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Was prepared to post earlier…though delayed out of respect for Keith Allen/s visit
Abstract
Last winter, the rule was significant snow and sustained cold…centered in the eastern part of the country, which brought delight to many in this region who felt they were left out in 2001/02. This winter, the focus is on tremendous variance manifested in what we believe will be viscous swings back and forth in the position of the mean trough across North America.
What would this mean you ask? It would indicate that pretty much everyone across the contiguous United States should see the potential for extreme cold, unusual warmth, heavy precipitation, dry conditions and above or below normal snowfall at given times throughout the winter. Though even with this said, there should be areas which are biased warm verses cold, and snowy verses drier than average.
Forecast Methodology
The 2003/04 winter outlook takes on our “four-method” approach. Those four methods incorporate the use of climate factors (inter-seasonal oscillations, environmental/geological features and solar activity), analog years, climate models, and the point system. The points system is intended to establish the general trending of various climate factors, (i.e. determining whether those factors favor a cooler than normal, snowier than normal, drier than normal, and/or warmer than normal winter). The points system should NOT be used to make a forecast since it only makes a rough estimate of the trend. The forecast is created from a compilation of trends in climate factors, and the analog years which are based on those trends.
The points system assigns a numerical value to each factor which ranks its importance. The total points available are 101 (101 is used so that there cannot be a tie). All factors are ranked from 1 to 9; a value of one (1) would indicate the least influential factor, whereas a value of nine (9) would denote one which is very important, and essential to establishing the trend of the forecast. The categories covered in the outlook are listed below:
Inter-seasonal oscillations (climate factors)
Solar features
Environmental and Geological Factors
Special Seasonal predictors
AGCM climate model Data
Analog years
Government forecast product
Since this is a modified version of our official outlook we will forego the use of the points system, and will not be going into a great amount of depth in the assessment of the factors above…which is done in the official outlook. Also, not all factors will be discussed.
The use of the government forecast product in this outlook is to establish the trending of the many climate models which are used to create seasonal forecasts. Since the Government winter forecast is primarily based on these models (which there are too many of for me to cover herein) it makes for easy and less time-consuming analysis of those models. We began using this method last winter in order to account for the mass quantity of Numerical model output since there was too much for me to review myself (as we Previously eluted to) however its use in this particular manner was originally adopted by Joe Bastardi a Senior Meteorologist at Accuweather:
http://proa.accuweather.com/adcbin/prof ... _index.asp
The Government forecast product:
This year, NOAA has outlined equal chances for above, and below normal precipitation and temperature across the US, as we can see from the figures below:
Temperature:
Precipitation:
Complete Article:
http://www.noaanews.noaa.gov/stories2003/s2100.htm
Based on the equal chances forecasted, we can assume that the general consensus among many of seasonal climate models is for near to slightly below normal temperatures across the eastern and central portions of the country, and warmer than average conditions in the west.
The Pacific Decadal Oscillation:
The Pacific Decadal Oscillation is a multi-decadal climate factor which operates on a long term (10+ years) time scale, and is responsible for influencing the favored phase of many different short-term (high variability) oscillations in pacific basin. The PDO operates in two long-term (low to moderate variability) phases known as the cold (negative) and warm (positive) phases.
While the long term fluctuation in the Pacific Decadal Oscillation can regulate long term climactic patterns across the pacific and North America during one or the other long term phase, shorter term fluctuations in the PDO within the controlling longer-term phase can have very different effects.
During the long-term PDO cold phase, La Nina (cold phase ENSO) events are favored, however, El Nino events are common as well, though tend to be weaker, and shorter lived. During the long-term warm phase, El Nino events tend to be stronger, longer lived and far more frequent than La Nina events
The following two figures depict Sea Surface temperature anomalies in the warm and cold phase PDO in correlation with the warm and cold phases (El Nino and La Nina) ENSO events:
Pacific Decadal oscillation:
El Nino – Southern Oscillation:
As we can observe from the figures above, and as we established in the PDO description in the paragraphs above, the SSTA patterns particular to the cold phase of the pacific Decadal oscillation agree well with the SSTA configuration of a cold phase (La Nina) ENSO event. The same goes for the warm phase PDO, and warm phase ENSO (El Nino) SSTA configuration.
At the present time the pacific Decadal oscillation has been predominantly positive (warm phase), within the longer term cold cycle which started back up in 1998. This pattern is commonly associated with the formation of Weak El Nino events; centered in the central and western pacific.
Short term warm phase PDO winters within the longer term cold cycle tend to be ENSO neutral, Weak or weak to moderate El Nino winters. This winter is likely to favor similar conditions. Historically, these winters tend to be snowier and colder than average, as El Nino events in the long-term cold phase of the PDO are much different from those classic El Nino events of the PDO warm phase, therefore producing different effects. These El Nino events tend to see a weaker pacific low, (which during the long-term warm phase can become very strong) thus, allowing a decrease in the strength of the pacific jet, which during an El Nino in the long-term PDO warm phase tends to be strong, and overwhelming, forcing the storm track well to the south.
