Thermal effect of water

[Walt]

December of 2010 was the worst month of cold I've ever experienced in my 13 winters living in Highlands County, Florida. You can't get any farther inland between the Atlantic and Gulf of Mexico. As such, there is no thermal influence from both bodies of water. However, there is a thermal lake effect influence, but it doesn't carry far.

I have three friends who live in a lake front community. All are master gardeners (as myself), hence they are concerned about and record low temperatures. Two of my friends live right on the lake (3,504 acres in area) and one friend lives about 500 feet of the east shore of the lake.

On my coldest night last December I recorded a low of 20.7 in my open yard. My friend who lives 500 feet from the lake recorded 31.9 degrees (his lowest for the entire month). One of my friends that lives right on the lake recorded 38 degrees in his back yard nearest the lake (the other friend said he didn' have a thermometer out but that there was never a frost or freeze in his yard).

I was just over to all three friend's homes yesterday and their yards and tropicals looked great -- while mine are burnt to a crisp!

Last December 2nd I snapped the below screen save. I took the photo at 6 a.m. EST (as you can see in the lower left hand side of the photo).

Note the temperature color gradient (dark green warm to light blue colder) showing the thermal effect of the water. Note the thermal carry-out effect from the southeast side of Lake Okeechobee.

Note southern Pinellas County (St. Petersburg, Florida). St. Pete in places ran consistantly warmer than southeast Florida. I checked this temperature map every morning and Albert Whitted airport area is consistantly warmer than any other spot in central Florida and oft times warmer than Ft. Lauderdale and Miami.

[Ed in Houston]

Yes Walt, I see this alot in the Houston/Galveston Bay area. As one heads SE from the Houston heat island, one goes toward Galveston Bay and the warming effect from the bay begins to take effect and can be quite pronounced. In my area it usually adds about 3 degrees compared to other directions from the center of the city heat island. When it is windy, as during the recent advective freeze, the effect is less than on calm nights. Also during long cold spells that we sometime have here, the bay seems to get drained of its heat and the effect can be less. During freeze events, I always hope for high pressure to move just enough east to produce an easterly component to the wind. This allows more heat from the bay to blow into SE Houston.

Ed in SE Houston

[sonoranfans]

Yup,

I commute to work in pinellas and live in manatee county 4-5 miles SE of tampa bay. You can see how the burn of various species of palms is reduced near the water. From royals and foxtails to dypsis lutecens and adonidias, you can see "burn patterns" in the common zone 10 palms in the area. The airport is a warm part of pinellas, the warmest parts are SW pinellas as seen in the map, the adonidia burn in particular tells the story. I also noted that when my house hit the low of 28.5 F, holmes beach was 41F, and miami was 38F. I think this pattern of warmth holds true when the weather is coming from the west or especially the cold blasts from the northwest. When the weather is coming from the northwest, pinellas sees air that has come over water in the gulf, and miami sees the air from central florida(colder air). Because miami has the warm ocean(warmer than the gulf in mid to late winter), it will warm up quickly when the breeze shifts coming from the east off the ocean. For the west coast it partly depends on the gulf water temperature. Last year the gulf was colder and it hit 26F in st pete which was closer to the temps down in bradenton area. When we get a few days of weather from the south west, warm water is pushed in from the southwest and the gulf temps shoot up. The pinellas peninsula had the advantage that air is warmed coming from the west and also to a lesser extent from the east(tampa bay).

I find the 3500 acre lake results very interesting Walt, its a huge lake and apparently having a big impact in central florida.

Edited February 8, 2011 by sonoranfans

[happ]

Water ala the Pacific ocean has tremendous influence on temperatures along the West Coast. For a variety of reasons that includes the prevailing westerlies, high mountains and the ocean, California is often spared the kind of weather that is more common in the U.S. South. For example the idea of an ice storm is so alien to be unheard of. Occasionally "back door" fronts transport arctic air masses that retrograde westward into the state but overwhelmingly the conditions are dry and the skies clear. Cold storms migrate south out of the Gulf of Alaska but are greatly modified by passing over the ocean. Conversely during summer that same ocean cools the temperature to such an extend that coastal cities can be 20+ degrees cooler than areas merely 10 miles inland.

[spockvr6]

Conversely during summer that same ocean cools the temperature to such an extend that coastal cities can be 20+ degrees cooler than areas merely 10 miles inland.

Happ-

I remember driving some years ago from I think Imperial or El Centro (man did I have some of the best burritos Ive ever had out there) to San Diego. In any case, I had a rental car which was a convertible and it was mid July. I had the top down until I got into San Diego as I went from being roasted to cold in a very short period. I distinctly recall the car thermometer starting in the lower 110's with brilliant sunshine, and ending in the lower 60's and fog when I got into San Diego!

[Walt]

Yes Walt, I see this alot in the Houston/Galveston Bay area. As one heads SE from the Houston heat island, one goes toward Galveston Bay and the warming effect from the bay begins to take effect and can be quite pronounced. In my area it usually adds about 3 degrees compared to other directions from the center of the city heat island. When it is windy, as during the recent advective freeze, the effect is less than on calm nights. Also during long cold spells that we sometime have here, the bay seems to get drained of its heat and the effect can be less. During freeze events, I always hope for high pressure to move just enough east to produce an easterly component to the wind. This allows more heat from the bay to blow into SE Houston.

