389
FXUS07 KWBC 301900
PMD30D
PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SUN JUN 30 2024
30-DAY OUTLOOK DISCUSSION FOR JULY 2024
THE UPDATED JULY 2024 TEMPERATURE AND PRECIPITATION OUTLOOKS FOR THE CONTIGUOUS
U.S. (CONUS) AND ALASKA (AK) TAKE INTO ACCOUNT THE MOST RECENTLY OBSERVED
PHYSICAL DRIVERS AND THE LATEST INITIALIZATIONS FROM THE ENSEMBLE SUITES OF THE
DYNAMICAL MODELS (ECMWF, GEFSV12, GEM, CFSV2, AND JMA).
NEITHER EL NIñO SOUTHERN OSCILLATION (ENSO) NOR THE MADDEN-JULIAN OSCILLATION
(MJO) ARE EXPECTED TO HAVE A MEANINGFUL IMPACT ON THE EVENTUAL TEMPERATURE AND
PRECIPITATION OUTCOME OVER CONUS AND AK. NIñO3.4 ANOMALIES INDICATE ENSO
NEUTRAL CONDITIONS, ALTHOUGH 200-HPA VELOCITY POTENTIAL ANOMALIES ARE BEGINNING
TO RESEMBLE A LA NIñA BACKGROUND STATE WITH ENHANCED DIVERGENCE OVER THE
MARITIME CONTINENT AND CONVERGENCE FARTHER EAST. THE MJO IS CURRENTLY WEAK,
WITH ANY REMAINING SIGNAL INDICATING THE CONVECTIVELY ACTIVE PHASE OVER THE
INDIAN OCEAN. SOME ENSEMBLE SUITES OF THE DYNAMICAL MODELS FORECAST A
STRENGTHENING MJO PROPAGATING TO THE MARITIME CONTINENT. HOWEVER, CONVECTION IN
THIS REGION WOULD ALSO BE CONSISTENT WITH AN EMERGING LA NIñA. REGARDLESS, THE
NORTHERN HEMISPHERE EXTRATROPICAL TELECONNECTIONS TO ANOMALOUS TROPICAL
CONVECTION ARE WEAK DURING JULY.
IN THE EXTRATROPICS, SEA SURFACE TEMPERATURE (SST) AND SOIL MOISTURE ANOMALIES
REMAIN LARGELY UNCHANGED FROM THE ORIGINAL OUTLOOK. NAMELY, BELOW NORMAL
COASTAL SSTS ARE STILL OBSERVED ALONG THE WESTERN COAST OF ALASKA AND THE WEST
COAST, PARTICULARLY NEAR CALIFORNIA. ABOVE NORMAL COASTAL SSTS ARE FOUND ALONG
THE GULF COAST AND EAST COAST. SOIL MOISTURE ANOMALIES ARE STRONGLY POSITIVE IN
THE UPPER MISSISSIPPI VALLEY. THEY ARE NEGATIVE FROM THE CENTRAL PLAINS TO THE
MID-ATLANTIC. SOILS ARE BECOMING INCREASINGLY DRY ACROSS SOUTHERN OK AND
NORTHERN TEXAS. DESPITE HEAVY RAINS EARLIER IN JUNE, THE RECENT ~3 WEEKS HAVE
BEEN VERY DRY ALONG THE RED RIVER VALLEY.