We believe that the current trend in the PDO is here to stay for at least the next six to eight months and that this winter will be a warm phase PDO Winter within the longer term cold cycle.
Furthermore, a short-term warm phase PDO within the longer-term cold cycle tends to favor the increased likelihood of more than one major east USA snowstorms.
El Nino – Southern Oscillation:
Overall trend: Neutral then weak El Nino:
The ENSO is described by the regular changes in trade wind direction, SST anomalies, and Sea Level pressure in the equatorial pacific. The El Nino – Southern Oscillation is essentially a shorter term, and higher frequency function of the longer term Pacific Decadal Oscillation.
The ENSO has three phases, Warm (positive, or El Nino) phase, and the cold (Negative, or La Nina) phase, and the Neutral phase.
In the ENSO neutral Phase, SST Anomalies in the tropical pacific are near zero, however can be biased warm (borderline El Nino) or biased cold (more reminiscent of La Nina). The links below show these occurrences:
Biased warm ENSO Neutral conditions – borderline El Nino (Using SSTA from 11/08/03):
http://www.osdpd.noaa.gov/PSB/EPS/SST/d ... 8.2003.gif
Biased cold ENSO Neutral conditions – Borderline La Nina (Using SSTA from 08/29/00):
http://www.osdpd.noaa.gov/PSB/EPS/SST/d ... 9.2000.gif
The tropical pacific is divided up into four different regions (called Nino regions) in order to better analyze the ENSO. The figure below shows these divisions:
http://www.cpc.ncep.noaa.gov/products/a ... gions.html
These regions are used to estimate SST anomalies in the classification of El Nino, and La Nina Events. NOAA classifies El Nino and La Nina events as such when SST anomalies in the Nino 3.4 region are at least 0.5 degrees Celsius above normal for three or more months. The same goes for La Nina, in which SST anomalies are at least -0.5 degrees Celsius for at least three or more months. The effects of such events however can be felt before the official classification as is the current case.
This year – as stated, we are currently dealing with categorical ENSO neutral conditions, however that said, over the past few months (since the end of August) Sea Surface temperature Have been warming steadily across the tropical pacific, which is dictated by fluctuations in the Madden-Julian Oscillation and the eastward propagation of oceanic Kelvin waves which promote warming off the SSTA across the region, in addition to the normal weakening of the equatorial easterlies and increased high level divergence perpetuated by the eastward shift in the upward portion of the walker circulation normal during El Nino events.
The figures below show SSTA evolution over the past week, month, and year:
Latest weekly product:
Latest Monthly product:
Latest Seasonal product:
Significant warming has been taking place across the far western pacific, as SSTA totals reach almost 1.5 degrees Celsius above normal between 140W and 150E centered near the dateline. Should this kind of SSTA persist thru the remainder of the month, El Nino conditions will be “officially” declared, however based on the analysis above, El Nino conditions may already be present. This type of weak El Nino centered in the central and far western pacific is typical of the El Nino events of the 1960s and 1970s.
The figures below show current Subsurface SST means and anomalies across the tropical pacific:
5-day mean:
Monthly mean:
As we can see, the depth of the 10 and 20C isotherms respectively are relatively close to the surface, at a depth of only between 50 and 300 meters, especially across the far eastern pacific both in the 5 day and monthly means. The monthly means however show the 10C isotherm depth between 300 and 400 meters. Note also how the depths of the warmest sub-surface anomalies in both comparisons are relatively shallow and cooler anomalies lurk just below the warmest anomalies. This type of set up is very common during weak El Nino events in the cold phase of the PDO, and one of the reasons why this El Nino will only be a weak to moderate event – centered in the western pacific closest to the warmest sub-surface anomalies and weakest easterly flow.’
The figures below show a comparison between SST means, anomalies and wind stress on 5-day and monthly time scales:
Oct 2003:
5-day period ending yesterday:
The greatest warming has been taking place across the western pacific, in line with the best westerly flow, and strongest sub-surface warming. It is likely that the greatest above normal SSTA associated with the developing El Nino will remain in this general location throughout the winter, though may spread east at times during MJO active phases or at times where the easterlies weaken further.
Pulsing in the Madden-Julian Oscillation may lead to increased convection across the region and promote an energizing of the sub-tropical jet stream during the winter, bolstered by the higher than normal latent heat content particular to a weak El Nino, Therefore causing increased storminess across North America.
