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FXUS07 KWBC 201231
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU JUN 20 2024
30-DAY OUTLOOK DISCUSSION FOR JULY 2024
IN CONSTRUCTING THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR THE CONTIGUOUS
U.S. (CONUS) AND ALASKA (AK) FOR JULY 2024, WE FIRST EXAMINE THE EQUATORIAL
PACIFIC. SEA SURFACE TEMPERATURE (SST) ANOMALIES HAVE TRENDED TOWARD EL NIñO
SOUTHERN OSCILLATION (ENSO) NEUTRAL CONDITIONS, WITH NIñO3.4 ANOMALIES NEAR 0
DEG C. IN THE EASTERN PACIFIC, BOTH SURFACE AND SUBSURFACE HEAT ANOMALIES ARE
NOW NEGATIVE, SUPPORTING THE LIKELY DEVELOPMENT OF LA NIñA CONDITIONS AS THE
SUMMER PROGRESSES. THE MADDEN-JULIAN OSCILLATION (MJO) IS CURRENTLY
DISORGANIZED AND MOST DYNAMICAL MODEL ENSEMBLE GUIDANCE FORECASTS IT TO REMAIN
INCOHERENT THROUGH THE REMAINDER OF JUNE. EVEN IF ENSO AND MJO FORCING WERE
FORECAST TO BE STRONG, IT IS TYPICAL IN SUMMERTIME FOR THEIR TELECONNECTIONS TO
BE LESS ROBUST DUE TO THE NORTHWARD DISPLACEMENT AND WEAKENING OF THE
SUBTROPICAL JET WHICH LEADS TO A DIMINISHED ROSSBY WAVE SOURCE. THUS, FOR THIS
OUTLOOK, NEITHER ENSO NOR THE MJO PLAY A SUBSTANTIAL ROLE.
INSTEAD, WE TURN TOWARD EXTRATROPICAL FORCINGS SUCH AS COASTAL SST ANOMALIES,
SOIL MOISTURE ANOMALIES, AND THE LONG-TERM TREND. COASTAL SST ANOMALIES ARE
CURRENTLY NEGATIVE ALONG THE WESTERN AND SOUTHERN COASTS OF AK. NEAR CONUS,
THEY ARE ALSO NEGATIVE ALONG THE WEST COAST WHILE THEY ARE POSITIVE ALONG THE
EAST COAST AND GULF COAST. AN INSPECTION OF CURRENT SOIL MOISTURE ANOMALIES AND
NEXT WEEK’S EXPECTED RAINFALL INDICATES AN ENHANCED LIKELIHOOD OF A BROAD SWATH
OF BELOW NORMAL SOIL MOISTURE CONDITIONS STRETCHING FROM THE SOUTHERN PLAINS TO
THE MID-ATLANTIC AND FROM THE LOWER GREAT LAKES TO THE SOUTHEAST. ABOVE NORMAL
SOIL MOISTURE ANOMALIES ARE ANTICIPATED IN SOUTHERN TEXAS AND THE UPPER
MISSISSIPPI VALLEY WHERE HEAVY RAINFALL IS FORECAST OVER THE NEXT WEEK.
LONG-TERM PRECIPITATION TRENDS ARE TOWARD DRIER CONDITIONS IN WESTERN CONUS AND
TOWARD WETTER CONDITIONS ALONG THE MID-ATLANTIC AND NEW ENGLAND DURING JULY.
THE LONG-TERM TEMPERATURE TREND IS POSITIVE EVERYWHERE IN CONUS AND AK.
A SURVEY OF THE DYNAMICAL MODELS (ECMWF, GEFSV12, CFSV2, AND MULTI-MODEL SUITES
FROM THE NMME AND C3S) REVEALS A STRONG CONSISTENCY WITH THE EXTRATROPICAL
FORCINGS ALONG WITH A STRONG AGREEMENT AMONGST EACH OTHER. THUS, THE CONFIDENCE
LEVEL FOR THE JULY 2024 OUTLOOK, INCLUDING BOTH SPATIAL COVERAGE AND THE
STRENGTH OF THE PROBABILITIES, IS RELATIVELY HIGH. AS WE ENTER JULY, THE
DYNAMICAL MODELS DEPICT ABOVE NORMAL 500-HPA HEIGHTS CENTERED OVER THE EAST,
WITH NEAR NORMAL HEIGHTS OVER AK AND THE PACIFIC NORTHWEST. THERE IS SOME
INDICATION THAT THE CENTER OF ABOVE NORMAL HEIGHTS WILL TRANSITION WESTWARD
DURING THE MONTH TO BECOME MORE LOCATED OVER THE INTERMOUNTAIN WEST.
FOR AK, THE TEMPERATURE OUTLOOK IS FOR ELEVATED ODDS OF BELOW NORMAL
TEMPERATURES OVER THE SOUTHWEST MAINLAND AND ALEUTIANS WHERE COASTAL SSTS ARE
BELOW NORMAL AND HEIGHT ANOMALIES INDICATE THE PRESENCE OF NORTHWESTERLY FLOW.
