2:30 PM | Global sea ice areal extent running at slightly above-normal levels

[Yellow line represents the year-to-date Southern Hemisphere sea ice areal extent compared to all other years going back to 1979; data courtesy University of Illinois "cryosphere"; NOAA/NCEP Snow and Ice Data Center]

Discussion

Overall Summary

Southern Hemisphere sea ice areal extent continues to run near record high levels in the satellite data era (circled area above) for this time of year in records going back to 1979 whereas the Northern Hemisphere continues to run near record low levels in the same comparison time period (circled area on bottom plot). Overall, the global sea ice areal extent is currently running slightly above-normal at just under half a million square kilometers above the 1979-2008 mean (below).

[red line represents global sea ice areal extent compared to the 1979-2008 normal as represented by the “zero” line; data courtesy University of Illinois "cryosphere"; NOAA/NCEP Snow and Ice Data Center]

Southern Hemisphere Sea Ice

The rather remarkable period of consistently higher-than-normal sea ice areal extent in this part of the world actually began a few years ago. Back in 2011, the southern hemisphere sea ice areal extent was still at below-normal levels, but it has surged in recent years to the current 1.2 million square kilometers above the 1979-2008 mean.

Northern Hemisphere Sea Ice

The northern hemisphere sea ice areal extent is still below-normal relative to all years going back to 1979 although it is well above the lowest point set during 2012 and even above levels seen earlier this year. The northern hemisphere sea ice areal extent is currently 0.8 million square kilometers below-normal using the base period of 1979-2008 for comparison. The northern hemisphere sea ice areal extent has leveled off in the past 10 years or so at below-normal levels after dropping consistently from the mid 1990’s to the middle of the last decade. In the time period before the mid 1990’s, the sea ice areal extent was generally above-normal dating back to 1979.

The directional shift in the sea ice areal extent trendline that developed during the mid 1990’s in the northern hemisphere correlates quite well with a northern Atlantic Ocean sea surface temperature cycle that is tracked by meteorologists through an index called the Atlantic Multidecadal Oscillation (AMO). Indeed, Atlantic Ocean sea surface temperature anomalies play a critical role in the overall northern hemisphere sea ice areal extent. The AMO index flipped in phase during the mid 1990’s from negative (cold) to positive (warm) and the sea ice areal extent trendline changed direction right around that point in time.

The Atlantic Ocean is just recently showing signs of a long-term temperature phase shift back to cold and if that trend continues over the next couple of years then the northern hemisphere sea ice areal extent is quite likely to return to the above-normal levels seen prior to the mid 1990’s. (Click here for more information on the potential significant temperature phase shift in the Atlantic Ocean: http://vencoreweather.com/2015/03/22/1230-pm-the-atlantic-ocean-is-showing-signs-of-a-possible-significant-long-term-shift-in-temperatures-from-warm-to-cold/).

[Yellow line represents the year-to-date Northern Hemisphere sea ice areal extent compared to all other years going back to 1979; data courtesy University of Illinois "cryosphere"; NOAA/NCEP Snow and Ice Data Center]

Paul Dorian

Vencore, Inc.

1:10 PM | Colder-than-normal pattern to set up in eastern two-thirds of nation during the second half of April

[Today's 500 millibar pattern, map courtesy Penn State eWall, NOAA]

Discussion

Overview

So far the month of April has been warmer-than-normal in DC (+3.5°), Philly (+1.3°) and at Central Park (+1.4°) in New York City, but the overall weather pattern is about to undergo a significant change in the eastern two-thirds of the nation as we progress through the second half of April. In fact, in many ways, the upcoming weather pattern in the upper atmosphere will resemble the one that endured throughout much of the winter season. The threat of snow will even make a return to the Northeast US as we progress through the latter stages of April - at least in some of the higher elevation interior locations.

[Next Wednesday's forecasted 500 millibar pattern, map courtesy Penn State eWall, NOAA]

500 millibar pattern reversal

Currently, there is strong high pressure ridging across the eastern US (top, orange region) and a deep trough of low pressure in the interior western US (top, blue region). As a result, the eastern US is currently enjoying rather mild conditions whereas snow is falling in the central Rockies including in the city of Denver and several feet of the white stuff is possible just to the west of Denver during the next couple of days. All of this is about to change.

