Warm Water Everywhere

noaa-1-680x380The picture above, courtesy of NOAA/NESDIS, gives the sea surface temperature (SST) “anomaly”, or difference from the normal temperature for the date. In this color scheme, yellows and red are warmer than normal and blues are cooler. It is obvious to even the casual observer that the contiguous U.S. is currently surrounded by water that is warmer than normal. Only far southern California is cooler than normal, and that is connected with some recent upwelling that brought it down from very warm temperatures during the winter.
The band of warm water along the equator in the Pacific is connected to the incipient El Niño, but the connection between all the other warm water and El Niño is less clear. Whatever the cause, these warm oceans evaporate a lot more water into the atmosphere and can fuel hurricanes and other storms. The Eastern Pacific hurricane season got off to one of its fastest starts ever, with Hurricane Andres followed closely by Hurricane Blanca, both of which became category 4 major hurricanes. When Andres struck Baja California June 8th it became the earliest tropical cyclone to strike the peninsula, beating the old record by a full month. Hurricane Blanca moved very slowly at one stage of its life cycle, and may be the reason for the blobs of cooler than normal water seen west of Mexico in the image above. Intense, slow moving tropical cyclones churn up cold water from great depths, and at least temporarily lower the temperature of the surface water.
As the moist air from Blanca pushed northward into the U.S. it caused light rains to fall in Los Angeles and even caused severe thunderstorms with large hail near WeatherExtreme offices in Incline Village. Unfortunately it did little to alleviate the extreme drought in California. Somewhat ironically, San Diego experienced its highest “precipitable water” ever in June, as a result of that moist air, but received almost no rain. Precipitable water measures how much water is present as vapor between the surface and the top of the atmosphere, and is related to the potential for heavy rains. It’s only a potential, though, and if there is no lifting mechanism present then no rain will fall.
In contrast, May brought extremely heavy rains to Texas and Oklahoma and made the month became the rainiest on record in the contiguous U.S. There is a good chance that the unusually warm waters encircling North American contributed to this record rainfall. Unfortunately a new (as yet unnamed) tropical system may once again bring heavy rain to Texas, with 10 inches or more expected in some areas.