Ed in SE Houston

Ed: Same goes for the lakes here. If it's a strong advective night the air becomes more homogeneous to where those living on the lake recieve little benefit. I've been comparing low temperatures with my lake side friends for many years now. However, 95 percent of palm/tropical damaging cold weather events are radiational in nature. What advective events we have are normally not cold damaging (at least in the 13 winters I've lived here). I only recall one advective event when my low was 29.5 degrees, and that was in late January of 2003.

[Walt]

Yup,

I commute to work in pinellas and live in manatee county 4-5 miles SE of tampa bay. You can see how the burn of various species of palms is reduced near the water. From royals and foxtails to dypsis lutecens and adonidias, you can see "burn patterns" in the common zone 10 palms in the area. The airport is a warm part of pinellas, the warmest parts are SW pinellas as seen in the map, the adonidia burn in particular tells the story. I also noted that when my house hit the low of 28.5 F, holmes beach was 41F, and miami was 38F. I think this pattern of warmth holds true when the weather is coming from the west or especially the cold blasts from the northwest. When the weather is coming from the northwest, pinellas sees air that has come over water in the gulf, and miami sees the air from central florida(colder air). Because miami has the warm ocean(warmer than the gulf in mid to late winter), it will warm up quickly when the breeze shifts coming from the east off the ocean. For the west coast it partly depends on the gulf water temperature. Last year the gulf was colder and it hit 26F in st pete which was closer to the temps down in bradenton area. When we get a few days of weather from the south west, warm water is pushed in from the southwest and the gulf temps shoot up. The pinellas peninsula had the advantage that air is warmed coming from the west and also to a lesser extent from the east(tampa bay).

I find the 3500 acre lake results very interesting Walt, its a huge lake and apparently having a big impact in central florida.

Tom,

On a typical winter those living in immediate proximity of a large lake benefit greater as opposed to areas away from it, like my location. I've consistantly recorded 10-14 degrees colder than my friends on the lake on the coldest radiational cooling nights (we are about three miles apart as the crow flies).

However, last December and also January of 2010 were exceptions as the cold weather was so prolonged that the lake waters gave up a good amount of their heat. In January of 2010 we had eleven straight nights where temperatures dropped below 40 degrees and five of those nights below 30 degrees. And everyone of those nights were radiational events. As such, the lake waters cooled down that by the end of the 11 day periond, on the coldest night, many tender palms were cold damaged (stuff like adonidia and cocos nucifera). These palms never fully recovered over the past summer, but it appears they suffered no signifigant further damage this past December, so maybe by the end of this summer they will be mostly recovered.

[Walt]

Water ala the Pacific ocean has tremendous influence on temperatures along the West Coast. For a variety of reasons that includes the prevailing westerlies, high mountains and the ocean, California is often spared the kind of weather that is more common in the U.S. South. For example the idea of an ice storm is so alien to be unheard of. Occasionally "back door" fronts transport arctic air masses that retrograde westward into the state but overwhelmingly the conditions are dry and the skies clear. Cold storms migrate south out of the Gulf of Alaska but are greatly modified by passing over the ocean. Conversely during summer that same ocean cools the temperature to such an extend that coastal cities can be 20+ degrees cooler than areas merely 10 miles inland.

Happ: I'm aware of the Pacific influence, mountain ranges, etc. on southern Cal's climate. I have a Sunset book here that goes into detail on it.

Actually, here in mostly flat Florida, considering that 95 percent of our coldest weather is advective in nature, elevation is also a big factor in providing higher nighttime temperatures. In fact, in many cases it's more beneficial that bodies of water that's had their heat depleted from them over many straight nights of cold.

I live along the Lake Wales Ridge which runs down the spine of central Florida for about 100 miles or so. The ridge is hilly and the elevations vary from maybe 350 feet (at its highest point) to mostly around 150 feet average (at least in my area).

The first really severe radiatinal freeze I experienced here was January 5, 2001. My low was 22 degrees and my garden was wiped out, as was my subdivision. A few days later I drove into town (Lake Placid, Fl.) The town is up on the ridge at about 150 feet above sea level, whereas I'm down off the ridge. As I started driving up the long hill (about a mile) I began to notice less and less foliage damage, and by the time I got up into town there was no damage at all! The town was basically in a temperature inversion air layer and I estimate was about 10 degrees warmer than at my place, because papaya leaves, banana leaves, etc., weren't defoliated.

Here at my place I have pothos vines growing up the trunks of pine trees. On most radiational cooling nights that drop below freezing, my pothos vines willl get defoliated, but higher up on the pine tree trunks the damage stops. You can clearly see the 30 degree level (about the temperature the vines finally get defoliated).

The graphic below illustrates air stratification. I took this capture from the Florida Automated Weather Network's Homestead site this past December 8th at 9:30 p.m. Note the temperature difference between 60 cm (above ground) and 10 meters, a 10 degree difference!