Our thinking is that this El Nino will not be of the classic variety, and overall remain very weak; behaving like many of those in the 1960s and 1970s, associated with the long-term cold phase of the Pacific Decadal oscillation, and also be weaker than the El Nino of last winter. In order to make accurate ENSO analogs, we must analyze the trending of ENSO models. To do this, we will use the NCEP Climate model (as it displays the best long-term skill). The model forecast is shown below:
10-month SSTA anomaly:
3-season mean:
http://www.emc.ncep.noaa.gov/research/c ... cst_2D.gif
10 month subsurface anomaly:
Nino 3.0 SSTA:
http://www.emc.ncep.noaa.gov/cmb/sst_fo ... _nino3.gif
Nino 3.4 SSTA:
http://www.emc.ncep.noaa.gov/cmb/sst_fo ... nino34.gif
Time will tell if the evolution to true El Nino conditions gets underway following the close of this winter, although a weak El Nino centered in the western pacific Nino 3.4, and 4.0 regions will be present throughout the entire period, even as other indices such as those described in the paragraphs above, in addition to 850 hPa and 200 hPa zonal wind indices, Outgoing Long wave radiation (OLR) indices and the Equatorial SOI are near zero indicating ENSO neutral conditions.
After weighing the sub-surface temperature anomalies and comparing that with those of the surface trends, we feel that the current evolution to weak El Nino conditions is on track. (SSTA of between +0.5 and +1.5C on average in the equatorial pacific this winter).
The QBO:
This year will be a transitional QBO winter, in which the QBO will be shifting from east to west during the winter months. So we will begin the winter as a weak El Nino east QBO trending to a weak El Nino west QBO winter, following an El Nino west QBO to east QBO winter. Thus we may be able to expect this winter to start much like last winter ended and this winter end much like last winter began. Or basically the reverse of last winter. I realize that these comparisons are relatively complex, however especially important this year due to the transitional state of the QBO.
Research has also shown that weak QBO values (near neutral or within +/- 9.00 of zero) tend to favor severe winter conditions across the United States. Many of these winters in which such values were present were transitional QBO winters either from west to east or east to west) much like this coming winter. These winters are listed below:
Winters in which the QBO was within +/- 9.00 of neutral (0.00):
1950/51, 1951/52, 1952/53, 1953/54, 1957/58, 1961/62, 1963/64, 1977/78, 1988/89, 1993/94 1995/96, 1999/00, 2001/02, 2002/03
Winters in which the QBO shifted from east to west (between December and February):
1955/56, 1964/65, 1969/70, 1973/74, 1984/85, 1997/98, 1998/99, 1960/61, 1972/73
A good majority of these winters were severe winters across the central and eastern part of the country. Many of the years listed above can already be considered prospective analogs.
The QBO since January 2003 has been east (as previously eluted to), peaked in August and has now begun to slowly decline.
Our contention is that the QBO will be neutral to east in January Neutral to west in February, and completely west by march.
The southern oscillation Index (SOI):
A very influential factor in determining the short term fluctuations in the strength of the pacific jet stream is the Southern oscillation index or SOI. The SOI phases (negative and positive) are normally dictated by the prevailing phase of the ENSO.
Considering as how this will be a Weak El Nino winter, we are expecting the SOI to average near neutral most of the time (by that I mean +/-1.0 overall) though biased slightly toward the negative category. As El Nino conditions continue to evolve, the SOI may drop below -1.0 on the monthly average.
The North Atlantic Oscillation:
Blocking patterns associated with the negative phase of the NAO manifest themselves in three different formats:
Ireland block:
The above normal height anomaly in the means may be located as far east as Ireland and great Britain, however still qualify as a negative NAO.
Greenland Block:
Blocking develops across Greenland. This type of scenario is associated with the best potential for a major east coast snowstorm due to the likely presence of a 50/50 low.
Baffin Island / Labrador – Davis Strait / Northern Quebec blocking:
The strongest above normal height anomaly forms very far to the south and west of its normal position, between Baffin Island, northern Quebec, Labrador and the Davis Strait, which forces the mean position of the polar vortex very far to the south. This is considered an extreme position for a negative NAO and, thus one which is favorable for severe arctic intrusions, and strongly suppressed storm systems. Many southern US storm systems occur when blocking is centered in these locations.
Atlantic thermohaline Circulation:
While both negative and positive phases of the north Atlantic oscillation flip back and forth between each phase regularly, specific controlling factors can lead to one or the other phase of the North Atlantic Oscillation being favored on a seasonal, decadal and multi-decadal scale. Most notably, the two factors responsible for this are the changes in solar activity over 11 year periods and the Atlantic thermohaline circulation.
The Atlantic thermohaline circulation reflects the strength of the thermal gradient between the tropics and the Polar Regions.
A weak thermohaline circulation is defined by a stronger than average thermal gradient between the tropics and the poles. During these times the Polar Regions cool relative to normal while the tropics warm relative to normal resulting in the tightening of the gradient. The resultant forcing on the jet stream tends to promote a more zonal flow across the northern hemisphere due to the significant temperature contrasts, and therefore a tendency for a mostly positive NAO and Arctic oscillation. Also during these periods, the release of oceanic heat energy is diminished, as well as overall heat distribution, helping to suppress Atlantic hurricane activity. Seasonal Atlantic hurricane activity can be used as a means to assess the state of the Atlantic thermohaline. Decreased Atlantic hurricane activity can be very strong predictor of a weak Atlantic thermohaline in times where no strong El Nino or La Nina is present to skew Atlantic activity.
