March 17 Weekly Report
Written by Sig Silber
The chances of an El Nino for next winter are increasing or at least more forecasting agencies are signing on and the short term forecast suggests Spring is here.
Lets talk first about El Nino.
The Australian Government Bureau of Meteorology has their own model and this is their recent forecast:
Then there is the U.S. report. Note that 1.0 on the scale indicates El Nino type conditions. However those conditions have to exist for an extended period of time before an El Nino is declared. It is very similar to the criteria for declaring a recession but a bit longer.
What does ENSO mean for us next winter. According to NOAA:
“During warm (ENSO) episodes the normal patterns of tropical precipitation and atmospheric circulation become disrupted. The abnormally warm waters in the equatorial central and eastern Pacific give rise to enhanced cloudiness and rainfall in that region, especially during the boreal winter and spring seasons. At the same time, rainfall is reduced over Indonesia, Malaysia and northern Australia. Thus, the normal Walker Circulation during winter and spring, which features rising air, cloudiness and rainfall over the region of Indonesia and the western Pacific, and sinking air over the equatorial eastern Pacific, becomes weaker than normal, and for strong warm episodes it may actually reverse.
The increased heating of the tropical atmosphere over the central and eastern Pacific during warm episodes, affects atmospheric circulation features, such as the jet streams in the subtropics and in the temperate latitudes of the winter hemisphere. The jet streams over the eastern Pacific Ocean are stronger than normal during warm episodes (see seasonal atmospheric circulation features). Also, during warm episodes extratropical storms and frontal systems follow paths that are significantly different from normal, resulting in persistent temperature and precipitation anomalies in many regions.
By studying past warm episodes scientists have discovered precipitation and temperature anomaly patterns that are highly consistent from one episode to another. Significant departures from normal are shown in the accompanying figures for the Northern Hemisphere winter and summer seasons. Within the tropics, the eastward shift of thunderstorm activity from Indonesia into the central Pacific during warm episodes results in abnormally dry conditions over northern Australia, Indonesia and the Philippines in both seasons. Drier than normal conditions are also observed over southeastern Africa and northern Brazil, during the northern winter season. During the northern summer season, Indian monsoon rainfall tends to be less than normal, especially in northwest India where crops are adversely affected. Wetter than normal conditions during warm episodes are observed along the west coast of tropical South America, and at subtropical latitudes of North America (Gulf Coast) and South America (southern Brazil to central Argentina).
During a warm episode winter, mid-latitude low pressure systems tend to be more vigorous than normal in the region of the eastern North Pacific. These systems pump abnormally warm air into western Canada, Alaska and the extreme northern portion of the contiguous United States. Storms also tend to be more vigorous in the Gulf of Mexico and along the southeast coast of the United States resulting in wetter than normal conditions in that region.”
This is likely to impact commodity prices in those areas which will be wetter or drier than usual. More on that in the coming weeks.
Now for the Short-term (6 – 14 Day Forecast)
Notice that this is a forecast for March 23 through the end of March not today through day five.
The NOAA explanation for this forecast which they rate as 5 out of 5 relative to their level of confidence is below. Note the East Coast remains cold but the geographical extent of the colder than climatology conditions recedes in what they call the second week of the forecast and almost the entire region becomes increasingly wet over the course of the forecast period except for New Mexico where I live. Looks like we will have to wait for next winter for El Nino snows and hope that this summer brings a productive Southwest Monsoon.
