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National Weather Service Forecast OfficeHouston/Galveston, Texas | |||||
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What a Difference a Year Makes! By Charles Roeseler Weather patterns change from year to year. Some years, the change is imperceptible, while other years the change can be striking. The latter was the case this year. The months of May and June 1998 were very hot and dry while May and June 1999 were warm and wet. A comparison of May and June temperature and precipitation data will be provided for College Station, Galveston and Houston's Intercontinental Airport for the years 1998 and 1999. The differences between the two years are rather dramatic. College Station Data
Galveston Data
Houston Intercontinental Data
(Note: Above statistics are compiled through June 30, 1999.) The College Station average daily temperature was 4.5 degrees warmer in May 1998 than May 1999. June of 1998 was a sweltering 5.2 degrees warmer than June 1999. All four months examined had average daily temperatures above normal. What is really striking is the number of 90 and 100 degree days observed in 1998. College Station reached or exceeded 100 degrees 12 times in May and June of 1998. That plateau has not been reached so far this year. In 1998, the temperature reached or exceeded 90 degrees 47 times in the two month period. So far this year, the temperature has reached or exceeded 90 degrees 25 times. 13 temperature records were tied or broken during the two month period in 1998 while this year there has only been one temperature record set. So far this year, the highest temperature recorded at Easterwood Field was 94 degrees which occurred on June 6th. In 1998, 94 degrees was reached on May 7th and was reached or exceeded another 11 times before June 6th. Clouds and rainfall typically suppress warmer temperatures and that was certainly the case this year. The two month rainfall total (1998) for College Station was 0.11 inches while in 1999 the rainfall was 8.83 inches. Similar trends were observed at Houston. The average daily temperature was 2.1 degrees warmer in May 1998 than May 1999. In June, the difference was 3.6 degrees. There were 44 days last year which reached or exceeded 90 degrees during May and June. This year, 90 degrees has been reached or exceeded 32 times. 100 degree temperatures have not been reached this year, but in 1998 the century mark was reached twice. Clouds and rain helped keep temperatures cooler than last year but still above climatological normals. In 1998, rainfall in May and June totaled 2.91 inches while in the 1999, the two month rainfall was 9.39 inches. Galveston, a coastal site, has a climate greatly influenced by the gulf. Temperatures typically don't vary much from year to year. However, rainfall totals can vary dramatically. Despite, the strong drought much of Texas endured last year, Galveston received 9.45 inches of rain in May and June (1998). Much of the rain which fell in that period occurred on June 27th and 28th when a weak coastal trough of low pressure developed. Areas from Palacios to High Island received six to eight inches of rain from that system. Skies remained dry 50 miles or more inland. This year (non-drought), Galveston received 5.91 inches of rain. Rain fell on eight days during the two months in 1998. In 1999, rain occurred on 22 days. So despite the lack of rainfall parity between the two years, the 1999 rainfall totals were more beneficial to agricultural interests. Temperature differences between the two years was less than a degree but all four months had temperatures which averaged above climatological normals. A quick look at long range climate projections indicate that much of eastern Texas can expect rainfall to remain near normal levels while temperatures climb a degree or two above climatological normals. High temperatures in July and August are typically in the mid and upper 90s and average rainfall is 3 to 4 inches per month. These projections will be altered quickly if a tropical system should make a visit to southeast Texas later this summer.  The following is a list of rainfall data for many supplemental sites across southeast Texas.