A strong thermohaline circulation reflects a weaker than average thermal gradient between the tropics and the poles. The strong phase of the Atlantic thermohaline circulation is essentially the reverse of the weak phase. During these periods the thermal gradient between the tropics and the poles weaken, promoting a tendency for a weaker jet across the northern hemisphere, increased hurricane activity through the increased release of oceanic heat, and the more even distribution of heat between the tropics and the high latitudes. This sequence of events is most commonly associated with the tendency for high latitude blocking, a predominantly negative AO, and NAO; Higher than average Atlantic hurricane activity during the hurricane season can be regarded as a good indicator of a strong Atlantic thermohaline.
The Atlantic tripole (water temperature configuration) responds and conforms to the phase of the thermohaline circulation. Typically in periods when the thermohaline circulation is weak (strong horizontal thermal gradient) the Atlantic tripole configuration features cold water in the north Atlantic, warm central and cold tropical making up the tripole. This water temperature configuration favors the strong intensification of the Azores high and Icelandic low due to the water temperature gradient in the Atlantic between the cold north and warm central. Water temperatures during the weak cycle of the Atlantic thermohaline circulation tend to be cooler on average globally. In the strong cycle of the Atlantic thermohaline, the thermal gradient weakens between the poles and the tropics, allowing a more even distribution of heat and energy. Since the distribution of heat and energy are more even, the jet stream weakens and the pattern becomes more progressive. As a result, the Atlantic tripole reverses and warm water is found in the north Atlantic, and the equatorial Atlantic, with the remaining cold water in-between. This water temperature configuration allows for the weakening of the Icelandic low and Azores high, forcing the favored phase of the North Atlantic oscillation and Arctic Oscillation to negative. During this period, water temperatures tend to be warmer than normal globally and Atlantic hurricane activity, above normal. The bond between the Atlantic thermohaline circulation, the tripole and the North Atlantic oscillation is such that the phase of the Atlantic thermohaline circulation will almost completely dictate the favored phase of the North Atlantic oscillation, except in the case when the thermohaline circulation is strong and sunspot numbers are elevated (mainly above 1700), in which cases the North Atlantic Oscillation tends to be primarily positive, most notably the winter of 2001/02, when high solar activity forced the North Atlantic Oscillation to remain mostly positive throughout nearly the entire winter. Situations such as these however are highly uncommon and will most likely only occur once every 11 to 22 years consistent with a strong thermohaline circulation and the 11 year sunspot maximum.
High solar activity has been shown to increase the strength of the Icelandic low, thus promoting a positive NAO regardless of forcing from the Atlantic thermohaline.
The Atlantic thermohaline circulation phases normally last 20 to 30 years, however just as with the PDO, short term fluctuations in the Atlantic thermohaline phase can occur as well. These short term changes can last just a few months or as long as a few years. The most notable of these mid-phase reversals occurred during the early and mid 1970s. These regular change sin the ATC have been occurring since the last ice age. Over the past 100 years, the ATC has gone through two complete weak cycles and one complete strong cycle.
The Arctic Oscillation:
The Arctic oscillation is a larger-scale subsidiary feature of the North Atlantic Oscillation which is characterized by the regular flip-flop in pressure across the arctic regions (most specifically the North Pole and Iceland) that is also controlled by the rhythms of the Atlantic. The Arctic oscillation, similar to the North Atlantic Oscillation, goes back and forth between both phases regularly. Those two phases are the positive (warm) and negative (cold) phase. Each phase lasting about two weeks before once again reversing back to the previous phase
The short term, seasonal and decadal scale fluctuations in the Arctic oscillation are forced by the following factors:
The Atlantic Thermohaline circulation:
A strong ATC would help weaken the northern hemispheric thermal gradient, increase he distribution of heat between the Polar Regions and the tropics, therefore promoting a weaker polar vortex and more potential for blocking. This predictor is used mainly to determine the favored phase of the Arctic oscillation on a seasonal, decadal, and multi-decadal scale. A weak ATC would argue for the tightening of the northern hemispheric thermal gradient due to the warming of the tropics and the cooling of the Polar Regions relative to normal and one another. The steep thermal gradient between the two regions results in the contracting and strengthening of the vortex, leading to a primarily Positive AO.
Solar Activity (10.7cm radio flux):
High 10.7 radio solar flux tends to promote the weakening of the Aleutian low, strengthening of the Icelandic low, and a more zonal flow globally. This would lead us to a predominantly positive arctic oscillation. At times when flux is low, other oceanic and atmospheric here on earth control the seasonal tendencies of the arctic oscillation.
