On May 6, 1955, a revolution that continues to this day began with little fanfare: the first daily weather forecasts made by a computer were issued. This was the result of nearly a year of collaborative effort between the United States Weather Bureau, the Air Force and the Navy in what was called the Joint Numerical Weather Prediction Unit, or JNWPU.

Formed in July 1954, the JNWPU was charged with applying emerging computer technology to the production of weather forecasts. The numerical forecasts issued during its first couple of years were not nearly as good as the forecasts being prepared manually with just pencil, paper and theory by experienced meteorologists at the Weather Bureau. Many academic meteorologists thought it was folly to pursue numerical weather prediction, and they were not afraid to express their opinions on the matter. But by 1958 the forecasts began to show steady improvement in skill.

Fueled by improved understanding of the atmosphere, better observations (many of which are supplied by satellites that did not exist in any form in 1955), and incredible increases in computer power, the science of numerical weather prediction has developed into an enterprise that now informs or supports a large part of the U.S. economy.

From the seven-day advance warning of Hurricane Sandy to our December blizzard this past year when schools were canceled before a single snowflake fell, we are indeed living in revolutionary times.

We should be proud of the fact that substantial contributions to that revolution have been made at UW-Madison for more than 60 years.

The scientific era of weather modification took hold in the 1940s and ’50s with the advent of cloud-seeding experiments. In cloud seeding, airplanes drop particles of dry ice or silver iodide into clouds with temperatures below freezing. These particles are very effective in generating ice particles, with the hope of increasing the amount of rainfall or snowfall.

However, progress in cloud seeding has been slow as the processes are poorly understood. Not only that, these experiments aren’t reproducible in the sense that we can never really know if a seeded cloud would not have precipitated on its own, without assistance.

Farmers have long sought a way to suppress hail. One hailstorm can destroy a year’s crops in a few minutes. Cloud seeding during the early stages of cumulonimbus development is thought to encourage a reduction in hail damage by keeping hailstone sizes small, but again, the results have been mixed.

Another active area of weather modification has been fog dispersal. Fog can shut down an airport for hours, causing delays with negative economic impact. Like clouds, fog can be seeded with materials that cause the water droplets in fog to turn into ice, which then precipitates out, dispersing the fog. While a practice at many airports worldwide, it is impractical to apply over large regions.

Humans have changed the atmosphere in many ways. These changes usually come about as unintended byproducts of modern civilization. So far, humans have been more effective at modifying weather and climate by mistake than by design.

Milwaukee recorded 15.19 inches of liquid-equivalent precipitation, just outpacing the prior record of 15.08 inches set in 1976. Madison recorded 13.45 inches of liquid equivalent through April 24, breaking the former record of 13.30 inches set in 1973.

It does appear that the faucet will be turned down at least for the next week or so, though occasional showery days still seem to be in the near future.

What is causing the persistent snowy/rainy pattern that we have endured these past couple of months? The answer to such questions regarding the behavior of the atmosphere is not often easy to uncover, and a lot of effort must be spent after the fact looking for explanations.

One of the most satisfying aspects of studying atmospheric science is that interesting questions come up all the time. It is easy to remain motivated to keep thinking.

Pursuing such questions invariably leads to new insights about a variety of other weather phenomena that were not originally part of the research project.

When you hear people talk about the importance of “basic research,” this is what they mean: that by pursuing question A, a curious mind will stumble upon answer B and that answer may lead to the development of brand new insights about nature. Study of this wet beginning to 2013 will almost surely yield unintended new insights as well.

Through April 17, Madison had recorded 12.95 inches of liquid equivalent precipitation for the calendar year. That means that 2013 has gotten off to the third wettest start in Madison history. Milwaukee has received 13.15 inches of liquid equivalent this year, also making it the third wettest start to a year.

Both cities trail only 1876 and 1974 in the record books.

As far as temperature goes, Madison is running 4 degrees below normal for April. This is in the wake of a February and March that were 2 degrees and

7.4 degrees colder than normal. A similar set of circumstances has affected Milwaukee where February was 1.8 degrees below normal and March was 5 degrees below the average.

The bottom line is, we are well overdue for the arrival of warmth.

Even Major League Baseball has suffered from the incessant rain, posting an unusually large number of rained-out games in April (13 so far) in an era when the rainout is less likely because of domed stadiums.

The good news is the medium-range forecasts issued by the National Center for Environmental Prediction suggest warmth is coming. It appears that by the end of this week we will finally be looking at bona fide warm spring days.

Suspicions remained unconfirmed until World War II. During major U.S. air raids against Japan, the B-29 airplanes flew from east to west at altitudes of 10 kilometers, where they encountered a strong stream of westerly winds that slowed or even stopped the planes in mid-air. There were also balloon observations made in the early to mid-1920s by Wasaburo Ooishi, the first director of Japan’s upper-air observatory, that suggested these fast moving winds.

