mid week upper trough to bring colder weather A strong upper trough will plow into the area Tuesday night and remain overhead into Thursday. The trough will be led by a cold front at the surface that moves into the area on Tuesday. The front will largely be dry on Tuesday, but some light rain is possible. Better chances for precipitation will come Tuesday night into Wednesday when post frontal precipitation breaks out. Rain and snow is forecast as 850mb dip below Zero C. Air that is quite cold for this time of year flows in with the upper trough. 850mb temps dip to around -15C Wednesday night. We will likely see some lake effect snow develop with some marginal moisture in place to go along with delta T`s towards 20C. Another windy period Monday night into Tuesday with strong winds just off the deck. We will need to look at wind advisory potential once again, but it looks like for now we may be just shy again. - Some model disparity towards the end of the week We are looking largely dry to end the week. The operational GFS and ECMWF are both indicating a weak shortwave moving through the area in northwest flow Friday night into Saturday. There are timing differences at this point and the models are not kicking out much QPF. We will watch this time frame, but overall it does not look impactful.
Check this out! A very cold week is upon us! Enjoy!
– Upper low brings snow showers on Thursday
Cold upper low moves south on Wednesday and is centered over
Michigan on Thursday with some diurnal enhancement of showers.
Looks plenty cold enough for snow showers with possible snow
pellets and graupel for any stronger updrafts, which could be
heavy enough to coat the ground.
Lol! So one cold day on Thursday is a whole week now??
U of M is rolling!
Forget golf and embrace this great cold stretch of Spring weather! More of the same later this week!
Cold streak?!?!??!
95 percent of the 10 day is in the 60’s!! DELUSIONAL!!!
https://weather.com/weather/tenday/l/b4ea0280869baa46799dc75eacef8904785ec43ad2f6fb098355fbc208a55e2c
I believe it’s snowing or sheeting out in my area nice Spring Sunday we just ordered a pizza great stay in day ….INDY
Yes and it is snowing up here also! I love it!
Perfect Rocky day outside today!! Windy, Rainy, cold and crappy!! Hopefully he’s sitting out on his back deck today enjoying it! Very few of these perfect days for him!!
Great day, I bundled up and went hiking! Just awesome!
Currently 35* degrees with clouds in my area very nice Spring day out there lol….Mackinac bridge is getting heavy snow now …INDY
Definitely tell when our plane was over Michigan yesterday i sad to my wife look how brown everything is and no leafs on the trees yet we have a lot of Spring growing to do here lol….Let’s Go Blue!! Have a super Sunday …INDY
Picked up 0.04″ of rain overnight. The temperature has been falling all night long and the current temperature of 40 is the low for the day so far. At this time there is light rain fall with that reading of 40. At this time the March mean at Grand Rapids is 40.8 and GR is on track for one of the warmer March’s in recorded history.
Slim