Stratospheric temperature:
This idea assumes the fact that releases of stratospheric heat will eventually work its way downward through the atmosphere leading to thermal ridging and the development of blocking high pressure in the high latitudes.
Northern Hemispheric Snow cover:
When northern hemispheric Snow cover is above normal, the strength of the Siberian high is amplified, thus relating to the weakening of the polar vortex and a mostly negative Arctic oscillation. Low Northern hemispheric snow cover my also indicate a predominantly positive Arctic oscillation.
With a strong ATC, High Northern hemispheric Snow cover, and decreasing solar activity, it is highly likely that the Arctic oscillation will average negative this winter.
Eastern pacific Oscillation:
The Eastern Pacific Oscillation is the name given to the regular flip-flop in pressure across the far eastern pacific and Gulf of Alaska. Similar to the North Atlantic Oscillation and Arctic oscillation, the Eastern Pacific Oscillation also has two phases, those being, Positive (the warm phase) and Negative (cold phase). Since the Eastern Pacific Oscillation exhibits a great deal more inter-seasonal variability than that of the North Atlantic oscillation or ENSO, it makes it much harder to accurately predict on a seasonal scale.
SSTA in correlation w/ the EPO Positive Phase:
SSTA in correlation w/ the EPO negative Phase:
Research has shown that the favored seasonal phase of the Eastern Pacific Oscillation is forced by the following factors:
Solar Activity:
Very high 10.7cm radio flux and geomagnetic influences can lead to a weakening of the Aleutian low, thus promoting a positive Eastern pacific Oscillation. High pressure relative to normal is located in the position where the Aleutian low should have been, pushing the mean through to the east. Cold water off the west coast during the winter season is a signal for troughing. Warmer water is a ridge building signal. Since high solar activity weakens the Aleutian low, the positive phase of the EPO is more common.
Sea Surface Temperature Anomaly (SSTA) configuration:
When looking for a positive EPO, one would like to see warm water to the north of Hawaii, bounded by cold water to the north and east of the warm pool, encompassing the Gulf of Alaska. For a negative EPO, one would like to see warm water in the Gulf of Alaska, with cold water to the north of Hawaii.
Observed phase of the ENSO:
Normally, El Nino events favor the formation of warm pools in the Gulf of Alaska, leading to the negative Phase of the EPO being favored over the positive phase. La Nina events favor the opposite, in which warm water normally develops to the north of Hawaii, and cold water develops in the Gulf of Alaska, which is consistent with the necessary SSTA set-up for a Positive EPO.
4) The Pacific Decadal Oscillation:
the cold phase of the pacific Decadal Oscillation, which is consistent with La Nina conditions characterizes the development of a warm pool from the northeast coast of the Asian continent westward to just northeast of Hawaii, while colder water is forced westward against the north American coast. In the warm phase of the PDO, cold water replaces this warm pool from just northeast of Hawaii westward to the west coast Asia. This is consistent with El Nino conditions, and the formation of a Negative EPO.
This year, we expect that the EPO will average neutral to negative, consistent with the current SSTA configuration, transition to El Nino, and the PDO warm phase.
Effects of the Solar Cycle on global patterns:
The term 10.7cm radio flux describes the measure of solar radio emissions at a wavelength of 10.7 centimeters which are released from hot gasses trapped within the magnetic loops.
Both enhanced 10.7cm flux and high geomagnetic activity which occurs during the solar maximum has significant to severe impacts on our normalized weather patterns here on earth during all seasons, however most notably, these effects are felt the most in the late fall, winter, and early spring.
The following features are most significantly affected by high geomagnetic activity:
Changes in the strength of the Aleutian and Icelandic low pressure centers:
Significant geomagnetic activity can cause the weakening of the Aleutian low, while allow for the strengthening of the Icelandic low, resulting in a dominating RNA (trough in the west ridge in the east) or fast west to east (zonal) flow across the northern hemisphere. Recall the weakening of the Aleutian low and strengthening of the Icelandic low results in appositive EPO and Positive NAO which leads to a predominantly negative PNA (RNA) pattern during winter.
Less Cloud cover (Svensmark Effect):
During periods when solar activity is very high, the earth’s natural protective magnetic field is the strongest, which tends to block cosmic ray neutrons from entering the atmosphere. Long-term observations have shown that during periods of high geomagnetic activity, these neutrons are significantly less than what they would normally be near to solar minimum. These neutrons have an ionizing effect that aids in the production of clouds (an effect which is increased greatly, especially when there are higher levels of volcanic ash and aerosols present in the atmosphere). The reduction of cloud neutrons during the solar maximum has been shown to have a diminishing effect on the amount of cloudiness globally, leading to less precipitation, drought, and possibly warmer surface temperatures due to the decreased soil moisture, and increased surface heating due to the direct effect of the decrease in cloudiness its self. This relationship is shown in the figure below:
Large-Scale Effects on the Low and Mid-latitudes:
High solar flux activity (increased 10.7cm radio flux, luminosity, solar irradiance and UV), produce a chemically based reaction on ozone which leads to increased temperatures in the mid and lower latitudes. This warming eventually feeds-back to thermal ridging and above normal heights, even in spite of factors here on earth arguing for different effects. It is at these latitudes where the effect of the forcing from the increased flux is the strongest.
