2011 Arklamiss Warm Season Outlook

NWS Jackson

NWS Southern Region

Winter Outlook - Recap Precipitation:

South of US Highway 82: 50% chance of below normal, 30% chance of near normal, 20% chance of above normal Verification since December 1: Jackson 3”

below normal, Meridian 6” below normal, Tallulah-Vicksburg 5” below normal, Hattiesburg 6” below normal

US Highway 82 and North: 30% chance of below normal, 40% chance of near normal, 30% chance of above normal Verification since December 1: Greenwood 5.5”

below normal, Greenville 8” below normal

NWS Southern Region

Temperatures Highly variable, but expected to average out above

normal for temperatures Verification: Bust! Temperatures have averaged

below normal everywhere Severe weather:

50% chance of above normal severe weather, 30% chance of near normal, 20% chance of below normal Verification: Above normal tornadoes, primarily

November 29 and New Year’s events Winter Weather

Below normal likelihood of a significant snow event, Near to somewhat above normal risk for a significant icing event Verification: Icing correct, snowfall wrong

NWS Southern Region

Why So Cold?

Negative NAO Persistent East Coast Trough

NWS Southern Region

ENSO Status

Currently in a moderate to strong La Nina episode

As is typical, the La Nina should weaken through the spring

Expected to become neutral this summer

El Nino

La Nina

CurrentForecast

NWS Southern Region

Spring Outlook - Methodology Look for years in which the La Nina phase was similar

to this year 1976, 1989, 1999, 2000 were the best matches

Look at other key atmospheric and oceanic indices to see how they match

Use typical La Nina impacts for the region, CPC forecasts, and impacts during the analog years and extension of recent trends, to give some probabilities as to what the spring may bring

NWS Southern Region

La Nina Impact El Nino/La Nina is the prime

driver of the global atmospheric pattern, although there are other important processes at work

The La Nina impact is clearest during the winter season (and the tropics in the summer); not as defined during the rest of the year

Overall, trend toward warmer and drier than normal, particularly in the southern sections of the Arklamiss

Typical Spring La Nina Rainfall Patterns

NWS Southern Region

CPC Spring Outlooks

Temperatures Precipitation

NWS Southern Region

Spring Flooding – Arklamiss Rivers

Rainfall has been below normal nearly everywhere last 90 days

Combined with forecast near to below normal spring rainfall – below normal spring flood threat

% of Normal Precipitation Last 90 Days

NWS Southern Region

Spring Flooding – Miss River• 2-4” of liquid water in the upper MS Valley• Most of the snow in the OH and mid-MS valleys has melted in the last 5 days

• This reduces the risk to the lower MS valley

• Above normal rain forecast in Ohio Valley, but below normal in Arkansas/Red• Overall, expect near normal flood threat for the lower Mississippi River

Snow Water Equivalent in Inches

NWS Southern Region

Spring Flooding – Miss River

NWS Southern Region

Severe Weather Average number of tornadoes (Feb through May):

All years: 28 total, 11 strong Analog years: 36 total, 12 strong

Three of the four years were above normal for tornadoes and strong tornadoes Some notable severe weather events occurred during

the analog years March 26, 1976 “Simpson County” March 29-30, 1976 April 14, 1999 Moss Tornado Event

NWS Southern Region

Decadal Tornado Trends

41 strong tornadoes since 2006 – almost as many as the entire previous

decade

NWS Southern Region

Sea Surface Temperatures

Cooler than

Normal

NWS Southern Region

Spring Outlook

Temperatures: 50% chance of above normal, 30% chance of near normal, 20% chance of below normal

Precipitation: 50% chance of below normal, 30% chance of near normal, 20% chance of above normal

Slightly higher chances of near/above normal rainfall in northern parts of area

Severe Weather: Equal chances of near/above/below normal (no clear signal)

Flooding: Below normal on area rivers; near normal on the lower Mississippi

NWS Southern Region

Peek at Hurricane Season

Warmer than

Normal

NWS Southern Region

Peek at Hurricane Season

Warmer than normal Atlantic sea surface temperatures Favors above normal tropical season

Neutral or weak La Nina conditions expected this summer

Favors above normal tropical season Active period of “multi-decadal” signal favors more

active than normal conditions Gray-Klotzbach December forecast: 17 named storms,

9 hurricanes and 5 major hurricanes (normal is 11, 6, 2)

NOAA forecast will be issued in May