Yet Another Record High!

Once again, record heat was experienced across the Tennessee Valley. The recorded high temperature at Lovell Field was 103 degrees, which surpassed the old record of 100 set in 1983. We are still on pace for the hottest August on record with an average temperature of 85.9 degrees. The current record belongs to August 1993 with an average of 82.5, so we are currently well above the number. August 2007 could also go down as the hottest month ever recorded in Chattanooga.

Now for some "cool" thoughts to ease the heat:

- Today's Record Low: 55 (1956)....It is possible to actually have cooler weather this time of year!

- Autumn is only 31 days away

- The average date of the first frost is October 21st (just 2 months away)

- Yesterday's high temperature at Mt. LeConte, TN (elevation 6600 ft) was only 72.

Felix Forming?

August 15-October 15 is typically the busiest 2 months of the hurricane season and this year has started heating up right on time. Dean reached the Top 10 list of strongest recorded hurricanes before plowing into the Yucatan. Cancun was spared the worst with Chetumal to the south taking the brunt of the storm. Dean should move back over water in the southern Gulf (Bay of Campeche) before making a second landfall. The second landfall in Mexico will be far less severe than what occurred on the Yucatan. As Dean begins moving away, another system is being watched well east of the Bahamas. A tropical wave interacting with an upper low is tightly clustering t-storms and upper level conditions are beginning to improve for some development over the next couple of days. The NAM, North American Model puts this system near the Bahamas over the weekend with a continued westerly movement. The tropical model suite (see image above) also favors a westerly path with some slow development. So, "Felix" could be on the horizon.

Dean Makes Landfall

HURRICANE DEAN ADVISORY NUMBER 33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007
400 AM CDT TUE AUG 21 2007

...CATEGORY FIVE HURRICANE DEAN MAKES LANDFALL ON THE EAST COAST OF
THE YUCATAN PENINSULA OF MEXICO...

AT 400 AM CDT...0900 UTC...THE GOVERNMENT OF MEXICO HAS REPLACED THE
TROPICAL STORM WARNING AND HURRICANE WATCH WITH A HURRICANE WARNING
FROM WEST OF CHILITEPEC TO VERACRUZ MEXICO.

REPORTS FROM AN AIR FORCE HURRICANE HUNTER PLANE INDICATE THAT THE
EYE OF DEAN MADE LANDFALL ON THE EAST COAST OF THE YUCATAN
PENINSULA NEAR COSTA MAYA OR MAJAHUAL AROUND 330 AM CDT. THIS
LOCATION IS ABOUT 40 MILES...65 KM...EAST-NORTHEAST OF CHETUMAL
MEXICO

MAXIMUM SUSTAINED WINDS ARE NEAR 165 MPH...270 KM/HR...WITH HIGHER
GUSTS. DEAN IS A CATEGORY FIVE HURRICANE ON THE SAFFIR-SIMPSON
SCALE. ALTHOUGH SOME WEAKENING IS FORECAST AS DEAN CROSSES THE
YUCATAN PENINSULA...DEAN IS EXPECTED TO MAINTAIN HURRICANE STRENGTH
THROUGHOUT THE NEXT 24 HOURS.

Dean Reaches Category 5 Strength

HURRICANE DEAN ADVISORY NUMBER 32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007
1100 PM EDT MON AUG 20 2007

...EYE OF POTENTIALLY CATASTROPHIC HURRICANE DEAN JUST A FEW HOURS
FROM LANDFALL ALONG THE EAST COAST OF THE YUCATAN PENINSULA..
MAXIMUM SUSTAINED WINDS ARE NEAR 160 MPH...260 KM/HR...WITH HIGHER
GUSTS. DEAN IS A POTENTIALLY CATASTROPHIC CATEGORY FIVE HURRICANE
ON THE SAFFIR-SIMPSON HURRICANE SCALE. LITTLE CHANGE IN STRENGTH
IS EXPECTED PRIOR TO LANDFALL ON THE EAST COAST OF THE YUCATAN
PENINSULA. ALTHOUGH SOME WEAKENING IS FORECAST AS DEAN CROSSES THE
YUCATAN PENINSULA...DEAN IS EXPECTED TO MAINTAIN HURRICANE STRENGTH
THROUGHOUT THE NEXT 24 HOURS.

Former Chattanoogan riding out Dean in Cancun

Former Chattanoogan Gene Hilton now lives in Cancun, Mexico. I spoke with him Monday evening and he gave this account of the conditions as Hurricane Dean moves in. "The outer bands have moved in and the conditions have worsened, we are hunkered down in our condo for the storm." Hilton said that he and his wife have taken the proper steps to protecting their condo with storm shutters in place. He was also amazed that people were still on the streets as the outer bands moved in at 9pm local time in Cancun.