The High geomagnetic activity cycle is often offset from the sunspot and flux cycle, thus the effects of increased solar activity overall, can have the greatest effects in different locations. High sunspot numbers and flux tend to have the greatest effects in the lower and mid-latitudes, while the high geomagnetic activity cycle has the greatest effects on the Polar Regions. High geomagnetic, and flux activity occurring at the same time can result in the warmest possible weather patterns here on earth during the winter season. This is because larger coronial mass ejections or CME’s associated with increased geomagnetic activity, (produced by dying flares/sunspots and Coronial holes) are favored a this stage of the solar cycle.
Large-Scale Effects on the High latitudes:
High geomagnetic activity effects the high-latitudes the greatest due to the fact that the geomagnetic waves and charged particles are drawn to the earth’s magnetic poles, thus the effects are felt the strongest in the polar regions. This activity, as previously eluted to can lead to the strengthening of the Icelandic low and weakening of the Aleutian low.
Since the sun goes through a 27 day rotational cycle, we can see that the large sunspots associated with regions 486 and 488 are now beginning to rotate back toward the visible disk (which is the region of the sun which is visible to earth). In the short-term however, as we can tell from the figure on the right, there have not been any significant flares or geomagnetic storms. This recent lack of activity has lead to the strong decrease in radio flux over the past two weeks.
Radio flux values should continue to increase as the sunspots re-emerge, and then begin to drop once the activity subsides toward the first of December.
http://www.dxlc.com/solar/
The activity maximum (in which flux values and sunspot numbers were the highest) occurred in late October, once the sunspots responsible for producing the high activity (as we discussed) moved off of the visible disk, solar flux and sunspot numbers plunged. Following the peak, radio flux values plunged into the 990s, and are just now beginning to rebound.
Give our current position in solar cycle 23, it is my contention that once the sunspots re-appear on the visible dick this coming week, it is not likely that they will not be as strong, nor produce the same extreme effects. However, with this said, there will be another increase in flux and geomagnetic activity in the coming days.
The following figures show the forecasted sunspot and solar flux values for the remainder of solar cycle 23:
http://www.sec.noaa.gov/SolarCycle/
As the figures above would indicate, both the 10.7 CM flux progression and sunspot values would support the continued downslide in solar activity as we trend toward the solar minimum.
Environmental and Geological features:
This section of the article covers specific environmental and geological factors which have an impact on our weather patterns.
Arctic and northern hemispheric snow cover:
Arctic and northern hemispheric snow cover is very important when considering the tendency for significant arctic outbreaks into the mid-latitudes during the late fall, winter and early spring, as well as in deciding the favored seasonal phase of the arctic oscillation.
Northern Hemispheric Snow cover and the Arctic oscillation:
Years with significant Northern hemispheric snow cover tend to favor the strengthening of the Siberian high in the means and therefore has the potential to influence the Arctic oscillation into the negative phase, as the enhanced Siberian high force increases in heights across the polar regions, which is necessary for a predominantly negative Arctic oscillation on a seasonal scale. Years with decreased snow cover, normally see a weaker Siberian high in the means which leads to a decrease in the strength of the Siberian high and a tendency for a Positive AO. Other factors may however have a stronger influence on the AO resulting in the opposite phase prevailing on a seasonal scale in spite of the forcing from the snow cover.
Influence on the Caspian Connection:
When northern hemispheric snow cover is greater than average on the Siberia side of the pole in relation to what it may be on the north America side, the formation of colder air masses overtop of the more significant snow cover on the Asia side can be increased, thus when they are shunted over the pole onto the north America side, courtesy of ridging east of the Caspian (the Caspian Connection) they tend to have two effects, the first is to increase snow cover on our side of the pole, and the second is to promote the strengthening of arctic air masses, which given the correct pattern, and invade north America with severe cold.
Less snow cover on the Siberian side of the pole normally leads to the suppressed production of cold air masses in that location, thus once the Caspian connection is present, the cold air which is pushed over the pole onto the North America side is diminished in strength. During these periods, the cold air source becomes the north America side, which if less than average snow cover is present in this location as well, given the right pattern, the strength of the cold air masses invading north America are not as cold as what they could potentially be given stronger snow cover.
Northern hemispheric Snow cover and severe cold air masses:
Heavier snow cover tends to promote the formation of higher pressures overtop of it, leading to the production of cold air masses, it also helps to reflect the suns rays back out into space during the day preventing surface warming and increasing radiational cooling at night. All of these factors together lead to the formation of severe cold air masses across the polar regions in the late fall and winter. If decreased snow cover is present, the exact opposite of what is described above usually is the standard.