“6-10 DAY OUTLOOK FOR MAR 23 – 27 2014: TODAY’S ENSEMBLE MEAN FORECASTS ARE IN VERY GOOD AGREEMENT ON THE EXPECTED 500-HPA HEIGHT PATTERN FOR THE 6-10 DAY PERIOD OVER NORTH AMERICA. A DEEP TROUGH IS EXPECTED TO PERSIST OVER MUCH OF THE EASTERN TWO THIRDS OF THE CONUS, A TROUGH IS FORECAST IN THE GULF OF ALASKA, AND RIDGES ARE EXPECTED OVER THE NORTHWEST CONUS AND OVER MUCH OF ALASKA. THE ONLY REGION WITH SOME SLIGHT DISAGREEMENT AMONG THE MODELS IS OVER THE WESTERN CONUS WHERE THE LATEST GFS DETERMINISTIC AND ENSEMBLE MODELS FORECAST WEAKER RIDGING THAN THE OTHER MODELS. THIS UNCERTAINTY IS ALSO SHOWN IN TODAY’S ENSEMBLE SPAGHETTI DIAGRAMS, WHICH INDICATE RELATIVELY HIGH UNCERTAINTY IN THE STRENGTH OF THE RIDGING IN THE WESTERN CONUS AND ESPECIALLY INTO ALASKA. TELECONNECTIONS OFF OF THE NEGATIVE HEIGHT ANOMALIES THAT ARE FORECAST IN THE EASTERN CONUS AND IN THE GULF OF ALASKA INDICATE RIDGING OVER THE WESTERN CONUS THAT IS MORE CONSISTENT WITH TODAY’S ECMWF DETERMINISTIC AND ENSEMBLE MODELS, SO THEY WERE FAVORED IN TODAY’S MANUAL 500-HPA HEIGHT BLEND. WELL BELOW-NORMAL HEIGHTS FORECAST OVER THE EASTERN CONUS, COMBINED WITH ANOMALOUS NORTHERLY FLOW OF COLD CANADIAN AIR, LEADS TO HIGH PROBABILITIES OF BELOW-NORMAL TEMPERATURES IN THE EASTERN TWO THIRDS OF THE CONUS, ESPECIALLY OVER THE GREAT LAKES REGION AND THE NORTHEAST. ANOMALOUS RIDGING OVER THE WESTERN CONUS INCREASES THE CHANCES FOR ABOVE-NORMAL TEMPERATURES THERE. ANOMALOUSLY COLD CONTINENTAL FLOW FROM CANADA INTO THE ALASKAN PANHANDLE AND SOUTHEAST ALASKA ENHANCES THE LIKELIHOOD FOR BELOW-NORMAL TEMPERATURES THERE. WELL ABOVE-NORMAL HEIGHTS FAVORS INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES ELSEWHERE IN ALASKA. A STALLED FRONTAL BOUNDARY FORECAST ALONG THE GULF COAST SUPPORTS AN ACTIVE SOUTHERN STORM TRACK, INCREASING THE PROBABILITY FOR ABOVE-MEDIAN PRECIPITATION FROM SOUTHERN TEXAS, THROUGH THE GULF COAST STATES, AND INTO THE SOUTHEAST. THE NORTHERN STREAM IS ALSO FORECAST TO BE ACTIVE, WITH SEVERAL SHORT-WAVES FORMING AND TRACKING OVER THE NORTHERN CONUS, LEADING TO AN ENHANCED LIKELIHOOD OF ABOVE-MEDIAN PRECIPITATION OVER MUCH OF THE NORTHERN CONUS. ANOMALOUS RIDGING IN THE WESTERN CONUS FAVORS HIGHER PROBABILITIES OF BELOW-MEDIAN PRECIPITATION OVER SOUTHERN CALIFORNIA AND PARTS OF THE FOUR CORNERS REGION. A STORM SYSTEM FORECAST TO MOVE ONSHORE IN THE WESTERN U.S. LATER IN THE FORECAST PERIOD FAVORS AN INCREASED CHANCE FOR ABOVE-MEDIAN PRECIPITATION IN NORTHERN CALIFORNIA, PARTS OF THE GREAT BASIN, AND THE NORTHWEST. ANOMALOUSLY DRY CONTINENTAL FLOW OVER MUCH OF ALASKA ENHANCES THE LIKELIHOOD OF BELOW-MEDIAN PRECIPITATION FOR MOST OF ALASKA, EXCEPT FOR SOUTHWESTERN ALASKA AND PARTS OF THE ALEUTIANS, IN WHICH A POSSIBLE STORM SYSTEM WILL INCREASE THE CHANCES FOR ABOVE-MEDIAN PRECIPITATION.
8-14 DAY OUTLOOK FOR MAR 25 – 31 2014: THE FORECAST 500-HPA HEIGHT PATTERN IN THE WEEK-2 PERIOD IS VERY SIMILAR TO THAT FOR DAYS 6-10, EXCEPT THE 500-HPA PATTERN IS A BIT LESS AMPLIFIED. THE PROBABILITY FORECASTS FOR TEMPERATURE ARE ALSO SIMILAR, EXCEPT THAT THERE IS LESS RIDGING EXPECTED OVER THE NORTHWESTERN CONUS, LEADING TO ENHANCED PROBABILITIES OF NEAR-NORMAL TEMPERATURES INSTEAD OF ABOVE-NORMAL TEMPERATURES. THE PRECIPITATION PATTERN IS ALSO VERY SIMILAR, WITH A FEW DIFFERENCES NOTED. AN EXPECTED INCREASE IN STORM SYSTEM ACTIVITY OVER MUCH OF THE CONUS LEADS TO THE AREAS OF ABOVE-MEDIAN PRECIPITATION IN THE 6-10 DAY PERIOD BECOMING MORE WIDESPREAD DURING THE WEEK-2 PERIOD. AN EXPECTED LACK OF STORM-SYSTEM ACTIVITY OVER ALASKA IN THE WEEK-2 PERIOD FAVORS ENHANCED PROBABILITIES OF NEAR TO BELOW-MEDIAN PRECIPITATION OVER MUCH OF ALASKA.”