Dean Heads For Mexico...Record August Heat Locally

After a weekend visit to Jamaica, Dean should continue a westward motion passing south of the Cayaman Islands. This will also include a pass over the warmest waters of the Caribbean Sea and allow for more intensification possibly to Category 5 strength. The Mexican coast of the Yucatan Peninsula is the next land mass to be affected. Popular tourist sites like Cancun and Cozumel will be affected by the outer bands of Dean, while the center will pass south of there. Tulum, a city on the coast by south of Cancun, could be near the area hardest hit. Tulum took a devastating blow from Hurricane Wilma in 2005 and Dean could be another setback. Once Dean passes over the Yucatan, there should be significant weakening and even a pass back into the warm waters of the Bay of Campeche will still not allow Dean to return to its prior strength before a second landfall in Mexico.

Locally, the heat continues and we are well on our way to setting the record for the all time hottest August. Here is where we stand so far, through Sunday the average temperature for the month was 85.8 degrees. The current record holding August was in 1993 with an average temperature of 82.5 degrees. Do the math and you realize that this August could shatter the old record by leaps and bounds! As I have mentioned in past posts, the reason for this extreme heat not only lies with upper atmospheric conditions, but the extreme drought. The lack of soil moisture and subsequent moisture in the air allows for higher surface heating temperatures. It's kind of like baking some cookies with dough that is not moist enough....they will burn in a short period of time. Our humidity levels should only slowly move up over the next few days, and a few isolated showers are possible. Air temperature readings should remain in the upper 90s with a visit to 100 not impossible during the work week. Some relief may be in sight for next week. An upper level trough has been indicated by several long range computer model runs. While the timing is differnt with each model run, the models are consistent in indicating that suh a trough should develop somewhere in the 6-10 day time frame. This could take a huge chunk out of the heat and even swing some showers/thunderstorms our way with the passage of a cold front. The latest 6-10 day outlook from the Climate Prediction Center is starting to show signs of the changes ahead. Again, we have another very hot week ahead, but some signs of change are slowly emerging for the following week.

Jamaica Topping "Dean's" List

Major Hurricane Dean could be on a collision course with Jamaica by Sunday. Dean is located in an environment which should sustain the current strength along with intensification. It is possible for Dean to be a strong Category 5 hurricane when it arrives on the Jamaican coast. After Jamaica, the Cayman Islands and Cancun/Cozumel will be on the radar for a visit from Dean. The longer range outlook for the United States would favor a landfall from the south Texas coast southward to along the Mexican coast. As far as Dean's strength at that point will depend on its rendezvous with the Yucatan Peninsula. A longer time over land should allow the storm to weaken from 4 or 5 strength. Once this occurs to a storm it will make it much harder for the storm to regain its once powerful strength. A shorter time spent over the landmass of the Yucatan will mean that Dean could sustain its strength.
Our region should not have any effects at all from Dean. Most, if not all of the moisture should still well south of our region, and the hot/dry pattern will continue.

Another Day, Another Record......A Look Back At Forecast

Today's official high temperature at Lovell Field was 104 degrees which surpassed the old record of 101 set back in 1954. It was the second straight day of record breaking temperatures. The last time Chattanooga recorded a high of 104 was on July 29, 1993. Today was not far from the all time record of 106 set in late July of 1952. The Exceptional Drought that we are experiencing has everything to do with the fact that temperatures are extremely high. A lack of soil moisture results in lower air humidity values and hotter temperatures. It's a pattern that is often seen in the southwestern US and not here in the southeastern US. If you have been a regular reader of my blog you might recall my Summer outlook from May 10th which told of the possibility that the drought could lead to extreme heat. Here is an excerpt from that column:

(From May 10th Blog Entry): The Drought Monitor closely studies the entire country and determines the severity of dry spells. These drought conditions leading into the summer, could cause a warmer than normal summer.

A normal rain pattern would have led to an ample ground supply of water. Moisture in the top layer of the soil can serve to keep temperatures in check through evaporation. Granted, the added moisture in the air provides a muggy feeling, the evaporation and evapotranspiration process will keep air temperatures near seasonal levels. A parched, dry soil layer will absorb and retain the heat, therefore warming the air and leading to above normal temperatures. Again, on the flip side, it is not as humid, but very hot. The 2 week temperature trend keeps us in the above normal category. So, unless a wetter than normal pattern begins to take hold in June, we could be in for a hot summer.

Tropical Update: Dean is now a hurricane and should become a major one as it races through the Caribbean Sea. It "could" affect Jamaica and the Cayman Islands over the weekend and potentially Cancun by Monday. The forecast cone is close to the consensus of computer model guidance which indicates a west-northwest movement. At the current time, the western Gulf looks to be the region of highest risk from Dean next week. If this occurs, the Tennessee Valley should have no impacts at all and the heat will continue.