This year, northern hemispheric snow cover was off to a very slow start; however, by the end of October, had undergone explosive expansion, reaching the third most expansive levels since records began in the 1960s. October 2003 snow cover was the third most expansive on record behind only 1972, and 1976. The figures below show the slow start and the explosive finish at the conclusion of October:
October 1, 2003:
November 1, 2003:
While significant increases in snow cover between October 1, and November 1, are very common, below average snow cover going into October is frequently a precursor to below average snow cover the rest of the month and the following winter.
This year was the exact opposite. The slow start was quickly halted, as the snow cover, especially on the Asia side all but exploded in the following three weeks. This is a trend which has persisted even up through this point.
Given the fact that going into the first week of November, Northern Hemispheric snow cover was the third greatest on record, behind 1972 and 1976, it is easy for one to surmise that the effect of the snow cover will likely perpetuate the tendency for a negative Arctic oscillation, and increases in the potential for severe cold outbreaks, from those air masses originating on the Asia and North America Side of the pole.
Atmospheric Volcanic ash and aerosol loading:
As many are aware, major volcanic eruptions can spew large amounts of ash high into the atmosphere. These geological events can impair the amount of sunlight and produce an enhancing effect on the production of cloud neutrons which can lead to the increased production of clouds and better precipitation efficiency. High levels of atmospheric aerosols have been shown to trap incoming solar radiation and thus helping to reduce global temperatures and the effectives of 10.7 cm solar flux in winters near the sunspot maximum.
During the past hundred years, there have been several major volcanic eruptions, which have affected lower-troposphere temperatures. These sunlight impairments are not significant enough to cause a major drop in temperature, where summertime temperatures fail to exceed 70 degrees Fahrenheit on average, however, can cause global temperatures to average up to 2 degrees colder for at least two years following a major volcanic eruption(s), although most eruptions will only cause temperature drops between 0.5 and 0.8 degrees. Two significant eruptions within a year of one another can increase the effect on temperatures two fold.
Since 1979, there have been three notable volcanic eruptions which would be considered major. They were El Chichon in the mid 1980s and Mt. St. Helens, Mt Pinatubo, and Cerro Hudson in the early 1990s.
At the present time, there have been no significant volcanic eruptions on a scale which would be capable of producing such global cooling effects. During the 1970s and 80s, much research was done regarding the connection between the destruction of the ozone layer and atmospheric aerosol levels. One basic component of aerosols which causes this damage is bromine. Once legislation was passed regulating aerosol emissions to protect the ozone layer, the atmosphere has become very clean. By this, the total amount of stratospheric aerosol has dropped rapidly since the late 1980s. The low aerosol level combined with the fact that the effects from the last series from major volcanic eruptions have diminished, it can be determined the atmosphere will not inhibit the passage of sunlight through the atmosphere, to the surface, which would suggest that these two factors will do little to inhibit solar based surface heating.
Furthermore, the high geomagnetic activity of recent has the potential to disrupt the earth’s tectonic plates resulting in volcanic eruptions, which given one severe enough, could affect the amount of sunlight which is able to make it to the earths surface, resulting in cooler temperatures globally.
Though the low volcanic ash and aerosols are essentially a non-signal, it would not inhibit sunlight from reaching the surface, perhaps resulting in warmer temperatures
2003 Atlantic and Pacific Hurricane activity:
The hurricane activity and landfall factor allows us to analyze the interaction between the tropics and northern hemisphere by considering the following things:
1) Total number of named storms in the Atlantic as compared to the pacific
3) The relation between tropical systems, Atlantic SST configuration, and the NAO
4) Number of United States landfalls.
This season has had a well above average number of named storms (14), as compared to the average of 9.6. The total number of storms was 19, making 2003 one of the most active hurricane seasons on record. The Atlantic season was obviously more active than the pacific season, though only by a marginal amount. Although Atlantic activity was much more prevalent in 2003 than pacific activity, the pacific did have a greater number of named storms than what the Atlantic did.
The most important factor here is that the Atlantic had three major hurricanes in 2003, (category 3 to 4), and one intense hurricane (Isabel) which was a category 5. The pacific had no category three or greater hurricanes in 2003.
In total, the 2003 hurricane season has seen 6 United States landfalls, which is above normal. The higher than average Atlantic activity, as compared to the lesser pacific activity leads us to believe that in spite of any moderate to strong El Nino or La Nina, the Atlantic signal will be the dominant controlling factor over north American weather patterns this winter.
West Pacific Warm Pool:
This is a factor which is not always present every year, however can be very important in winters where it is, as it can translate to a very cold January, providing that other factors favor its prevalence. Since it is overall a secondary factor, other primary factors can either act to enhance its effects, or suppress them.