According to the latest GFS Ensemble computer model forecast, the ridge in the eastern US will be replaced by deep a low pressure trough (above, blue region) by the middle of next week and a strong high pressure ridge will form across western Canada (above, orange region). This type of 500 millibar pattern existed during much of the winter season and it promotes the transport of colder-than-normal air from Canada into the US. During this transitional period in the overall upper atmosphere pattern, there is likely to be a significant rain event in the Mid-Atlantic region at the beginning of next week and then colder air is destined to follow later in the week.

[North Atlantic Oscillation index (current and past values in black, forecasted index values in red), map courtesy NOAA]

North Atlantic Oscillation index

In addition to the GFS Ensemble forecast, there is corroborating evidence that colder-than-normal weather is coming to the eastern US. An index known as the North Atlantic Oscillation (NAO) is forecasted to flip in signs from positive-to-negative as we progress through the latter stages of April. The current value of the NAO index (above, in black) is clearly in positive territory, but it is forecasted to drop sharply during the next week or so (above, in red). A negative NAO index value this time of year generally supports the idea that colder–than-normal air can be transported from Canada into the central and eastern US. The latest 2-meter temperature anomaly forecast (below) by the GFS computer forecast model for the 5-day period of April 26 to May 1st shows the widespread extent of the coming colder-than-normal weather pattern.

[00Z GFS 2-meter temperature anomaly forecast map for the 5-day period of April 26 - May 01, map courtesy Weather Bell Analytics]

1:40 PM | April can be the cruelest month

[12Z GFS 10-day forecast map for 500 millibar height anomalies (blues=low pressure trough, oranges=high pressure ridge); map courtesy "tropicaltidbits.com", NOAA]

Discussion

Despite the chill for the past two days in the I-95 corridor, so far the month of April has actually been warmer-than-normal in DC (+3.2° at Dulles Airport), Philly (+2.1°) and at Central Park (+1.5°) in New York City. In addition, tomorrow will feature a dramatic warm up throughout the Mid-Atlantic region and it should stay relatively mild though much of next week. However, on a longer-term basis, it appears that we are definitely not done with the colder-than-normal air yet as there will be a pattern change later in the month.

A deep trough of low pressure (blue area on forecast map above) will form in the eastern US in 10 days or so according to the most recent GFS computer forecast model run and this will produce a pattern similar to that of much of the winter season which generated below-normal temperatures in the eastern part of the nation while much of the western US is relatively warm. In fact, going a few days farther into the future, the latest GFS model forecast for 14 days from now (below) features a blob of colder-than-normal temperatures (blue) in the Northeast US with much of the interior western US warmer-than-normal (oranges).

Enjoy the warmth that returns tomorrow and lasts well into next week as April can be a cruel month and change on a dime in the Northeast US.

[12Z GFS 14-day forecast map for 2-meter temperature anomalies (blues=colder-than-normal, oranges=warmer-than-normal); map courtesy "tropicaltidbits.com", NOAA]

2:30 PM | Baseball is back and so is the "Home Run Weather" app!

Discussion

It has long been contemplated that weather conditions have an effect on the distance a baseball can travel. More home runs are seemingly hit on hot days or on days with the wind blowing out.

Who can forget the many games at Wrigley Field that have featured numerous home runs as the wind raced out towards Waveland Avenue? Mike Schmidt cranked four home runs on just such a day at Wrigley Field in April of 1976. That game featured nine home runs and 34 total runs and a wind blowing out strongly ahead of a cold front. Not surprisingly, most of the games with four home runs hit by an individual player have occurred with temperatures of at least 80 degrees or with a strong wind blowing out. Conversely, most people would agree that fewer home runs are hit on cold days or with the wind blowing in. The old Candlestick Park in San Francisco frequently offered such weather.

The distance that a baseball travels is indeed impacted by atmospheric conditions. In general, the less dense the air is, the farther a baseball can travel. Humidity plays a crucial role in air density. Air with higher humidity is actually less dense than drier air. This may be contrary to perception and many baseball fans have no doubt heard baseball announcers incorrectly use the phrase “heavy humid air” on a hot summer night. Dry air is mostly comprised of diatomic oxygen and nitrogen (i.e. O2 and N2) whereas water vapor (H2O) is composed of one oxygen atom and two hydrogen atoms and the moist air has a lower overall atomic mass than dry air. Thus, at a constant temperature, the more water vapor that displaces the other gases, the less dense the air will become.

