31 March 2015 Weather and Climate Outlook – Special Edition on NOAA April Update

Written by Sig Silber

NOAA has issued their April updated Outlook for both Temperature and Precipitation and it is significantly (but not totally) different from the Outlook issued on March 19.  But the U.S. Southwest will not be as wet or cool as previously thought and the Southeast will be a lot warmer and wetter than previously thought. There are other changes mostly in the nature of expanding or contracting the area that will be different than climatology. In my mind, the validity of the two subsequent months in the Three – Month Outlook are called into question by this fairly substantial revision to the April Outlook which really is a pattern change not just an adjustment.

This is a Special Edition of my weekly Weather and Climate Update Report. It covers only the NOAA April Update Issued today.

Let us take a look at what was issued today March 31, 2015 for April as compared to what was issued on March 19, twelve days ago.

The above is the preliminary release which NOAA calls their Early Outlook and below is both the updated April and the prior Three-Month Outlook. The Three-Month Outlook is not scheduled to be updated until April 16.

The Temperature Outlook for April now is very different and for the Southwest the above climatology precipitation, which I always considered strange, has been erased.

You will also notice that the Early Update for April was similar to the Three-Month Outlook so one wonders if the Three-month Outlook will be changed on April 16. We will have to wait to see. I notice the Three-Month Outlook is labeled as having been issued yesterday but I do not think that is correct.

And here are excepts from the discussion that was issued with the Outlook Map Update.

“30-DAY OUTLOOK DISCUSSION FOR APRIL 2015

THE APRIL UPDATED OUTLOOK SHOWS SOME SUBSTANTIAL CHANGES FROM THE HALF MONTH LEAD OUTLOOK. A POTENTIAL CIRCULATION CHANGE FROM RECENT WEEKS IS INDICATED BY MUCH OF THE NUMERICAL GUIDANCE AND ADDS CONSIDERABLE UNCERTAINTY TO THE APRIL OUTLOOK. THIS IS TRUE FOR BOTH TEMPERATURE AND PRECIPITATION.

BEYOND APPROXIMATELY THE FIRST WEEK OF APRIL, EXTENDED RANGE MODEL GUIDANCE NOW INDICATES CONSIDERABLY MORE TROUGHING ACROSS THE WESTERN CONUS AND RIDGING OVER THE SOUTHEAST U.S. AN ANTICIPATED COLD START TO THE MONTH ACROSS THE NORTHEAST U.S. STILL SUPPORTS ELEVATED PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHEAST AND EASTERN GREAT LAKES, PRIMARILY NEW ENGLAND. THIS AREA IS SCALED BACK FROM THE PREVIOUS VERSION OF THE OUTLOOK. MEAN SOUTHWESTERLY FLOW AND FORECAST RIDGING OVER THE SOUTH-CENTRAL U.S. AND SOUTHEAST SUPPORTS AN EXPANSIVE AREA OF FAVORED ABOVE NORMAL TEMPERATURES FOR A REGION FROM THE CENTRAL AND SOUTHERN PLAINS TO THE ATLANTIC COAST.

NOW FORECAST TROUGHING ACROSS THE FAR WEST RESULTS IN THE REMOVAL OF MUCH OF THE AREA WHERE ABOVE NORMAL TEMPERATURES ARE FAVORED IN THE PREVIOUS VERSION OF THE APRIL TEMPERATURE OUTLOOK. MONTH LONG INTEGRATIONS OF THE CFS, WHICH HAD BEEN FORECASTING HIGH PROBABILITIES FOR ABOVE NORMAL TEMPERATURES DURING APRIL, ARE NOW FORECASTING NO CLEAR TILT TO ANY ONE CATEGORY OVER MOST OF THE WEST. THEREFORE, EQUAL CHANCES IS NOW HIGHLIGHTED FOR MUCH OF THE WEST EXCEPT FOR AREAS VERY CLOSE TO COAST WHERE SSTS REMAIN ABOVE AVERAGE. COVERAGE AND PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ACROSS INTERIOR AND NORTHERN ALASKA HAVE BEEN REDUCED FROM THE HALF MONTH LEAD OUTLOOK AS A STRONG TROUGH IS FORECAST TO IMPACT THIS REGION IN THE EXTENDED RANGE.

