Southeast U.S. Update
Let’s take a look at the current rain event moving across the Southeast U.S. A line of convection is moving slowly east with a northeast movement of individual storms. There is minimal indication of cell training. Precipitable Water (PW) values are between 1.25 and 1.50 inches and are pooling ahead of this system.
Taking a look at PW for Birmingham, note that this PW range represents seasonal values in at least the 90th percentile. Thus, depending on other factors, heavy rainfall is indeed possible.
One limiting factor, and a significant one, is the steady eastward movement. The heaviest precipitation is caused by forcing directly along the cold front. The progressive frontal movement should limit the period of heaviest rainfall.
Following is a short-term precipitation model valid late this evening. Generally, rainfall amounts in the 0.50 – 1.50 inch range can be expected, with areas of heavier rain closer to 2 inches. Of course, isolated amounts could be even higher – but will be on a local, and not basin, scale.
Key runoff thresholds range from 2.5 inches on the low side to 3.5 inches on the high side over most of Alabama and Georgia.
What To Expect
- Strong storms are likely to produce enough rain in a short period of time to cause flash and urban flooding, and pooling of water in poorly-drained spots.
- There is the possibility of strong within-bank rises or isolated minor flooding along the Tombigbee River as well as smaller tributaries and drainages.
- For the most part, basin-scale rainfall amounts are not likely to bring river to flood stage (except smaller tributaries).
(For river forecasts, outlooks, and warnings – refer to official NWS information)
A welcome rain/snow event occurred over parts of the Midwest the past few days. Precipitation was especially welcome over parts of Nebraska, Kansas, and Iowa. Areas in yellow received over 2 inches of rainfall.
Early Hurricane Outlook
Dr. William Grey issued his first outlook for the hurricane season. He is calling an an active season. Here is his forecast.
Following is the ENSO Multivariate ENSO Index (MEI) (black plot) compared to six other similar years. You might remember a while back when the ENSO signal was dropping from a weak El Nino to neutral, it was falling much quicker than past similar years. What is interesting here is to see the wide spread of the six comparison years. For example, 1990-91 rose to 1.5 while 1966-67 fell to -0.5. In any event, the odds strongly favor neutral conditions for most of the remainder of 2013.