Additionally, hot air is less dense than cold air and higher altitude air is less dense than air at sea level. It is for this reason that so many home runs were hit in Colorado before the humidor was put into place. The elevated humidity in the humidor that stores baseballs for the Rockies home games effectively reduces the distance that a ball will travel in multiple ways: 1) by adding slightly to its weight through absorption of water, 2) by causing the size of the ball to increase slightly which increases air drag and 3) by reducing its “bounciness” factor.

Utilizing sophisticated math and physics, meteorologists and software engineers at Vencore, Inc. (formerly The SI Organization, Inc.) investigated this topic which mixes science and baseball. And the results of their efforts are available in a free, real-time baseball weather application called “Home Run Weather”. Developed for the iPhone and Android devices, the app relates live temperature, atmospheric pressure, humidity, field orientation, wind direction, wind speed and the drag coefficient of a baseball to the user to determine if local weather conditions, for any big league park, are favorable for home runs being hit. Twenty-four hour forecasts are available in addition to live weather.

Two approaches were combined to arrive at a “home run favorability” index, which the app displays on a scale of 0 to 10 (least-to-most favorable). The first approach was to analyze actual weather conditions and home run data over several seasons (Citizens Bank Park was chosen as the venue for this study). The second approach uses a theoretical, physics-based model that determines the distance a ball will travel based on the temperature, relative humidity and atmospheric pressure.

The Citizens Bank Park study yielded some interesting, but perhaps not too surprising, findings. First, temperatures and dew points had a clear trend line relationship with home runs, as generally more home runs were hit in hot and humid air than colder, less-humid air. It was also found that 13-percent more home runs were hit when the wind was blowing out than other wind conditions. Additionally, 6-percent more home runs were hit in the daytime as compared to nighttime games.

A full major league season of testing on the app index produced very encouraging results with respect to the average number of home runs hit per game. The low home run favorability index values (0-3) had an average of 1.38 home runs per game for the full season. The moderate index values (4-7) had an average of 1.95. And the high values (8-10) had an average of 2.47 home runs per game. In addition, the home run favorability index correlated very well with average total runs scored per game. The low home run favorability index values (0-3) had an average of 7.07 total runs per game for the season. The moderate index values (4-7) had an average of 8.08. And the high values (8-10) had an average of 9.45 total runs per game.

Whether you're a fan at the park who's interested in a home run forecast, a spirited fantasy owner or baseball analyst, the “Home Run Weather” app should provide some useful information and conversational material. For more information, visit the "Home Run Weather" page at http://vencoreweather.com/homerun/.

10:45 AM | *April pattern change is likely to bring more sustained warmth to the Mid-Atlantic, rains to California and the Southwest US, and a sharp increase in severe weather to the Plains/Midwest/Ohio Valley*

[00Z GFS Ensemble run forecast maps of 500 millibar height anomalies for tomorrow (left) and April 7th (right); map courtesy Penn State e-Wall, NOAA]

Discussion

Overview The end of winter in the Mid-Atlantic region may be finally at hand. For several weeks now, the overall upper-level pattern has featured a ridge of high pressure along the west coast of North America and a trough of low pressure in the northeastern US. This pattern has brought about sustained colder-than-normal weather in the Mid-Atlantic region for the past few months, warmer and drier-than-normal weather for the western US, and it has helped to suppress severe weather activity in the Plains, Midwest and Ohio Valley. In fact, the tornado season is off to an historically low start as we approach the end of March (circled area on plot at bottom). All of this should begin to change over the next week or so as there will likely be a flip in the overall pattern with an upper-level trough forming in the western US and an upper-level ridge developing in the northeastern part of the country. Indeed, this upcoming upper-level pattern flip will have weather implications across the entire nation for much of the spring season.

Mid-Atlantic warm up The latest GFS Ensemble computer forecast model run for the 500 millibar height anomalies (above) shows a reversal of positions for the ridge and trough in the US between tomorrow and a week later on April 7th. Other computer forecast models generally agree with this potential pattern flip including the European (not shown) and Canadian (below). This change in positions of upper-level features will have serious implications on the overall flow of air across the entire US with an increasing southwesterly flow pumping milder air in the Mid-Atlantic region. This southwesterly flow of air should result in above-normal temperatures on a more sustained basis than recent weeks in the Mid-Atlantic region beginning in the next week or so. January, February and March were colder-than-normal months in the Mid-Atlantic region, but April and May have good chances to be above-normal.

