Atmospheric patterns, 700 MB and 500 MB height anomalies, statistical data, and various models such as the ECMWF monthly and weekly, NMME, IMME and the CFSv2, along with observed cases from past such months, data from 1895-2000 were used in this forecast.
During February 2024, sea surface temperature anomalies continued to weaken across most of the equatorial Pacific Ocean. In the last week, below-average sea surface temperatures emerged in a small region of the eastern equatorial Pacific Ocean in the area of 100°W). The weekly Niño indices weakened but remained positive, with the latest value in Niño-3.4 standing at 1.4°C. Area-averaged subsurface temperature anomalies were slightly negative, reflecting the consequences of an upwelling Kelvin wave and associated below-average temperatures across the equatorial Pacific Ocean [Fig. 4]. Low-level winds were near normal over most of the equatorial Pacific, while upper-level wind anomalies were easterly over the east-central Pacific. Convection was enhanced near the Date Line and was suppressed near Indonesia. Collectively, the coupled ocean-atmosphere system reflected a weakening El Niño.
The most recent IRI plume indicates a transition to ENSO-neutral during spring 2024, with La Niña potentially developing during summer 2024.
In summary, a transition from El Niño to ENSO-neutral is likely by April-June 2024, with the odds of La Niña developing by June-August 2024.
The large-scale circulation pattern, the manual blend of dynamical and statistical guidance indicates broad anomalous ridging across Canada and anomalous troughing across the southern tier of the CONUS, a continuation of the Week-2 pattern. However, there is some uncertainty in this pattern as agreement among the individual dynamical models are mixed, particularly on the extent of the troughing. In particular, the CFS solution confines the anomalous troughing the East Coast, and the ECMWF favors weak anomalous ridging. Much of the disagreement is related to the evolution of this pattern during the Week 3-4 period.
The predicted pattern across North America will feature a trough across western North America forcing strengthening ridge across eastern North America.
Robust climate signals continue to dominate the tropical Pacific characterized by the consistent albeit weakening El Niño signal and the strong Madden Julian Oscillation propagation. The MJO-related convection is currently in the western Pacific, associated with Phase 7 of Real-time Multivariate MJO (RMM) indices , and is forecast to continue its eastward propagation for at least the next week. The Arctic Oscillation is neutral, but models forecasts indicate a trend toward a slightly negative AO in the next two weeks. This transition could further be reinforced by the current MJO phase as well as the ongoing major sudden stratospheric warming. The negative AO is often associated with the below normal temperatures across CONUS, though less impactful during this time of year. These climate signals are taken into account when interpreting the model guidance for this week's forecast.
The ECMWF weeklies depict a ridge between Hawaii and Alaska, a trough across western North America and across the nation with a ridge across Greenland for week-1. The flow transitions to a zonal flow with above-normal heights across North America thereafter. The Subx ensembles means depict above-normal heights across the nation. The C3S is similar.
The ECMWF weeklies depict below-normal temperatures in the West and above normal temperatures in the East for week-1. Above-normal temperatures and then expected to be above normal across the nation foe week2-4. The Subx depict above-normal temperatures across much of the nation and below normal temperatures for the Southeast. The C3S depicts above normal temperatures across the nation.
TEMPERATURES
Yeloow-2-4°F
Orange-4-6°F
Red-6-8°F or Greater
Mediam Blue 4-6F Below
Dark Blue-6-8F or Great Below
Above-normal temperatures are forecast west of the Divide. Anomalies of up to 4-8°F are possible. Below-normal temperatures are forecast for the southern Plains. Anomalies of 2-4°F are expected. The remainder of the nation is not expected to exceed normal climatology.
PRECIPITATION
Yellow=-35%
Below
Brown-35-45% Below
Dark
Brown-45-55% Below
Light
Green-30-35% Above
Green-35-45% Above
Dark
Green-45-55%Above
Above-normal precipitation is forecast for the Northwest into the Great Basin and the eastern Plains to the Atlantic Coast. The probability of occurrence is near 35 percent. The remainder of the nation is not expected to exceed normal climatology.
Jim Munley Jr.
http://www.jimmunleywx.com/jimmunleywx
Forecast Verification