SIGNIFICANT UPDATES TO THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR JULY ARE
LARGELY RELATED TO SHORT TERM MODEL OUTPUT FOR WEEK 1, WHICH TYPICALLY HAS HIGH
FORECAST SKILL. THE OVERALL 500-HPA HEIGHT PATTERN DURING WEEK 1 FEATURES VERY
STRONG RIDGING DEVELOPING ALONG THE WEST COAST, TRANSIENT TROUGHING IN THE
NORTHERN PLAINS, AND DOWNSTREAM RIDGING OVER THE EAST COAST. THIS PATTERN
DIFFERS FROM MODEL INITIALIZATIONS LAST WEEK, WHICH FAILED TO PREDICT THE RIDGE
ALONG THE WEST COAST AND THE DEPTH OF THE TROUGH IN THE NORTHERN PLAINS. OVER
AK, RIDGING IS EXPECTED OVER THE SOUTHERN HALF OF THE STATE AND TROUGHING IS
ANTICIPATED ALONG THE NORTH SLOPE. THIS PATTERN LEADS TO A MOIST ONSHORE FLOW
FROM THE BERING STRAIT. AS THE MONTH OF JULY PROGRESSES INTO WEEKS 2, 3, AND 4,
THE TROUGHING IN THE NORTHERN PLAINS IS FORECAST TO DIMINISH; THE RIDGE ALONG
THE WEST COAST IS EXPECTED TO MOVE MORE INLAND, BECOMING MORE CENTERED OVER THE
NORTHERN ROCKIES; AND THE PATTERN OVER ALASKA LOOKS TO PERSIST.
THE UPDATED TEMPERATURE OUTLOOK REFLECTS THE RIDGE AXIS PREDOMINANTLY RESIDING
OVER WESTERN CONUS WITH THE HIGHEST PROBABILITIES FOR ABOVE NORMAL TEMPERATURES
REACHING 70 TO 80% OVER THE GREAT BASIN, SOUTHWEST, AND INTERMOUNTAIN WEST. IN
FACT, TEMPERATURES OVER CALIFORNIA DURING WEEK 1 ARE FORECAST TO BE EXCESSIVELY
HOT, WHICH HAS NECESSITATED THE REMOVAL OF ANY EQUAL CHANCES (EC) OF ABOVE-,
NEAR-, OR BELOW-NORMAL TEMPERATURES ALONG THE CALIFORNIA COAST. THE MUCH ABOVE
NORMAL TEMPERATURES ARE FORECAST TO BUILD NORTHWARD INTO THE PACIFIC NORTHWEST
AS WEEK 1 PROGRESSES, WHICH HAS ALSO LED TO THE REMOVAL OF EC IN THAT REGION.
SOME RELIEF MAY OCCUR ALONG THE IMMEDIATE WEST COAST VIA SEA BREEZE MECHANISMS.
ENTERING WEEK 2, THE RIDGE AXIS IS FORECAST TO MOVE MORE INLAND WHICH WOULD
PUSH TEMPERATURES TO ABOVE NORMAL VALUES IN THE NORTHERN ROCKIES, AFTER A
NEAR-NORMAL OR SLIGHTLY-BELOW NORMAL START TO THE MONTH DUE TO TRANSIENT
TROUGHING IN THE NEIGHBORING NORTHERN PLAINS. IT SHOULD ALSO BE NOTED THAT
LONG-TERM TEMPERATURE TRENDS ARE POSITIVE IN WESTERN CONUS DURING JULY, AND THE
TEMPERATURE OUTLOOK REFLECTS THAT REALITY. IN THE NORTHERN PLAINS AND UPPER
GREAT LAKES, EC IS FORECAST IN THIS UPDATED OUTLOOK DUE TO SOME NEAR- TO
BELOW-NORMAL TEMPERATURES ADVECTING IN FROM THE NORTH DURING WEEK 1 ALONG WITH
ABOVE NORMAL SOIL MOISTURE ANOMALIES. MOST MODELS, INCLUDING THE ECMWF, EXPECT
THE TRANSIENT TROUGHING TO ABATE DURING WEEK 2, ALTHOUGH THE GEFS SHOWS SOME
LINGERING COLDER THAN NORMAL TEMPERATURES. FARTHER SOUTH AND EAST INTO THE
SOUTHERN PLAINS, TEXAS, SOUTHEAST, OHIO VALLEY, MID-ATLANTIC, AND NEW ENGLAND
ELEVATED ODDS OF ABOVE NORMAL TEMPERATURES ARE SUPPORTED BY WARM AIR ADVECTION
DOWNSTREAM OF THE ANTICIPATED TROUGHING IN THE NORTHERN PLAINS, LONG-TERM
TRENDS DURING JULY, AND STRONG MODEL AGREEMENT.
