North Central Gulf Coast Historic Flash Flood Event – 29-30 April 2014

A historic rainfall event (see Fig. 1) developed ahead of a slow moving cold front on Tuesday evening, 29 April 2014 over portions of coastal Alabama and the western Florida Panhandle. The cold front was associated with a very powerful low pressure system in the Plains. The widespread flooding produced sinkholes (some very large and deep), cut roads in half and necessitated human water rescues (one confirmed fatality). Parts of I-10 were closed. The Fish River at Silver Hill (Baldwin County Alabama) peaked at a record high level of 23.18 feet (previous historical record was 22.78 feet on 20 July 1997).  Many folks throughout the area have compared this event to the extreme flooding impacts caused by Hurricane Danny (1997).

The rainfall totals below were contributed to by two predominant rounds of storms, the first occurred Monday night 28 April and into the early morning hours of Tuesday 29 April when significant flash flooding occurred over coastal Alabama and the western Florida Panhandle. Some 3-8” occurred in association with the first event ending 7 AM CDT Tuesday 29 April. The second and more significant event occurred during the evening hours of Tuesday 29 April over Mobile and Baldwin counties of Alabama and the western most three counties of the NW FL Panhandle into early morning hours Wednesday 30 April.  In the latter, some 10-15” fell in a very short time period (estimated 9 hours preliminarily) and caused disastrous flooding throughout southern Baldwin County of Alabama and Escambia, Santa Rosa and Okaloosa counties of the western Florida Panhandle.  Figures 2-4 show how the rain fell over time. CoCORaHS gauge reports are included in Tables 1-8 below.

Also of note, the official NWS reporting sites at Mobile Regional Airport (MOB) and Pensacola Regional Airport (PNS) received some record rainfall amounts for 29 April. MOB saw 11.24" during the calendar day.  This is their 3rd greatest calendar day total on record.  Data here goes back to 1871.  PNS recorded an estimated 15.55".  Data were lost due to power outage between 10-11 PM CDT, so amounts were estimated using Dual Pol radar precipitation estimates. This is their greatest calendar day total on record. PNS rainfall data goes back to 1879. Of interest in the PNS total is the 5.68" that fell in 1 hour between 02Z-03Z.  A quick peek of the NOAA HDSC Precipitation Frequency map shows this to be a 1 in 200 year to 1 in 500 year 1 hourly amount.  The 24 hour amount is between a 1 in 50 and 1 in 100 year event.  The Mobile 24 hour total is about a 1 in 25 year event.

Of significance, the two day estimated total for Pensacola of 20.47" lies between a 1 in 100 to 1 in 200 year event.

Finally and although not shown, it is worth mentioning that leading into the event, rainfall totals for the past two weeks and 30 days prior to the occurrence of this event that rainfall totals were 200-600% of normal according to 30 year PRISM Data.

Figure 1  - Radar estimated event rainfall totals (in.) between 848 PM CDT Mon., 28 April – 920 AM CDT Wed., 30 April. See scale on top.
Radar estimated event rainfall totals (in.) between 848 PM CDT Mon., 28 April – 920 AM CDT Wed., 30 April


How did the Rain Fall over Time?  Below is the radar-estimated depiction of how the historic rains fell over time.


Figure 2  - Radar estimated event rainfall (in.) totals between 9 AM CDT Mon., 28 April – 9 AM CDT Wed., 30 April. Scale on right.
Radar estimated event rainfall (in.) totals between 9 AM CDT Mon., 28 April – 9 AM CDT Wed., 30 April. Scale on right


Figure 3  - Radar estimated event rainfall (in.) totals between 9 AM CDT Mon., 28 April – 9 AM CDT Wed., 30 April. Scale on right.
Radar estimated event rainfall (in.) totals between 9 AM CDT Mon., 28 April – 9 AM CDT Wed., 30 April. Scale on right.


Figure 4  - Radar estimated event rainfall (in.) totals between 9 PM CDT Tue., 28 April – 9 AM CDT Wed., 30 April. Scale on right.
Radar estimated event rainfall (in.) totals between 9 PM CDT Tue., 28 April – 9 AM CDT Wed., 30 April. Scale on right

Two day CoCoRaHS Rainfall Reports (by State to include Coastal SW AL, NW FL and SE MS)– All reports ending times vary. Data from 28-30 April, 2014.


Table 1 – SW Alabama - Mobile County


Table 2 – SW Alabama - Baldwin County


Table 3 - Northwestern Florida Panhandle - Escambia County


Table 4 - Northwestern Florida Panhandle - Santa Rosa County


Table 5 - Northwestern Florida Panhandle - Okaloosa County

The following is courtesy of the 96th Weather Flight, Eglin AFB
 KVPS  Eglin AFB
 10.46    10.46
 KEGI  Duke Field
 9.83    9.83

 

 

 


Table 6 - Southeastern Mississippi -Wayne County


Table 7 - Southeastern Mississippi -Stone County


Table 8 - Southeastern Mississippi -George County

Disclaimer:   The NWS in Mobile reserves the right to update this page as more information becomes available.


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