Jeff Masters on TS Debby & Continuing Record Heat

Debby stalls, drenches Florida; 114° in Colorado ties state heat record
Posted by: Dr. Jeff Masters, 1:09 PM GMT on June 25, 2012 +32

Tropical storm warnings continue to fly from Alabama eastward to Suwannee, Florida, as Tropical Storm Debby sits motionless over the Gulf of Mexico. On Sunday, Debby spawned a multitude of severe thunderstorms over much of Florida, which brought torrential rains, damaging winds, and numerous tornadoes. NOAA’s Storm Prediction Center logged 20 preliminary tornado reports on Sunday, and a tornado in Venus, Florida killed one person. Venus is in Central Florida, between Port St. Lucie and Sarasota. Another person is missing in Alabama, swept away by rough surf. The heaviest rains of Debby affected the Tampa Bay region, where over ten inches were reported at several locations. The Tampa Bay airport picked up 7.11 inches on Sunday. It’s a good thing this isn’t the week of the Republican National Convention, which is scheduled for late August in Tampa! Minor to moderate flooding is occurring at three rivers near Tampa, and flooding has been limited by the fact the region is under moderate to severe drought.

Figure 1. Radar-estimated rainfall from Tropical Storm Debby has totaled over 6 inches (orange colors) along a swath from Tampa to Ocala.

Winds from Debby have fallen considerably since Sunday, thanks to a slug of dry air that wrapped into Debby’s core, disrupting the storm. Our Wundermap for the surrounding ocean areas shows that winds at almost all buoys and coastal stations along the Gulf Coast were below 30 mph at 8am EDT. The exception was a Personal Weather Station at Bald Point, near Apalachiacola, Florida, which reported sustained winds of 32 mph. An Air Force hurricane hunter aircraft flying through Debby has measured top surface winds of 43 mph as of 9 am EDT. Visible satellite loops show Debby has virtually no heavy thunderstorms near its center of circulation, which will severely limit its potential for intensification today. The heavy thunderstorms of Debby are mostly on the east and north sides. Upper-level winds out of the west creating a moderate 10 – 20 knots of wind shear that continues to drive dry air into Debby’s core. This dry air can be seen on Water vapor satellite loops. Ocean temperatures are about 27.5°C (81°F) in the Northern Gulf of Mexico, which is about 1°F above average, but these waters do not extend to great depth, which will limit how strong Debby can get.

Figure 2. True-color visible Aqua satellite image of Debby taken at 3 pm EDT Sunday June 24, 2012. At the time, Debby had top winds of 60 mph. Image credit: NASA.

Forecast for Debby
Debby’s slow motion will make rainfall the primary threat from the storm, though tornadoes will continue to be a threat over the next few days. NOAA’s Storm Prediction Center has placed most of Florida in its “Slight Risk” area for severe weather today. The slow motion of Debby will inhibit intensification of the storm by stirring up cooler waters from the depths to the surface. Debby’s close proximity to land places a portion of its circulation over land, which will also tend to slow down intensification. Wind shear is expected to remain in the moderate range through Wednesday. I expect Debby will begin to build heavy thunderstorms near its core today and Tuesday, with the winds increasing again to 60 mph by Wednesday morning. The latest SHIPS model forecast gives Debby just a 4% chance of undergoing rapid intensification–a 30 mph increase of winds in 24 hours. The 8 am EDT NHC wind probability forecast is giving Debby a 19% chance of becoming a hurricane by early Wednesday morning. Steering currents for Debby are very weak, a the storm should hang out in its current location for several more days. The models continue to have a large spread in where they thing Debby might eventual make landfall, and the official NHC forecast may have large errors for its positions at the 3 – 5 day range.

Colorado’s 114°: hottest temperature in state history
The remarkable heat wave that affected Colorado on Saturday and Sunday has tied the all-time heat record for the state. According to wunderground’s weather historian Christopher C. Burt, Saturday’s 114° reading in Las Animas tied for the hottest temperature ever measured in the state of Colorado. Two other 114° readings have occurred in Colorado history: in Las Animas on July 1, 1933, and in Sedgwick on July 11, 1954.

Colorado Springs tied its all-time record for warmest temperature ever measured on both Saturday and Sunday, with readings of 100°. The city has hit 100° four other times, most recently on July 24, 2003. The record heat in Colorado Springs exacerbated a wildfire that grew to more than 3 square miles on Sunday, driving 11,000 residents (2% of the city’s population) out of their homes.

In Fort Collins, the mercury hit 102° on Sunday, just 1° below the city’s all-time hottest temperature of 103° set on Jul 21, 2005. The heat did no favors for firefighters struggling to the contain the massive 81,000 acre High Park fire fifteen miles northwest of Fort Collins. The fire is the second largest and most destructive wildfire in Colorado’s history, and is 45% contained.

La Junta, CO hit 110° on Sunday, tying its all-time hottest temperature record, set on June 28, 1990.

The heat wave extended into neighboring Kansas, where Hill City hit 114°, tying its all-time warmest June temperature. Tribune, Kansas hit 109°, tying its all-time hottest temperature. Goodland, Kansas hit 109°, its hottest June temperature on record.

Two more days of exceptional heat are predicted for Colorado and Kansas, with the forecast for Denver calling for a high of 101 – 104° on Monday. The city hit 102° on Sunday, just 3° below the hottest temperature ever recorded in Denver, the 105° readings on July 20, 2005 and August 8, 1878.

Jeff Masters