This factor was present during the warm winter of 2001/02, however, because of other factors arguing strongly against its prevalence. Its effects were felt slightly. Had this factor not been present, it is my opinion that the winter of 2001/02 would have been nearly snow less here in the northeast. This however is a discussion for another article.
The idea (Palmer and Owen et al 1986) assumes that the warm pool will lead to the formation of a 200 hPa ridge over Japan which would translate to a strengthening of the Aleutian low, and a primarily positive PNA pattern, with a ridge in the western part of the country and a trough in the east.
The reason why the SSTA warm pool in the pacific was ineffective in 2001 was due to the EPO extreme positive phase and solar flux which lead to the weakening of the Aleutian low in the means.
There are two primary storm tracks, one which we have seen quite frequently this fall (from southern California to the lakes) and the other which I fell will be very prevalent this winter, from the Gulf of Mexico, up the east coast. The storm tracks eluted to previously will likely be the two dominant storm tracks this winter.
This year, given the fact that the same factors which drowned the feature out in 2001/02 are reversed, they will likely aid in its ability to influence the pattern this year.
AGCM climate model Data:
In seasonal forecasting, the AGCM climate model over the past 10 years has shown a considerable amount of skill in long-range forecasting. This has been especially evident in winter, where the AGCM has proved superior to other models.
As many are aware, climate models create seasonal forecasts of various different parameters i.e.…500Mb heights, precipitation, temperature, and so on. These parameters are calculated from current observations around the world at the time which the model is initialized. The input data is then converted into an exponential equation upon which is the basis for the forecasting the various parameters specific to the model. The AGCM on the other hand uses a system to calculate various atmospheric and surface parameters based on the forecasted phase of the El Nino Southern Oscillation. It then calculates the various atmospheric features which would be consistent with whichever phase of the ENSO it is forecasting. The AGCM specifically calculates 6 different parameters, four of which will be assessed herein. These parameters are listed below.
1. ENSO Forecast
2. Global 200mb Heights / Global 200mb Eddy heights
3. US temperature
4. US precipitation
This run of the AGCM which we are about to take a look at was initialized on November 10, 2003.
ENSO Forecast:
The AGCM continues to develop Weak El Nino conditions, centered in the Nino 3.4, 4.0 and the crucial area west of the international dateline, which can translate to an extremely cold January. converse to what the normal ENSO models are favoring, the AGCM once again brings SSTA in the Pacific back to near Neutral during the March to May 2003 period. The fact that the AGCM ENSO forecast seems to be in line with what the NCEP ENSO model is favoring for the coming winter I feel that the AGCM should have a decent handle on the pattern.
Remember, the AGCM atmospheric, temperature and precipitation forecasts are based on the tropical pacific SSTA forecast, thus, if the model has a good handle on SSTA in the pacific, it should have a decent handle on atmospheric patterns as well.
Global 200mb Heights and 200mb eddy heights:
http://www.emc.ncep.noaa.gov/cmb/atm_fo ... urrent.gif
There are many critical things here. First of all is the fact that the AGCM supports the ideas we outlined for a negative NAO this winter. Note the strong blocking heights over Greenland, and the 50/50 low off the coast of Newfoundland. Notice the strong positive 200 hPa anomaly centered near Japan in the first two periods. This would strongly support the ideas we outlined on the influence of the western pacific warm pool. The strong above normal height anomaly in that position argues for a below normal height anomaly near the Aleutian islands, which is necessary to pump the ridge in the western part of the country, strengthen the vortex near Hudson’s bay and promote a positive PNA pattern.
Furthermore, we note the tendency for ridging in central Asia, which could also be the precursor to a tendency for ridging east of the Caspian, and the frequent intrusion of cross-polar air masses.
US temperature:
The following figure shows AGCM forecasted surface temperature Anomalies:
The AGCM 2 meter temperature anomaly forecast is very much in line with the AGCM 200mb height forecasts and the ideas we have been establishing throughout the article. Note the tendency for below normal temperatures across the central and eastern parts of the country, while temperatures are forecasted well above normal across the high latitudes, significant of high latitude blocking.
US precipitation:
The following figure shows AGCM forecasted precipitation anomalies:
The trending in the AGCM precipitation forecast is also very much in line with what is normal for El Nino conditions west of 150 degrees west longitude in the western pacific. Thus this factor would strongly argue for above normal snowfall in the places which we outlined in the section on the western pacific warm pool.
We will not be issuing a final forecast, that part will be left up to you. We will take your questions on temperature precipitation or snowfall tonight from 9 PM on...reply to the thread or send us a PM with you question and one of us will do our best to answer it for you. All Questions WILL be answered on a first come first serve basis.
Hope everyone enjoyed it.
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RNS/Erica L.
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Any comments on this would definitely be appreciated!
Thanks again RNS and Erica, and keep up the good work!!