ABOVE NORMAL TEMPERATURES ARE FAVORED ALONG THE EASTERN PORTIONS OF THE NORTH
SLOPE, SUPPORTED BY STRONG LONG-TERM TRENDS IN THAT REGION. PRECIPITATION
ANOMALIES ARE CONSISTENT WITH THE TEMPERATURE OUTLOOK, WHERE ABOVE NORMAL
PRECIPITATION IS FAVORED OVER MOST OF AK WITH THE EXCEPTION OF THE SOUTHERN
COAST WHERE OFF-SHORE FLOW MAY DOMINATE.
FOR CONUS, ABOVE NORMAL TEMPERATURES ARE BROADLY FAVORED WITH TWO CENTERS OF
70-80% PROBABILITIES FEATURED OVER THE MID-ATLANTIC AND THE ROCKIES. THE
MID-ATLANTIC IS EXPECTED TO BEGIN JULY UNDER STRONG MID-LEVEL RIDGING AND BELOW
NORMAL SOIL MOISTURE ANOMALIES, WHICH SHOULD LEAD TO ABOVE NORMAL TEMPERATURES
IN THE REGION. AS THE RIDGE RETROGRADES WESTWARD, ABOVE NORMAL TEMPERATRURES
ARE LIKELY IN THE ROCKIES. ODDS FOR ABOVE NORMAL TEMPERATURES ARE CONSIDERABLY
LOWER IN THE PACIFIC NORTHWEST, COASTAL CALIFORNIA, THE UPPER MISSISSIPPI
VALLEY, AND PORTIONS OF TEXAS. IN THE PACIFIC NORTHWEST, EQUAL CHANCES (EC) OF
ABOVE, NEAR, OR BELOW NORMAL TEMPERATURES IS FORECAST DUE TO THE EXPECTED
TROUGHING TO BEGIN THE MONTH OF JULY. OVER COASTAL CALIFORNIA, EC IS ALSO
FAVORED DUE TO THE BELOW NORMAL COASTAL SSTS LEADING TO THE POSSIBILITY OF AN
ENHANCED SEA BREEZE. IN THE UPPER MISSISSIPPI VALLEY, POSITIVE SOIL MOISTURE
ANOMALIES AND A RELATIVELY WEAKER LONG-TERM TREND LOWER THE ODDS OF ABOVE
NORMAL TEMPERATURES. ABOVE NORMAL SOIL MOISTURE ANOMALIES ALSO LEAD TO LOWERED
PROBABILITIES OF ABOVE NORMAL TEMPERATURES IN TEXAS.
THE PRECIPITATION OUTLOOK OVER CONUS IS LESS CONFIDENT THAN THE TEMPERATURE
OUTLOOK, WHICH IS TYPICAL DURING THE SUMMER MONTHS DUE TO THE STOCHASTIC NATURE
OF CONVECTION AND THE UNCERTAINTY OF ANY IMPACTS FROM TROPICAL CYCLONES.
NEVERTHELESS, GIVEN THE EXPECTED POSITIVE HEIGHT ANOMALIES AND RELATIVELY
DECENT MODEL AGREEMENT, BELOW NORMAL PRECIPITATION IS FAVORED OVER MOST OF THE
NORTHERN TWO THIRDS OF CONUS. HIGHER PROBABILITIES ARE CENTERED OVER THE OHIO
VALLEY AND INTERMOUNTAIN WEST, IN AGREEMENT WITH THE TEMPERATURE OUTLOOK, THE
EXPECTED PLACEMENT OF 500-MB HEIGHT ANOMALIES, AND DRY SOIL CONDITIONS IN THE
EAST. A THIN BAND OF EC WAS MAINTAINED ALONG THE EAST COAST DUE TO POSITIVE
LONG-TERM TRENDS, AND, WHILE AN OUTLIER, THE ECMWF IS FORECASTING ABOVE NORMAL
PRECIPITATION ALONG THE EAST COAST. OVER THE DESERT SOUTHWEST, MOST DYNAMICAL
MODEL GUIDANCE IS FORECASTING A WEAKER SOUTHWEST MONSOON, LEADING TO ENHANCED
BELOW NORMAL PROBABILITIES THERE. FINALLY, ABOVE NORMAL PRECIPITATION IS
FAVORED ALONG THE GULF COAST STATES, AS FORECAST BY MOST DYNAMICAL MODELS AND
SUPPORTED BY THE EXPECTED ABOVE NORMAL TROPICAL CYCLONE ACTIVITY THIS YEAR.
FORECASTER: CORY BAGGETT
THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1991 AND 2020, FOLLOWING
THE WORLD METEOROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3
COMPLETE DECADES AS THE CLIMATE REFERENCE PERIOD. THE PROBABILITY ANOMALIES
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS.
AN UPDATED MONTHLY OUTLOOK... FOR JUL WILL BE ISSUED ON SUN JUNE 30 2024
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
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