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Prognostic Discussion for Monthly Outlook
NWS Climate Prediction Center College Park MD
830 AM EST Thu Feb 15 2024
30-DAY OUTLOOK DISCUSSION FOR MARCH 2024
A number of climate factors are considered in preparing the March 2024
temperature and precipitation outlooks. In addition to the ongoing, albeit
weakening El Nino, an ongoing MJO event continues. To further complicate
matters, there are indications of a weakening in the stratospheric polar vortex
potentially leading to a Sudden Stratospheric Warming (SSW) sometime during the
second half of February. Moreover, El Nino wintertime residual impacts are also
considered in developing the outlook.
Even though El Nino oceanic conditions have peaked - SSTs are decreasing and
oceanic heat content along the equator with depth in the Pacific basin has
decreased considerably, the induced atmospheric response can often linger and
so common El Nino impacts are likely to continue at times through March and
potentially into April. So the March 2024 temperature and precipitation
outlooks continued to consider El Nino as part of the large scale base state
and so potential impacts.
The MJO has been quite active the last several weeks, but its current coherency
is being impacted by multiple modes of both subseasonal [i.e., atmospheric
Kelvin waves and Equatorial Rossby waves (KW/ERW)] and inter-annual forcing
(i.e. ENSO). With this the cas e, some standard realtime metrics of the MJO
amplitude and phase are disturbed and at times less clear when monitoring. But
given recent Pacific Ocean jet strength and extensions and monitoring the
circulation only portion of the signal (e.g., 200-hPa velocity potential) it
appears the MJO remains active and has entered and is crossing western
Hemisphere. Model predictions of the RMM index, vary highly, but most generally
favor continue eastward propagation of a signal across Africa back towards the
Indian Ocean over the next couple of weeks. If this becomes the cas e and
enhanced convection redevelops in the eastern Indian Ocean and Maritime
Continent, ridging and above-normal temperatures for the eastern half of the
CONUS would tend to be favored. Weak signals or troughing would be most likely
at modest odds across the western CONUS.
Recent monitoring of the stratosphere and model predictions of the 10-hPa zonal
wind indicate a potential for a SSW and potential coupling with the troposphere
and a tendency to favor a negative AO for periods during the month of March.
However, there remains high uncertainty in the eventual evolution after any SSW
event and so follow on -AO potential. Even with a SSW event, there always
remains considerable variability in how the vortex is impacted (i.e. displaced
vortex vs. a split vortex) and the hemisphere (eastern vs. western) where the
odds are the greatest for more frequent Arctic air outbreaks during March.
In mid-February, substantial snow deficits are evident from the northern High
Plains eastward to the Great Lakes and Northeast - common after El Nino
winters. Increased wetness and snowpack has developed in recent weeks for
portions of the western CONUS primarily in California, Nevada, and the central
and southern Rockies as a result of active Pacific storminess.
Weighing all these factors, the March 2024 temperature outlook favors
above-normal temperatures for much of the Far West, Pacific Northwest eastward
across the northern Plains, Great Lakes and for much of the eastern CONUS. El
Nino and negative snow departures support the forecast for much of this
highlighted area. Potential MJO influence supports the extension of favored
above-normal warmth for the eastern third of the CONUS. Lower odds for
above-normal temperatures in the northern Plains and western Great Lakes, large
area of Equal-Chances (EC) in the interior of the CONUS and slightly favored
below-normal temperatures for parts of the Southeast and Texas are in deference
to potential influence from negative AO periods. Elevated odds for above-normal
precipitation also contributes slightly to the below-normal temperature
forecast in this region. Potential troughing associated with the MJO and
elevated chances for above-normal precipitation in some areas support a slight
tilt toward below-normal temperatures for parts of the Southwest. Above-normal
temperatures are most likely for the entire state of Alaska.
For precipitation, El Nino background conditions and potential MJO influence at
times in March, favor above-normal monthly total precipitation amounts from
California eastward across the central Rockies to the north-central Plains.
Dynamical model guidance (NMME, C3S) and long term positive precipitation
trends also support this forecast. El Nino considerations and dynamical model
guidance support elevated odds for above-normal precipitation for the Gulf
Coast, the Southeast and much of the eastern seaboard as well as smaller
regions of favored below-normal precipitation for parts of the Pacific
Northwest and central Great Lakes. The majority of dynamical model guidance
favored below-normal monthly precipitation amounts for southern Texas. For
Alaska, above-normal precipitation is most likely for most of the southern
portion of the state.
FORECASTER: Jon Gottschalck
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 Mar will be issued on Thu February 29 2024
These outlooks are based on departures from the 1991-2020 base period.