Today’s weather reports often discuss the position of the jet stream. The jet stream position is strongly tied to the southern edge of the dome of cold air centered on the North Pole. During the depths of winter, that cold dome expands considerably, extending nearly to the Gulf of Mexico. As the winter ends and spring approaches, the hemisphere begins to warm up and the cold dome shrinks dramatically. Its southern edge moves to central Canada by early summer.

The jet stream is associated with vigorous upward and downward vertical motions. The upward vertical motions are instrumental in producing thunderstorms. Thus, when the jet stream migrates northward as the weather warms in spring/summer, so does the greatest concentration of severe weather outbreaks. That season is heading our way, denoted by designating this week as Tornado and Severe Weather Awareness Week, with a drill day planned from 1 to 2 pm. on Thursday.

That means that consecutive months of March (2012 and 2013) had a 23.5-degree difference in their average daily temperatures — surely some sort of record for the same month in consecutive years (we are still trying to verify if this is, in fact, a record).

Leaving the issue of records aside, it is interesting to note the local departure from normal is not necessarily in line with the departure over the whole Northern Hemisphere. In fact, while we were basking in warmth last March, the hemisphere was colder than average, and while we were shivering this March, the hemisphere was warmer than average. Little consolation for those tired of winter.

However, it must be noted that the transition from March to April in Madison is accompanied by the single biggest one-month increase in average daily temperature of the year (from 34 degrees in March to 46.6 degrees in April). If April unfolds more or less normally, the inevitable warming will not only be especially welcome but will seem especially strong.

Atmospheric rivers are apparent in satellite images and are often in the vicinity of fronts over the oceans. They transport large amounts of water. Atmospheric rivers that transport water vapor from Hawaii to North America are sometimes nicknamed the “pineapple express.”

While these atmospheric rivers are made of water in the gas form, or water vapor, they can carry as much water as a dozen Mississippi Rivers. The features can transport water into storms and result in extreme precipitation events that cause severe flooding in western coastal regions of the world, including the West Coast of North America.

In early December 2012, San Francisco received about 10 inches of rain from water vapor transported across the Pacific Ocean by one of these rivers of vapor. While some of these events lead to flooding and mud slides, most precipitation events simply provide beneficial precipitation important to a region’s water supply.

Because of these features’ importance to the water supply of a region, their movements are important to follow and forecast. They are monitored using satellite measurements, aircraft reconnaissance and a new set of instruments along the coast of California. These observations, combined with better numerical modeling, will likely improve forecasts that eventually will help improve water management.

Meteorologically, we can define the first day of spring as when, based on at least 30 years of observations, the probability is greater than 50 percent that should some sort of precipitation fall, it will be rain rather than snow. That date has also passed. For southern Wisconsin, that calendar day is around March 16.

Some people define spring as the first day they see a robin. We’ve seen flocks of robins in Madison this month, so that day also has passed.

While various definitions of spring indicate it has arrived, it sure seems wintry. From a climate perspective, it is not common to have this much snow on the ground after the vernal equinox. The outlook for the coming week includes below-normal temperatures.

Springtime is generally considered to be the three months of March, April and May. The official National Oceanic and Atmospheric Administration, or NOAA, outlook for spring is for warmer-than-normal weather across most of the U.S. There will have to be some warm months ahead to have that happen in Madison.

On a related note: NOAA cautions that the melting of late-season snow may cause minor to moderate flooding in the upper Mississippi River basin, including southern Wisconsin.

In those 42 days, Madison has had 30 days on which at least some snow has fallen.  This is a truly remarkable period for frequency of snowfall.  Aside from the regularity of snowfall in February and March, our seasonal total of 63.2 inches (as of March 14) ranks 14th all-time in Madison for seasonal snowfall.  In fact, we only need an additional 7.5 inches to break into the top 10 snowiest winters of all time as the 70.7 inches that fell in 1897-98 currently holds the No. 10 spot in the record books.

Our guess is that this is rather unlikely — but not impossible — as the longer-range forecasts are not suggesting any really dramatic warm-up through late March, well after the Spring equinox that falls on March 20 this year.

This has been a nearly exact opposite of last March when, by the 14th, we were experiencing temperatures in the high 70s (it was 78 on March 14 last year!).  March 15, 2012 was our first in a string of five days (over a single week) with temperatures over 80F.  What a difference a year makes.

The field corn and soybeans crops of the Midwest have been particularly hard hit. Water systems throughout the country have been affected by the lack of moisture. Low water levels in parts of the Mississippi have a negative effect on trade and commerce. Even with this dry weather, some have noted the uncomfortable humidity. To address how this can be, we need to first define a drought.

There are several definitions of drought, but in general there are three types. A meteorological drought is any substantial and prolonged lack of rainfall over a period of time in a given region. A hydrological drought is a deficiency in surface or subsurface water supplies. An agriculture drought exists when there is not enough soil moisture to meet the needs of a crop at a particular time.

There can be many water vapor molecules in the air, which increases the humidity of the air, but if those water molecules in the gas phase do not condense to form clouds that eventually grow to raindrop-sized particles, it will not rain. The humid air near the ground must rise, which will cause clouds to form and possibly precipitate. Without that air rising, there can be a lot of uncomfortable humidity while in a drought condition.