After eight months with temperatures in the equatorial Pacific below normal that gave rise to the cold phase of ENSO, this May 2021 La Niña was declared over. Next, upcoming weather conditions for our country will be mentioned.
During the last weeks, we have had a welcome increase in rainfall over several entities, the entry of a cold front and decreases in temperatures, in addition to extreme hail events in Nueva Rosita and Piedras Negras, Coah., Tornadoes in sectors of Hidalgo, and possibly also Coahuila – Tamaulipas, as well as extreme rains in Xalapa, Ver., Reynosa, Tamps., and other locations in Oaxaca, Chiapas and Campeche, as well as heat above 45 ° C in Sinaloa, San Luis Potosí, among others, typical of a month of May.
The report issued by the Climate Predictions Center (CPC) on Thursday, May 13, indicated the weakening of the La Niña phenomenon, returning to normal anomalies between -0.7 and -0.1 ° C throughout the regions. of El Niño, while the winds weakened, all this indicating the end of the cold phase, La Niña, now transitioning to a neutral phase. The waters below the surface are warmer than normal, which may continue to emerge in the coming weeks.
The dynamic-statistical forecast assemblies, although they still have uncertainty, it is observed: probable continuation of neutral conditions in summer and autumn up to 73%, decreasing as autumn towards winter, being probable a transition again towards La Niña with a potential of 50 -55%, with the probability for an El Niño event being almost nil this year. However, the “spring barrier” is still active, so we have to wait a little longer to secure a scenario. ENSO’s current neutral phase can help rains increase and spread in Mexico, while cyclonic activity normalizes. We will have to be vigilant in case La Niña returns …
Each ENSO event is unique, but when the neutral condition is established, the meteorological and climatic behavior becomes very uncertain as well-established meteorological patterns are not observed. Under this neutral situation, it can be mentioned that the rains can increase and spread in Mexico due to the passage of waves/tropical cyclones and the activation of the Monsoon. This could help the drought to slow down and, in the best of cases, tend to noticeably decrease its extension, but it will be more likely if a cyclone enters.
Weather trend for the following weeks
During this second fortnight of May, more rains than normal are expected in states of the northeast, center, and part of the east-southeast, due to convective storm systems (possible squalls) and the entry of humidity from the Caribbean, Gulf of Mexico and Pacific. being latent the probability of severe events with hail and tornadoes. On the other hand, the temperatures would be within or lower than the climatology, that is, a less hot environment.
Some models show the possible activation of the Central American Giro, an extensive cyclonic system that commonly occurs in June with significant rains in southeastern Mexico and Central America, from where tropical cyclones can emerge. Although it cannot be assured yet, it will be necessary to be aware of these possible effects.
During June the rain potential would increase notably in much of the Mexican Republic, highlighting the center, west, and much of the north. Yes and only if, a trend of neutral phase to La Niña is observed towards autumn, tropical cyclones in the Atlantic may increase, decreasing in the Pacific, so the rain patterns would be reversed to be rainier in the east and southeast, as well as sectors of the center-south, decreasing in the northwest and west, the incidence of cold fronts beginning to be higher.