THE AREA OF ENHANCED ODDS OF ABOVE MEDIAN PRECIPITATION FOR THE SOUTHEAST CONUS HAS BEEN EXPANDED SUBSTANTIALLY TO THE NORTH TO INCLUDE THE TENNESSEE VALLEY, OHIO VALLEY AND MID-ATLANTIC IN RESPONSE TO STRONG SOUTHWESTERLY MEAN FLOW AND THE LIKELY ACTIVE STORM TRACK GIVEN THE ANTICIPATED MEAN LONG WAVE PATTERN DURING THE FIRST HALF OF APRIL. THE BELOW MEDIAN PRECIPITATION AREA ACROSS THE CENTER PART OF THE COUNTRY WAS SHIFTED TO THE SOUTHWEST TO BE BETTER ALIGNED WITH THE LATEST DYNAMICAL MODEL GUIDANCE.

INDICATIONS OF A WET APRIL ACROSS PARTS OF THE SOUTHWEST AND BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST HAVE DISSIPATED IN MODEL GUIDANCE AND THESE AREAS ARE REMOVED IN THE UPDATED OUTLOOK.“

Let us take a look at today’s 8-14 Day Outlook and compare it to the updated April Outlook Issued today.

Here is the April Temperature Outlook issued today March 31, 2015.

And here is the 8 – 14 Day Temperature Outlook issued today March 31, 2015

I guess you can see how they relate. Remember that the 8 – 14 day outlook only covers 9 days not the full month.

Here is updated Precipitation Outlook for April issued today March 31, 2015

Here is the 8 – 14 Day Precipitation Outlook issued today March 31, 2015.

And again I think you can see how they fit and please remember that the 8 – 14 Day Outlook only covers 9 days.

And here are excerpts from the NOAA release today March 31, 2015.

“6-10 DAY OUTLOOK FOR APR 06 – 10 2015

TODAY’S MODELS ARE IN GOOD AGREEMENT ON THE EXPECTED MEAN 500-HPA HEIGHTS FOR THE 6-10 DAY PERIOD. MODELS PREDICT A BROAD TROUGH WITH AN AXIS LOCATED NEAR THE WEST COAST OF THE CONUS. A WEAK RIDGE IS PREDICTED BY ALL MODELS OVER THE SOUTHEASTERN CONUS WITH A TROUGH LOCATED OVER EASTERN QUEBEC AND THE CANADIAN  MARITIME PROVINCES. A STRONG PACIFIC JET IS FORECAST OVER AND JUST SOUTH OF THE ALEUTIANS WITH MOST OF ALASKA FORECAST TO BE UNDER A 500-HPA TROUGH. THE 06Z GEFS MEAN WAS SLIGHTLY FAVORED IN TODAY’S BLEND BECAUSE ITS SOLUTION BETTER AGREES WITH THE CANADIAN ENSEMBLES OVER THE WEST COAST. THIS SOLUTION FAVORS A  WEAKLY SPLIT FLOW OVER THE WEST COAST, RATHER THAN THE MORE PHASED TROUGH  PREDICTED BY THE ECMWF.  