[00Z Canadian model forecast map of 500 millibar height anomalies averaged out for the 7-10 day time period ending on April 7th; map courtesy Penn State e-Wall]

California drought The flip of upper-level systems from ridge-to-trough out in the western US is quite likely going to open the door for more rainfall in the Southwest US and this should include California which has been suffering through a long-term drought. The upcoming change in the overall weather pattern should allow for more eastward penetration of Pacific Ocean moisture into the western US and this should help alleviate the drought situation during much of the spring season. (San Francisco is suffering through its driest "January/February/March" time periods on record).

Threat for severe weather/tornadoes Finally, in addition to the warm up in the Mid-Atlantic region and the potential additional rainfall in the southwestern US, the increasing southwesterly flow of air in the eastern half of the nation will pump moist air northward from the Gulf of Mexico into the Plains, Midwest and Ohio Valley. This influx of moist air has been one important missing ingredient so far this spring in terms of the development of severe weather and tornadoes. Unfortunately, the addition of more humid and warmer air into the Plains, Midwest and Ohio Valley will likely result in a quick ramp up of severe weather and tornado activity that could take us from early-to-mid April into the month of May.

[Tornado season is off to an historically low start through the first three months of the year; courtesy NOAA]

12:30 PM | The Atlantic Ocean is showing signs of a possible significant long-term shift in temperatures from warm-to-cold

[Sea Surface Temperature Anomaly comparison chart between July 2014 and today; courtesy NOAA]

Overview

In addition to solar cycles, temperature cycles in the planet’s oceans play critical roles in climate and on the ever-changing distribution of global sea ice. Oceanic temperature cycles are often quite long-lasting and a warm or cold phase can persist for two or three decades at a time. The Atlantic Ocean experienced a cold phase from the early 1960’s to the mid 1990’s at which time it flipped to a warm phase and that has continued for the most part ever since. The current warm phase; however, is now showing signs of a possible long-term shift back to colder-than-normal sea surface temperatures (SST) and this could have serious implications on the climate and sea ice areal extent in the Northern Hemisphere.

Recent temperature trends in the Atlantic Ocean

Sea surface temperatures have dropped considerably during the past eight months or so in much of the northern Atlantic Ocean. The comparison chart above of SST anomalies between July 2014 (top portion) and today (bottom portion) shows a big drop in temperatures across much of the northern Atlantic Ocean. First, the rather limited colder-than-normal (blue) regions from July 2014 have increased noticeably in areal extent during the past eight months. Second, the well above normal waters (orange) of July 2014 that existed east of Greenland have cooled off dramatically during this time period to only slightly above normal (yellow) and there has even been a switch from well above normal (orange) to below normal (blue) in this area east of Greenland. Notice also that most of warm pockets of water off the Northeast US coastline in July 2014 (orange) have persisted for the most part during this general cool-down in the northern Atlantic Ocean during the past eight months; however, that may be about to change.

Longer-term trends in the Atlantic Ocean

On a longer time scale, there is supporting evidence from the National Oceanographic Data Center that something significant is indeed occurring in the Atlantic Ocean. Since around 2006/2007, there has been a definitive downward trend in “monthly heat content anomaly” in the top 700 meters of the northern Atlantic Ocean (below). The heat content in this part of the Atlantic Ocean ramped up rather sharply beginning around the middle 1990’s (first arrow) and seemingly peaked during 2006/2007 (second arrow).

[Monthly heat content anomaly trend in the top 700 meters of the northern Atlantic Ocean; courtesy National Oceanographic Data Center]

Atlantic Multidecadal Oscillation (AMO)

One way meteorologists can monitor sea surface temperature patterns in the North Atlantic Ocean is through an index value known as the Atlantic Multidecadal Oscillation (AMO). The monthly values for the AMO index are shown in the plot below for the period of 1856-2013 where positive values (reds) represent warmer-than-normal time periods and negative values (blues) indicate cold phases. Sea surface temperature cycles have tended to last for two or three decades at a time before phase changes take place. Since late last summer, the AMO index has actually dropped rather consistently from +0.355 to a now barely positive value of +0.016 (not shown in plot) providing supporting evidence that a cool-down is indeed occurring in recent months in the Atlantic Ocean.