[Ed in Houston]

Walt, the layering of warm and cold air during a radiational freeze is quite pronounced in central Texas also. The cold air flows down from the higher elevation hilly areas and down into the valleys. The image below covers east and central Texas from Houston in the east to San Antonio and Austin in the west. It is easy to see that the air has stratified with elevation and the valley areas are much colder than the ridges.

The Balcones escarpment runs from northern San Antonio and just west of the central Austin area. This area and to the west is known as the Texas Hill Country. The temperature stratification along the balcones escarpment is quite pronounced. One can see that in Austin the temp is 34 on the higher elevation station and 21 at the lower elevation station just to the east where the cold air drains.

When driving through the Austin area, one can see Sabal Mexicana that are naturalized in the area. Some would say that the palm is returing to this area as there are several reports from early Texas exploration that document tall palms in central Texas. It is easy to imagine how these palms would be at home in the wet creek beds in the warmer elevated areas.

Ed in SE Houston

[Walt]

Walt, the layering of warm and cold air during a radiational freeze is quite pronounced in central Texas also. The cold air flows down from the higher elevation hilly areas and down into the valleys. The image below covers east and central Texas from Houston in the east to San Antonio and Austin in the west. It is easy to see that the air has stratified with elevation and the valley areas are much colder than the ridges.

The Balcones escarpment runs from northern San Antonio and just west of the central Austin area. This area and to the west is known as the Texas Hill Country. The temperature stratification along the balcones escarpment is quite pronounced. One can see that in Austin the temp is 34 on the higher elevation station and 21 at the lower elevation station just to the east where the cold air drains.

When driving through the Austin area, one can see Sabal Mexicana that are naturalized in the area. Some would say that the palm is returing to this area as there are several reports from early Texas exploration that document tall palms in central Texas. It is easy to imagine how these palms would be at home in the wet creek beds in the warmer elevated areas.

Ed in SE Houston

Ed: Another climatic factor here in inland Florida is the heat island effect of larger metropolitan areas. The graphic below shows the warmer Orlando, Leesburg, and Lakeland areas (darker green) running warmer than the outlying areas that have less heat absorbing density of concrete buildings, roads, etc., plus less heat generating sources such as homes, cars, etc.

The graphic below was taken earlier in the night. As the night wore on the heat island effect became less as the stored heat was released. Still, overall, the metro areas ultimately ran warmer than the outlying areas by day break. Typically, during the core winter months, my lows generally bottom out around 7:30 a.m.

[spockvr6]

Note southern Pinellas County (St. Petersburg, Florida). St. Pete in places ran consistantly warmer than southeast Florida. I checked this temperature map every morning and Albert Whitted airport area is consistantly warmer than any other spot in central Florida

Big time differential this AM between locations near water and those inland just a little bit. I logged 39F this AM, Fred Howard Park in coastal Tarpon Springs was 44F, while Albert Whitted in downtown St. Pete bottomed at only 51F.

[spockvr6]

Same thing again this AM......the water these past few nights has made a huge huge difference.

My house in Tarpon Springs 38F (about a mile and a half from the Gulf), coastal Tarpon Springs 45F, and downtown St Pete by the Bay 51F.

[sonoranfans]

This was interesting today Holmes beach recorded 43F, my house about 4 mi SE of tampa bay, 10 miles east of holmes beach was 41F. Our temps were unusually close to the holmes beach temps probably because the prevailing winds were from the NE for most of the night. If the winds were coming off the gulf, holmes beach would have been about +7F. Currently we(coachhouse station palmetto) are 68F and holmes beach is 63F.

Edited February 14, 2011 by sonoranfans

[gsytch]

Yes, Larry - the proximity to water has made the largest difference this winter. While I suffered through freezes, it was the frost that was heavy on one night that did my damage. Since the last freeze event Jan 6-9 timeframe, I've only seen a light frost/close freeze a few nights despite the chill. However, go up to my school in Hudson (15 mi N and E inland) and Queens are completely burnt, even Washingtons are showing damage, and Oleanders are cooked. Go down toward St Pete, and the damage is superficial. However, as is typical in Feb I cannot get above 68f due to afternoon sea breezes. Today Wesley Chapel hit 72f, I was 67f. Yesterday I hit 63f while Orlando hit 72f. btw Mesa,AZ (Phoenix suburb) hit 21f so I think that Phoenix temp was a lot lower - just another airport runway temp like Tampa. The dark runway, open area that creates a breeze, and near a heat effect keeps temps up a few degrees.

Now - spring come on and get here. 70's from now on thru Monday!

[Walt]

I'm still trying to figure out what physical dynamics are at play with regard to St. Pete vs. West Tampa/MacDill AFB. It seem MacDill runs notably colder most nights than southern Pinellas/St.Pete area, even though MacDill is at the south end of the West Tampa peninsula, surrounded on three sides by water (Tampa Bay).

On one particular night this past December Albert Whitted Airport was actually 10 degrees warmer than MacDill AFB, with only about six miles of open water separating the two.

The graphic below shows at least five different temperature gradient colors, with light blue being the coldest. West Tampa and N.E. Pinellas being the coldest, but getting warmer going S.W into Pinellas.