THE FORECAST RIDGE OVER THE EASTERN CONUS ELEVATES THE CHANCES FOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE EASTERN AND CENTRAL CONUS. TEMPERATURES NEAR THE  MID-ATLANTIC STATES ARE UNCERTAIN DUE TO THE POSSIBILITY OF BACK-DOOR COLD  FRONTS PUSHING COOL AIR FROM NEW ENGLAND AND EASTERN CANADA SOUTHWARD. SURFACE TEMPERATURES FROM THE MODELS SHOW A STRONG TEMPERATURE GRADIENT BETWEEN  BELOW-NORMAL TEMPERATURES FAVORED IN NEW ENGLAND AND ABOVE-NORMAL TEMPERATURES  FAVORED IN THE SOUTHEAST CONUS. NEAR- TO BELOW-NORMAL TEMPERATURES ARE FAVORED  FOR MUCH OF THE WEST NEAR THE EXPECTED WEST COAST TROUGH. TODAY’S MODELS ARE IN  BETTER AGREEMENT THAN YESTERDAY’S FOR NEAR- TO BELOW-NORMAL TEMPERATURES FOR  MUCH OF ALASKA, WITH THE CHANCES FOR ABOVE-NORMAL TEMPERATURES SLIGHTLY  ENHANCED ALONG THE SOUTHERN COAST WHERE SEA SURFACE TEMPERATURES REMAIN ABOVE  NORMAL.   

THE OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR MUCH OF THE EASTERN  CONUS IN EXPECTED SOUTHWESTERLY FLOW AHEAD OF THE WESTERN TROUGH, WHICH WILL ALLOW NORTHWARD TRANSPORT OF MOISTURE FROM THE GULF OF MEXICO. THE CHANCES OF ABOVE-MEDIAN PRECIPITATION ARE ELEVATED NEAR THE WEST COAST FROM THE CENTRAL CALIFORNIA COAST TO THE PACIFIC NORTHWEST NEAR THE EXPECTED WESTERN TROUGH.  BECAUSE THE PACIFIC JET IS PREDICTED TO WEAKEN AS IT APPROACHES THE WEST COAST  OF NORTH AMERICA, THE AREA OF ENHANCED CHANCES OF ABOVE-MEDIAN PRECIPITATION  EXTENDS ONLY SLIGHTLY INLAND, WITH BELOW-MEDIAN PRECIPITATION FAVORED FARTHER  INLAND FROM THE SOUTHWEST TO THE NORTHERN HIGH PLAINS. MOST TOOLS FAVOR  ABOVE-MEDIAN PRECIPITATION FOR SOUTHERN AND CENTRAL ALASKA NEAR AND JUST NORTH 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  GOOD AGREEMENT AMONG MODEL ENSEMBLES AND GOOD AGREEMENT AMONG TEMPERATURE AND  PRECIPITATION TOOLS.

8-14 DAY OUTLOOK FOR APR 08 – 14 2015 

THE PREDICTED 500-HPA CIRCULATION FOR WEEK-2 IS VERY SIMILAR TO THE 6-10 DAY FORECAST, WITH NO SUBSTANTIAL CHANGES IN ANY OF THE UPPER LEVEL FEATURES.  MOSTLY ZONAL 500-HPA FLOW AND A WEAK RIDGE OVER THE EASTERN CONUS ELEVATE  CHANCES FOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE EASTERN AND CENTRAL CONUS, ALTHOUGH BELOW-NORMAL TEMPERATURES ARE SLIGHTLY FAVORED OVER PARTS OF  THE NEW ENGLAND DUE THE POSSIBILITY OF COLD AIR ASSOCIATED A TROUGH FORECAST  OVER EASTERN CANADA. TEMPERATURES IN THE WESTERN CONUS ARE SOMEWHAT UNCERTAIN DUE TO THE UNCERTAIN AMPLITUDE OF THE TROUGH PREDICTED OVER THE WEST COAST.  TEMPERATURES BASED ON CALIBRATED FORECASTS OF NEAR-SURFACE MODEL TEMPERATURES  SLIGHTLY FAVOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE WEST, IN SPITE OF THE BELOW NORMAL UPPER-LEVEL HEIGHTS FORECAST NEAR THE WESTERN TROUGH. THE LACK OF SNOW COVER MAY HELP ELEVATE CHANCES FOR ABOVE NORMAL TEMPERATURES IN HIGHER TERRAIN, AND ABOVE-NORMAL SEA-SURFACE TEMPERATURES MAY ENHANCE CHANCES FOR  ABOVE-NORMAL TEMPERATURES IN ALONG THE COAST IN THE PACIFIC NORTHWEST AND  SOUTHERN CALIFORNIA.  NEAR-NORMAL TEMPERATURES ARE FAVORED ELSEWHERE IN THE WEST. TEMPERATURES HAVE BEEN REVISED TOWARD COOLER TEMPERATURES RELATIVE TO YESTERDAY’S 8-14 DAY OUTLOOK IN ALASKA DUE TO INCREASING AGREEMENT AMONG MODELS ON A FAIRLY DEEP TROUGH OVER THE STATE. THE CHANCES OF BELOW-TEMPERATURES ARE  ELEVATED IN TODAY’S OUTLOOK IN MOST OF ALASKA EXCEPT ALONG THE SOUTH COAST WHERE NEAR-NORMAL TEMPERATURES ARE FAVORED, AND ALONG THE PANHANDLE WHERE ABOVE NORMAL SEA SURFACE TEMPERATURES MAY ENHANCE CHANCES OF ABOVE-NORMAL TEMPERATURES IN COASTAL AREAS. 