[Atlantic Multidecadel Oscillation monthly index values where red indicates warm phases and blue cold phases; courtesy NOAA]

Model Forecast for Atlantic Ocean sea surface temperatures

One indication that this downward trend in Atlantic Ocean sea surface temperatures may continue comes from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). JAMSTEC’s global seasonal forecasting of sea surface temperature anomalies has a pretty good track record and its most recent long-range forecast (below) suggests there will be a fairly widespread area of colder-than-normal water in the northern Atlantic Ocean by the fall of 2015 (blue regions) and this includes the noticeable disappearance of those very warm pockets that are currently situated in the western Atlantic near the US coastline.

[JAMSTEC model forecast of sea surface temperature anomalies for fall season 2015; courtesy Japan Agency for Marine-Earth Science and Technology]

Ramifications on Northern Hemisphere Sea Ice Areal Extent

If the Atlantic Ocean is indeed slipping back into a colder-than-normal phase (i.e., negative AMO) then this would quite likely have a significant impact on Northern Hemisphere (NH) sea ice areal extent. The NH sea ice areal extent was generally at above-normal levels before the middle 1990’s (arrow in plot below) which is when the Atlantic Ocean temperature phase change took place from cold-to-warm. Once the warm phase of the Atlantic Ocean became established in the late 1990's, the NH sea ice areal extent trended sharply downward from positive levels into well below-normal territory. In recent years, there has been a jagged, but generally sideways trend in NH sea ice areal extent at those well below normal levels. However, if these recent signs of a possible long-term Atlantic Ocean temperature phase change from warm-to-cold are "real and sustained" (and sometimes there are false starts), then the NH sea ice areal extent will very likely return to above-normal levels in the not too distant future - just as it was during the last cold phase pre-mid 1990’s.

[Northern Hemisphere sea ice areal extent; courtesy University of Illinois "cryosphere", NOAA]

Ramifications on Climate

The impact on climate from a potential Atlantic Ocean temperature shift of warm-to-cold are less clear as the all-important Pacific Ocean would have to be factored into the equation. The temperature cycles in the Pacific Ocean are critically important to weather and climate across the US and elsewhere and will have to be monitored in the years to come. Certainly, the last cold phase of the Atlantic Ocean produced numerous cold winters in the Northeast US such as during the latter part of the 1960's and also in the 1970's. If the eastern Pacific Ocean remains warmer-than-normal for next winter season as it was for this year and the western Atlantic Ocean cools down as predicted, this could very well set the stage for another colder-than-normal winter in the Northeast US for 2015-2016.

Paul Dorian

Vencore, Inc.

9:30 AM | *Winter-like pattern to resume after "spring break"*

Discussion

Overview This break in our recent cold and stormy weather pattern will continue to provide us with glimpses of spring-like warmth over the next 7 days or so, but the signs for a return to a winter-like pattern in the Northeast US are rather convincing. There are numerous signals that point to a period of colder-than-normal weather in the Northeast US for the last third of March and the beginning third of April (roughly March 18-April 10) and it is quite likely to include more threats of snow. These signals that suggest there will be a return to a winter-like pattern are described below and involve such things as the Madden Julian Oscillation, stratospheric warming, 500 millibar height anomalies, and the Arctic Oscillation index.

Madden Julian Oscillation (MJO) The MJO is a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days. It is a large-scale coupling between atmospheric circulation and tropical deep convection. The MJO has wide ranging impacts on the patterns of tropical and extratropical precipitation, atmospheric circulation, and surface temperature around the global tropics and subtropics. Furthermore, the MJO influences both precipitation and surface temperature patterns across the US. Specifically, one significant impact of the MJO in the U.S. during the northern hemisphere winter is an increase in the frequency and intensity of cold air outbreaks across the central and eastern US.

[European model forecast of the MJO index through March 23rd; courtesy NOAA]

MJO Phases Research has found that the location of the MJO, or phase, is linked with certain temperature and precipitation patterns around the world. The MJO phase diagram (above) illustrates the recent and forecasted progression of the MJO index through different phases which generally coincide with locations along the equator around the globe. When the index is within the center circle, the MJO is considered weak, meaning it is difficult to discern. Outside of this circle, the index is stronger and will usually move in a counter-clockwise direction as the MJO moves from west to east. The very latest European computer forecast model predicts an increasingly strong MJO index that will propagate through “phase 6” into “phase 7” on its way to “phase 8” over the next few weeks (follow green line in figure above in a counter-clockwise fashion). Phases 7 and 8 for the MJO index for this time of year (i.e., March/April/May) typically signal colder-than-normal temperatures in the northeastern U.S. (see circled “blue” regions below in "phases 7 and 8" temperature anomaly charts).

