United States Summer 2015 Forecast

Written by on April 1, 2015 in Summer 2015, United States of America with 0 Comments

This seasonal outlook for the upcoming Summer of 2015 for the United States is based on past and current pattern and influences of current and projected sea surface temperatures and El Nino.

For the past two straight winter seasons, a warmer than normal 2-metre temperature pattern has resided from California across to Arizona up the West side of North America while a colder pattern has dominated the eastern side. This goes for the warm season as well and the primary reason behind this persistent pattern is the well above normal SST’s off the West Coast.

Current global SST’s.

anomnight_3_30_2015

CFSv2 projected SST’s for June-August

glbSSTSeaInd3

Summer 2013 and 2014 was cool and wet in the central and eastern US while above normal in the West. The warmer than normal waters have supported persistent above normal upper level high pressure and this has redirected Pacific storms north which in turn has forced one of the greatest droughts in California in the last 100 years.

The upcoming summer precipitation distribution will be based on current soil moisture content and the projected strengthening of the El Nino.

Here’s the latest US drought monitor map.

Credit: National Drought Mitigation Center

Credit: National Drought Mitigation Center

California & West

Because of the southward extension of ABNORMALLY WARM water down the West Coast, the winter just gone supported even an even warmer winter for California & Southwest compared to 2013-14 with many seeing their driest or warmest winter (both for some) and the fact there’s little to no rain during the June-August period, there’s no reason to think we won’t see another warm if not warmer summer in 2015.

The drought on land and very warm water against the West Coast makes me fear a very long and hot summer lies ahead with frequent heat spells likely.

The typical increase in marine layer in May and June is likely to be suppressed due to warmer than normal waters. Typically, as the land heats late spring/early summer and the cold California current keeps waters offshore nice and cool, there’s a nice thick marine layer which keeps the coast naturally cool but without it, it’s warmer than normal right to the coast. 2006 saw abnormal warm water off the coast, less marine layer May and June and a record breaking heat wave that July. It was also an El Nino year!

Rockies & Plains

Because of the strengthening El Nino and the warm waters up against the coast, this should lead to at or below normal heights further east from the Rockies into the Plains with rainfall likely to be above average during the first half of summer (June-July), however, look at the drought on the Southern Plains and the increasingly dry soils over the Northern Plains. While it may be a somewhat wet spring for the Heartland of the nation, strengthening El Ninos tend to lead to drier and warmer mid to late summers. Remember back to that summer of 2006. Heat was extreme yes but combination of increasing drought on the plains lead to record upper heights and surface heat below with 120F recorded in South Dakota. No, I am not calling for that this year but DO NOT be surprised if July and August gets increasing hot into the western Plains.

Midwest, Ohio & Tennessee Valleys

Because of the upper level setup expected with mean ridging focused up the West Coast into Alaska/NW Canada, a weak negative or trough should reside over the Great Lakes into the Ohio/Tennessee Valleys this summer. I expect the increase in rainfall mid to late spring to have negative influence on mid and upper level heights into at least the first half of the summer (June-July). Wet ground tends to lead to lower heights and increased moisture levels in the atmosphere. This forces a large percentage of the sun’s incoming energy to ne used for evaporation and not heating of the air. 90/95F+ days are likely to be few like in the last two summers.

Because of the Southern Plains drought and dry ground over the Dakotas into Minnesota, heat may try to extend east as El Nino summers tend to be drier and warmer during the second half and this may try extending east late summer into the OH/TN Valleys.

East Coast

While I expect a cooler, wetter second half to spring, warmer than normal waters from Florida to Maine and within the Gulf of Mexico makes me below a warmer than normal summer is likely closest to the Atlantic Seaboard. Warmer than normal SST’s should lead to higher levels of humidity and though a mean neutral or negative height field is expected over the East Coast at least through the first half of summer 2015, the higher humidity should help boost temperatures above normal, especially by night.

Also expect increased chances for East Coast rainstorms and tropical cyclone threats which could temper heat waves and extreme high temperatures this summer.

I believe the CFSv2 has the right idea for the upcoming summer in it’s precipitation and temperature projections.

700mb anomalies reflect the below quite well.

Credit: NOAA

Credit: NOAA

usPrecSeaInd3

usT2mSeaInd3

Jamstec has a much cooler solution.

Credit: Jamstec

Credit: Jamstec

Thanks for reading. Will discuss the above in greater detail in upcoming write-ups and videos.

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