THE PRECIPITATION OUTLOOK IS QUITE SIMILAR TO THE 6-10 DAY OUTLOOK, WITH  ABOVE-MEDIAN PRECIPITATION AMOUNTS FAVORED THROUGHOUT MUCH OF THE EASTERN AND  EAST-CENTRAL CONUS, AND BELOW-MEDIAN PRECIPITATION FAVORED FROM PARTS OF THE SOUTHWEST CONUS THROUGH THE NORTHERN GREAT PLAINS. ABOVE-MEDIAN PRECIPITATION  AMOUNTS ARE FAVORED ALONG MUCH OF THE WEST COAST ASSOCIATED WITH THE WESTERN TROUGH. THE GEFS PRECIPITATION FORECAST INDICATES ABOVE-MEDIAN PRECIPITATION  FOR THE SOUTHWESTERN CONUS, CONTRADICTED BY THE ECMWF, SUGGESTING UNCERTAINTY  FOR PRECIPITATION OVER THE DESERT SOUTHWEST. A TROUGH PREDICTED OVER WESTERN  ALASKA ELEVATE THE CHANCES FOR ABOVE-MEDIAN PRECIPITATION FOR WESTERN AND SOUTHERN PARTS OF THE STATE.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 OUT OF 5, DUE  TO GOOD MODEL AND TOOL AGREEMENT, OFFSET BY UNCERTAINTY IN MUCH OF THE WEST DUE TO INCONSISTENT INDICATIONS FOR BOTH TEMPERATURE AND PRECIPITATION AMONG SOME TOOLS.”

Conclusions:

NOAA calls them Outlooks but normal people call them Forecasts. A characteristic of reality is that it will make its presence known. By trade I am a Management Consultant and clients always know more about their business than the consultant. So the consultant uses tricks often described as borrowing the client’s watch, telling them the time, and then sending them an invoice. One trick is looking for incorrect assumptions. If the assumption is incorrect, the conclusion may also be incorrect but it is not always the case for a variety of reasons. The assumption by NOAA that we were having a Traditional El Nino was been an incorrect assumption all winter. It is not just that the intensity has been so marginal that to consider it an El Nino is stretching the definition to the point where the label no longer has much of an impact on forecasts, but also the type of El Nino has not (up until very recently) fallen into the category of being a Traditional Warm Event. Thus forecasting based on that assumption raised the risk of an incorrect forecast. The shorter-term forecasts including the 6 -14 Day Outlook to a very large extent did not depend on that assumption so they have been better grounded.

I issued this Special Edition today because it did not seem right to make everyone wait until next Monday when NOAA issued an update one day after my regular Monday Report. I hope this is useful information.