[US temperature anomalies for different phases of the MJO index during the period of March/April/May; courtesy NOAA]

Sudden Stratospheric Warming (SSW) Another way to monitor the potential for Arctic air outbreaks in the northeastern U.S. is to follow what is happening in the stratosphere over the polar region of the northern hemisphere. Sudden stratospheric warming (SSW) events in the region of the North Pole have been found to set off a chain of events in the atmosphere that ultimately lead to Arctic air outbreaks from central Canada into the northeastern U.S. Indeed, there is reason to believe that there will be a significant stratospheric warming event during the next couple of weeks over the North Pole that could contribute to a return of our colder-than-normal temperature pattern in the northeastern U.S. as we progress through the latter part of March and into the month of April. The current stratospheric temperature pattern (at 10 millibars) and the 10-day forecast are shown below and they show an impressive area of stratospheric warming closing in on the North Pole later this month with the typical "polar-based" cold vortex getting displaced towards Asia.

[Temperature analysis at 10 millibars (stratosphere), current and 10-day forecast; courtesy NOAA]

500 millibar height anomalies The 500 millibar height anomaly forecast (below) for 10 days from now from the 06Z GFS Ensemble run indicates strong ridging (oranges) will re-develop in western Canada at the same time troughs of low pressure (blue) will form in the northeastern US and in the North Pacific region just to the south of Alaska. This type of upper air pattern usually leads to multiple Arctic air mass incursions into the northern US from northern Canada and, in fact, was in place for much of this winter season. This forecast map also suggests that the upper-level winds at 500 millibars – which tend to follow the height anomaly lines - could actually bring air directly from the North Pole into the northeastern US by the latter part of March. In addition, there are signs for “blocking” high pressure to form near Greenland at this same time period (oranges) and that tends to help keep cold air sustained in the northeastern US for a lengthy period of time.

[06Z GFS Ensemble 500 mb height anomaly forecast map for March 20th; map courtesy "tropicaltidbits.com", NOAA]

Arctic Oscillation index High-latitude blocking can be tracked by meteorologists through indices known as the Arctic Oscillation (AO) and its closely-related cousin called the North Atlantic Oscillation (NAO). When the AO is positive, for example, surface pressure is low in the polar region and this helps the mid-latitude jet stream to blow strongly and consistently from west-to-east keeping Arctic air locked up in the polar region. When the AO index is negative, there tends to be high pressure in the polar regions (i.e., “high-latitude blocking”), weaker zonal winds, and greater movement of polar air into the middle latitudes. The forecast of the AO index (red line on plot below) suggests there will be a plunge from the current strongly positive value to well into negative territory by later this month which supports the theory that cold air will be sustained in the northeastern US as an upper-level blocking pattern develops.

[Observed (black) and forecast (red) of the Arctic Oscillation index; courtesy NOAA]

Paul Dorian Vencore, Inc.

10:00 AM | *The cold is getting old, but it just won't fold*

[NOAA CFSv2 45-day temperature anomaly forecast; map courtesy Weather Bell Analytics at weatherbell.com, NOAA]

Discussion

Not only will February turn out to be one of the coldest February’s ever in much of the Northeast US and Upper Midwest, but it will likely turn out to be one of the coldest months ever in many locations. For example, Bridgeport, CT, Islip, NY and Cleveland, OH are all on pace for their coldest month ever; JFK and LaGuardia Airports in New York City are likely to join with Boston, MA and end up in the top two or three for their coldest month ever recorded.

In the I-95 corridor region of DC, Philly and New York City, temperatures have averaged around 10 degrees below normal through February 24th, and there is certainly no reason to believe these numbers will change much over the remainder of the month which will continue to average well-below normal. Philly is currently on pace for its third coldest February ever and likely will end up in the top ten for coldest months ever. All indications are that this colder-than-normal weather pattern in the Northeast US will continue right through March and perhaps even into April despite some breaks along the way.

