Weather In Review And Forecast For April 12, 2015

Severe weather outbreak struck on April 9, 2015. Strong tornadoes reported throughout Midwest to South. Monster tornadoes flattened Fairdale, Illinois, which is west of Chicago. Here is a severe weather map of the outbreak.

20150413_SevereWeatherMap

Most areas reported strong winds, while there were 20 tornadoes reported, mostly in Illinois. Hail also fell throughout the Central US. Two people lost their life in the severe weather outbreak in Northern Illinois. What would allow severe weather to happen last week?

20150413_500mb_GeopotentialHeightAnomaly_NH

Notice, there is upper level ridging over the eastern half of the US, while there is upper level troughing over the Western US. This type of setup is more favorable for severe weather including tornadoes. The ridging over the Eastern US brings in warm Gulf of Mexico air, while troughing brings in cool air from Canada, which is less favorable for tornadoes and severe weather. This article explains it well. That type of setup with troughing over Western US and ridging over Eastern US played a role in active tornado seasons of 1998, 2004, 2008, and 2011.

Tornadoes usually occur when warm air from the Gulf of Mexico clashes with cold air from Canada. It happens as we are transitioning from Winter to Summer. It happens vice versa with Summer to Winter. Hence, why Spring and Fall are very active for tornadoes and severe weather.

20150413_SurfaceTemperatureAnomaly_NH

Many areas of the US experience warmer than normal temperatures, which contributed to the severe weather outbreak last week. Could we see a repeat of last week this week? Let’s look at rainfall forecast totals.

20150413_GFS_AccumulatedPrecipitationTotal_USA_168Hour_1800Z

20150413_GEM_AccumulatedPrecipitationTotal_USA_168Hour_1800Z

Both Canadian and GFS agree that it will be a wet next 7 days. The difference is in amount. Canadian is more generous with rainfall total, while GFS has less rainfall total. Canadian goes as high as 10 inches, while GFS goes as high as 6 inches of rain. This week will be a wet one for sure.

Since, I used upper air analogs and predicted potential tornado outbreaks, I shall use them again. I like using analogs. Let’s start with 6 to 10 day analog forecast.

20150413_6To10Day_AnalogForecast

4/23/1995-Severe reported throughout Central and North Texas on 4/26. Severe weather outbreak on 5/7 throughout West, Central, and North Texas. New Orleans struck by heavy rain on 5/8-10 from same system that caused severe weather in Texas. Many areas saw 10 to 20 inches of rain, including 34 inches of rain in Lacombe, Louisiana. It is the worst flooding for New Orleans area between Betsy and Katrina.
4/5/1973-Houston records its latest freeze on 4/10 of 31°F.
4/27/2004-Tornado hits Qishi in Guangdong Province of China claiming 2 lives on 5/9.
4/7/1957-Texas has its wettest April on record at a time when it suffered from a severe drought of the 1950s.
4/11/1959-Heavy rain occurs in Houston area between 4/8-11. Rainfall totals are Houston WB: 6.22″; Hobby: 7.01″; Galveston: 1.77″. Houston sees its second wettest 4/8 and 4/9 and all time wettest 4/11 on record. It leads to flooding in Houston area.
4/4/1977-Birmingham, Alabama area is hit by a powerful tornado on 4/4. It is part of a tornado outbreak that hits on 4/4-5. 22 of the 25 fatalities are in the city of Tarrant in Jefferson County.
4/15/1983-Tornado outbreak on 5/1-2. 63 tornadoes are reported in 11 states claiming 7 lives.

Here is the 8 to 14 day analog forecast.

20150413_8To14Day_AnalogForecast

4/25/1995-Severe reported throughout Central and North Texas on 4/26. Severe weather outbreak on 5/7 throughout West, Central, and North Texas. New Orleans struck by heavy rain on 5/8-10 from same system that caused severe weather in Texas. Many areas saw 10 to 20 inches of rain, including 34 inches of rain in Lacombe, Louisiana. It is the worst flooding for New Orleans area between Betsy and Katrina.
4/20/1983-Tornado outbreak on 5/1-2. 63 tornadoes are reported in 11 states claiming 7 lives.
4/25/2005-A unusual late April to early May cold spell hits east of the Rocky Mountains.
4/7/2009-Tornado outbreak on 4/9-11 hits the Southeastern US. 85 tornadoes are reported that claim 5 lives and an addition 4 lives from fires in Texas. Heavy rain plagues Southeast Texas throughout the month of April.
5/8/1980-Period of rains for 7 days in Houston area from 5/12-19.

The 6 to 10 day and 8 to 14 day analog forecasts are mostly similar dates with some having different dates. Looking at the analog dates that stood out, they mostly had severe weather and tornado outbreaks. Some had heavy rain and flooding. One had a unusual late April to May cold spell. This suggests that we could see more severe weather outbreaks this week to next. It also raises the possibility of heavy rain, especially along the Gulf Coast including Texas.

I think this week could see heavy rain and flooding, especially in Texas, Louisiana, Alabama, and Georgia. We are in a setup for rain and thunderstorms.

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