THE UPDATED PRECIPITATION OUTLOOK FEATURES A FEW NOTABLE CHANGES. A DECENT
MOISTURE PLUME DURING THE FIRST WEEK OF JULY IS ANTICIPATED TO PRODUCE
RELATIVELY WIDESPREAD THUNDERSTORM ACTIVITY IN THE DESERT SOUTHWEST. WHILE THIS
ACTIVITY LESSENS DURING WEEK 2, THERE IS SOME INDICATION OF IT RE-EMERGING AS
THE MONTH UNFOLDS. THIS TILTS THE ODDS FROM BELOW NORMAL IN THE ORIGINAL
OUTLOOK TOWARD A BROAD REGION OF EC WITH A SMALL EMBEDDED REGION OF
ABOVE-NORMAL NEAR THE SOUTHERN BORDERS OF NEW MEXICO AND ARIZONA. FARTHER NORTH
IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, BELOW NORMAL PRECIPITATION IS
STILL EXPECTED WITH STRONG RIDGING OVER THE REGION. HOWEVER, SOME MONSOON
MOISTURE CANNOT BE RULED OUT, SO PROBABILITIES FOR BELOW-NORMAL PRECIPITATION
WERE BROADLY LOWERED. ABOVE NORMAL PRECIPITATION IS NOW FAVORED OVER THE UPPER
MISSISSIPPI VALLEY DUE TO HEAVY RAIN ANTICIPATED DURING WEEK 1 AS A RESULT OF
THE TRANSIENT TROUGHING. BELOW NORMAL PRECIPITATION IS FAVORED ALONG THE RED
RIVER VALLEY OF OKLAHOMA AND TEXAS, AS MOST MODELS AGREE THE REGION WILL REMAIN
DRY WITH BELOW NORMAL SOIL MOISTURE ANOMALIES AND NO APPARENT MOISTURE
ADVECTION INTO THE REGION. A THIN SLIVER OF ABOVE NORMAL PRECIPITATION IS
FORECAST ALONG THE GULF COAST, FLORIDA, AND EAST COAST. MODELS ARE MIXED IN
THIS REGION, BUT ULTIMATELY THE LONG TERM TREND AND POTENTIAL TROPICAL ACTIVITY
TILT THE ODDS TO ABOVE NORMAL. WITH RESPECT TO TROPICAL ACTIVITY, IT SHOULD BE
NOTED THAT THE EVENTUAL TRACK OF HURRICANE BERYL IN ADDITION TO DISTURBANCES IN
THE GULF OF MEXICO AND MAIN DEVELOPMENT REGION OF THE ATLANTIC ALL LEAD TO
UNCERTAINTY IN THE CURRENT PRECIPITATION OUTLOOK.
FINALLY, FOR ALASKA, ONSHORE FLOW FROM THE BERING STRAIT IS TYPICALLY A WET AND
COOL PATTERN DURING JULY. THUS, NEARLY ALL OF THE STATE IS FAVORED TO HAVE
BELOW NORMAL TEMPERATURES WITH THE EXCEPTION OF THE EASTERN PORTION OF THE
NORTH SLOPE DUE TO LONG-TERM TRENDS. ABOVE NORMAL PRECIPITATION IS ALSO
EXPECTED OVER THE ENTIRE STATE WITH THE EXCEPTION OF THE PANHANDLE WHERE THE
INFLUENCE OF THE RIDGE ALONG THE WEST COAST RESULTS IN EC BEING FORECAST.
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***** PREVIOUS MID-MONTH DISCUSSION BELOW *****
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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.
THE NEXT MONTHLY OUTLOOK...FOR AUG ... WILL BE ISSUED ON THU JUL 18 2024
THESE OUTLOOKS ARE BASED ON DEPARTURES FROM THE 1991-2020 BASE PERIOD.
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