A recent temperature anomaly forecast by NOAA’s CFSv2 longer-range model shows an impressive colder-than-normal temperature pattern right through early April across the eastern two-thirds of the nation (above; map courtesy Weather Bell Analytics, NOAA). There is reason to believe this forecast is on to something by looking at the latest GFS forecasted 500 millibar height anomalies during the next few weeks. As an example, the 500 millibar height anomaly forecast for late next week (below; map courtesy "tropicaltidbits.com", NOAA) depicts the similar upper-level pattern that has brought us cold weather during the month of February – namely a strong western North American ridge of high pressure (oranges) and a deep trough in the Northeast US (blues). This combination allows for the transport of Arctic air from northern Canada into the northern US on a consistent basis.

[06Z GFS 500 millibar height anomaly forecast for March 6th; map courtesy "tropicaltidbits.com, NOAA]

The one saving grace is that “normal” temperatures are climbing pretty rapidly as we approach the spring equinox. For example, the normal high temperature in Philly on February 23rd is 46 degrees, but by the time we reach March 23rd it climbs to 55 degrees. In other words, 10 degrees below normal a month from now won’t have quite the same sting that it has right now.

11:00 AM | *The sun has gone quiet again during the weakest solar cycle in more than a century*

latest_solar_image

[Latest solar image with little sunspot activity; courtesy "spaceweather.com"]

Discussion

Overview

The main driver of all weather and climate, the entity which occupies 99.86% of all of the mass in our solar system, the great ball of fire in the sky – has gone quiet again during what is likely to be the weakest sunspot cycle in more than a century. For the past 5 days, solar activity has been very low and one measure of solar activity – its X-ray output – has basically flatlined in recent days (plot below courtesy NOAA/Space Weather Prediction Center). Not since cycle 14 peaked in February 1906 has there been a solar cycle with fewer sunspots. We are currently more than six years into Solar Cycle 24 and today the sun is virtually spotless despite the fact that we are still in what is considered to be its solar maximum phase. Solar cycle 24 began after an unusually deep solar minimum that lasted from 2007 to 2009 which included more spotless days on the sun compared to any minimum in almost a century.

x-ray output flatlined

[The flatlining of solar X-ray output in recent days; courtesy NOAA/SWPC]

Solar maximum

The sun goes through a natural solar cycle approximately every 11 years. The cycle is marked by the increase and decrease of sunspots which are visible dark regions on the sun’s surface and cooler than surroundings. The greatest number of sunspots in any given solar cycle is designated as the “solar maximum" and the lowest number is referred to as the “solar minimum” phase. There was an uptick in the number of sunspots in April 2014 which produced a second peak during solar cycle 24 and it is looking increasingly likely that this will be considered the solar maximum point for this particular cycle (figure below courtesy NASA). Many solar cycles are double peaked; however, this is the first one in which the second peak in sunspot number was larger than the first peak which occurred in February 2012. Going back to 1755, there have been only a few solar cycles in the previous 23 that have had a lower number of sunspots during its maximum phase.

solar_cycle_24

[Sunspot numbers for solar cycles 23 and 24 (current) with second peak; courtesy NASA]

Consequences of a weak solar cycle

First, the weak solar cycle has resulted in rather benign “space weather” in recent times with generally weaker-than-normal geomagnetic storms. By all Earth-based measures of geomagnetic and geoeffective solar activity, this cycle has been extremely quiet. However, while a weak solar cycle does suggest strong solar storms will occur less often than during stronger and more active cycles, it does not rule them out entirely. In fact, the famous Carrington Event of 1859 occurred during a weak solar cycle (#10) [http://thesiweather.com/2014/09/02/300-pm-the-carrington-event-of-1859-a-solar-superstorm-that-took-places-155-years-ago/]. In addition, there is some evidence that most large events such as strong solar flares and significant geomagnetic storms tend to occur in the declining phase of the solar cycle. In other words, there is still a chance for significant solar activity in the months and years ahead.

Second, it is pretty well understood that solar activity has a direct impact on temperatures at very high altitudes in a part of the Earth’s atmosphere called the thermosphere. This is the biggest layer of the Earth’s atmosphere which lies directly above the mesosphere and below the exosphere. Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation and are highly dependent on solar activity.

Finally, if history is a guide, it is safe to say that weak solar activity for a very prolonged period of time (several decades) can have a negative impact on global temperatures in the troposphere which is the bottom-most layer of Earth’s atmosphere - and where we all live. There have been two notable historical periods with decades-long episodes of low solar activity. The first period is known as the “Maunder Minimum”, named after the solar astronomer Edward Maunder, and it lasted from around 1645 to 1715. The second one is referred to as the “Dalton Minimum”, named for the English meteorologist John Dalton, and it lasted from about 1790 to 1830. Both of these historical periods coincided with below-normal global temperatures in an era now referred to by many as the “Little Ice Age”. In addition, research studies in just the past couple of decades have found a complicated relationship between solar activity, cosmic rays, and clouds on Earth. This research suggests that in times of low solar activity where solar winds are typically weak; more cosmic rays reach the Earth’s atmosphere which, in turn, has been found to lead to an increase in certain types of clouds that can act to cool the Earth.

