Summer 2015 Forecast

    As meteorological summer begins, it is worth looking at what to expect. Of course the big name being thrown around has been El Nino, and that could certainly have an effect on our weather patterns. Although it’s the biggest name, the El Nino is not the only player around that will influence the coming months. I am going to take a look at the possible influences on the summer and break them down.

             

                The El Nino

                SOI (?)

                MJO      

                PDO

    Let’s start with the developing El Nino. Forecasters have been calling for a strong El Nino to form this summer, but so far that has not been the case. Past ENSO (El Nino Southern Oscillation) values, beginning in September 2014, maxed out at +0.7 in October and November, but has since stagnated, if not decreased in strength since then. Values December through March have hung around +0.5-+0.6. For a more definitive El Nino to form these values will have to show a distinct rise, and to fulfill the possibly overblown El Nino forecasts, it would need to reach above +1.0-+1.5. The strong El Nino forecasts have happened before, most recently this past summer and early fall, where forecasters called for a very strong El Nino going into winter, but that never materialized. ENSO values are given over a month after they happen, so the values for April and May are not out yet. If they yield a strong rise in ENSO values, then the strong El Nino forecast may be right, but observations so far are not supporting the idea of high ENSO values.

    This is important to consider because the strength of the El Nino will influence our summer weather, which includes; the tropics, temperature, and precipitation. If the El Nino is as weak as is currently believed, then other factors will have more influence on our summer weather. If the El Nino forms we may be in for a seasonable to cooler than average summer. Precipitation for the Northeast will not be effected significantly by the El Nino this summer. For many the most important portion of an El Nino summer could be a less active Hurricane Season and some drought relief for California.

    If the El Nino weakens any more or does not strengthen the effects will be more negligible, and the summer could be more variable, and other factors, which I will introduce, will be more influential.

    Recent forecasts made by WSI and The Weather Channel are more focused on the SOI values being shown, which are measurements of pressure differences between Tahiti and Darwin, Australia. These fluctuations are a product of ENSO shifts, and thus a forecast referencing these values are more or less references the state of the ENSO. I have spoken about the effects of El Nino on the summer and most likely do not need to go into further detail. I will however provide with the forecast from WSI and The Weather Channel for reference.

    Now for the MJO (Madden–Julian oscillation), this is a gauge of activity across the tropics. As of this moment the MJO has moved into the western hemisphere. This means that tropical energy has shifted into the tropical Atlantic and will be an influence on weather. The MJO moves west to east, and is important for mid to long range forecasts. It will not help us understand what August will be like, but can get us through June and early July. While the increased MJO is around, which it has been for almost two weeks, intense precipitation events are more likely, as there will be more tropical moisture and energy to tap. This has been witnessed in the south and northeast recently, where mist air that originated from the tropics, came up and prepared the stage for hefty amounts of rainfall. As long as the MJO is around, storms packing tropical moisture will be quiet potent.

   Finally, the Pacific Decadal Oscillation, PDO. At the moment the PDO is at .99, and presumably dropping. A lower PDO, although not negative, will hamper the growth of a strong El Nino event, and lead to summer heating across the eastern two thirds of the United States. The PDO has been dropping at an average rate of .18 per month since December, which, it being June, would put us at roughly .81 or lower, assuming it’s a steady drop. This will set up a pattern where the El Nino will struggle to strengthen, and the MJO + PDO will go to work to warm up the country east of the Rockies. Warm and moist air will dominate for a time being, with interspersed moments of cool air as usual.

    In regards to Hurricane season, having the MJO around and warm air, may give life to the tropics, contradicting current forecasts. It is a possibility. I am not making a hurricane season forecast of my own.

Here’s the Run Down

June-

         With the MJO around and a weak El Nino, the Northeast will be warmer than average, with a
heat wave toward the end of the month. Precipitation for the past few months has been below average, but I believe June will erase these deficits.

July-

         The early part of July should be warmer than average, and with continued higher precipitation. From mid-July to the end of July, temperatures should begin to average out.

August-

                  Average temperature, but without the MJO, lower amounts of precipitation. 

*Disclaimer: This is my first ever season forecast. Do with that information what you want*