Outlook

The increasingly likely outcome for another historically weak solar cycle continues the recent downward trend in sunspot cycle strength that began over twenty years ago during solar cycle 22. If this trend continues for the next few cycles, then there would likely be more talk of another “grand minimum” for the sun. Some solar scientists are already predicting that the next solar cycle, #25, will be even weaker than this current one. However, it is just too early for high confidence in those predictions since some solar scientists believe that the best predictor of future solar cycle strength involves activity at the sun’s poles during a solar minimum and the next solar minimum is still likely several years away.

Paul Dorian Vencore, Inc.

8:30 AM | ****Incredible looking overall long-term pattern: afternoon/night accumulating snow with heavy squalls, damaging winds late tonight/early Sunday with possible power outages, painful cold on Sunday, multiple additional snow threats and brutal cold air outbreaks****

[Early morning NEXRAD radar image with snow over the Great Lakes/Ohio Valley and headed our way; image courtesy University of Wisconsin]

Discussion

The next 24-36 hours will bring us accumulating snow with heavy squalls, high impact winds, painful cold and dangerous sub-zero wind chills as a result of tremendous intensification of a storm system off the Northeast US coastline. This storm is currently located over southeastern Ontario and it will drop rapidly today towards the I-95 corridor region. Once this system reaches the coastal waters it will deepen explosively by some 36 millibars in a 24-hour period. The combination of the relatively warm waters of the western Atlantic Ocean, an extremely vigorous upper-level wave of energy, and a powerful upper-level jet streak will help cause this rapid intensification during the next 24 hours or so. This type of rapid and significant intensification will lead to a very sharp pressure gradient across the Northeast US which, in turn, will lead to extreme wind gusts on the order of 55 mph or so in the period between late tonight and Sunday morning (approximately 3 am to noon). Unfortunately, power outages are quite possible with this type of wind from late tonight into early which is the same time the coldest air of the season comes pouring into the region. Winds will slowly decrease later Sunday afternoon and evening.

As far as the snow is concerned, while there can be some snow seen this morning, the majority of the snow showers and possible heavier snow squalls should occur this afternoon and continue this evening. The snow part of this event will really consist of two parts: one part associated with the Arctic front from this afternoon into the late evening hours and then the second part associated with the developing storm late tonight and early Sunday. Some of the snow squalls this afternoon and evening can be quite intense with brief heavy snowfall, gusty winds, very poor visibility ("white out" conditions) and quick accumulations. Late tonight and early tomorrow will pose another chance for additional snowfall from eastern PA northeast across New Jersey and New York City as the storm deepens rapidly off the coastline. In fact, New York City could end up with its heaviest snowfall during this latter portion of the storm when an “inverted trough” extends to the northwest of the intensifying surface low pressure center. One final note on the snow, it is possible that some "thunder snow" occurs during the next 24 hour in portions of the I-95 corridor given this tremendous upper-level suport and upward motion in the atmosphere.

Accumulations by tomorrow morning are likely to be in the 1-3 inch range across Philly, a coating to 2 inches in the DC metro region, and 2-5 inches in and around NYC metro region. However, we'll have to watch for a potential surprise late tonight and early Sunday for additional snowfall in the Philly metro region and especially in the New York City metro region which could add to these preliminary accumulation estimates. Much of the snow that does accumulate will be whipped around by powerful winds late tonight and on Sunday with considerable blowing and drifting possible in some areas. Temperatures are likely to drop to single digits by early tomorrow throughout the I-95 corridor, then struggle to rise at all during the day, and then plunge to possible record-breaking territory by early Monday morning in the area of 0 degrees or even slightly below.

Another system could throw significant accumulating snow our way late Tuesday into early Wednesday, but that storm track is still somewhat uncertain. However, what is quite certain is that there will be more bitter cold air for the second half of next week and beyond and there will be multiple additional snow threats as an unbelievable long-term pattern is shaping up for the Mid-Atlantic region.