1999 Hurricane Season .... Quiet So Far By Josh Lichter So far this hurricane season, through July 28th, there has been only one Atlantic basin tropical cyclone. Arlene originated in the subtropical Atlantic about 550 miles southeast of the island of Bermuda from a non-tropical disturbance...along the remains of a front...on June 11th. The disturbance strengthened and became a tropical storm the following day while drifting northward. Arlene threatened Bermuda with peak winds at 50 mph but passed about 100 miles to the east and did not significantly impact the islands. Arlene dissipated on the 18th to the northeast of Bermuda. Both the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center (CPC) and Dr. William Gray, professor at Colorado State University, continue to forecast an active 1999 hurricane season. On their June 16th forecast, the CPC said that most of the activity is expected to occur during the peak three months (August-October) of the season. On June 4th, Dr. Gray and his colleagues predicted that low latitude formations will dominate which will lead to a more active Caribbean and Gulf of Mexico basin. Dr. Gray is calling for fourteen named storms, nine of which become hurricanes. Four of the hurricanes are expected to reach intense status, which is category 3, 4, or 5 on the Saffir-Simpson hurricane scale. So far this season, systems that have come off the west coast of Africa have raced westward toward the Caribbean Sea and have not developed. The season is still young, and residents across Southeast Texas are still urged to closely monitor the tropics. Texas has not been struck by a hurricane since 1989, and the last major hurricane strike was from Alicia in 1983. Our office still gives hurricane preparedness talks to schools, businesses, and organizations that may be beneficial to you and your employees. If you are interested in one of thesepresentations, please contact our office at (281.337.5074) or by email at joshua.lichter@noaa.gov.
Hurricane Issues
By Bill Read The extremely active hurricane seasons since 1995 and data collected from them have provided researchers on hurricane preparedness insight on a number of key issues facing the United States. These issues and how we deal with them are of significant importance to citizens living along the Texas Coast. Jerry Jarrel, Director of the National Hurricane Center, presented these issues at the EHCMA sponsored Houston/Galveston Hurricane Workshop on May 7th. A short summary of the most important issues and how they relate to our area is presented below:
There are seldom easy solutions to these issues. But by maintaining an awareness of the problem and working to understand the complexity, we will be better prepared when the next major hurricane threatens our area.
El Niño and La Niña...Effects on Southeast Texas
By Gene Hafele What's the difference between El Niño and La Niña? El Niño and La Niña are extreme phases of a naturally occurring climate cycle referred to as El Niño/Southern Oscillation. Both terms refer to large-scale changes in sea-surface temperature across the eastern tropical Pacific. Usually, sea-surface readings off South America's west coast range from the 60s to 70s�F, while they exceed 80�F in the "warm pool" located in the central and western Pacific. This warm pool expands to cover the tropics during El Niño, but during La Niña, the easterly trade winds strengthen and cold upwelling along the equator and the West coast of South America intensifies. Sea-surface temperatures along the equator can fall as much as 7�F belownormal. Why do El Niño and La Niña occur? El Niño and La Niña result from interaction between the surface of the ocean and the atmosphere in the tropical Pacific. Changes in the ocean impact the atmosphere and climate patterns around the globe. In turn, changes in the atmosphere impact the ocean temperatures and currents. The system oscillates between warm (El Niño) to neutral or cold (La Niña) conditions on average every 3-4 years. What are the impacts of La Niña and El Nino in Southeast Texas? Most of the impacts usually occur from the Fall through the Spring time. During an El Nino event (1997-98) with the jet stream further south, Southeast Texas will experience above normal rain and somewhat cooler temperatures. This was pretty much the case during the winter of 97-98. In a La Niña episode with the jet stream removed further north drier than normal conditions along with warmer conditions will prevail. During the current La Niña episode our average monthly temperatures have been above normal since it began late last summer. Precipitation during the winter months of 98-99 were generally below normalbut many areas have received above normal rainfall during the late spring into the early summer. How often does La Niña occur? El Niño and La Niña occur on average every 3 to 5 years. However, in the historical record the interval between events has varied from 2 to 7 years. According to the National Centers for Environmental Prediction, this century's previous La Niñas began in 1903, 1906, 1909, 1916, 1924, 1928, 1938, 1950,1954, 1964, 1970, 1973, 1975, 1988, and 1995. These events typically continued into the following spring. Since 1975, La Niñas have been only half as frequent as El Niños. How is La Niña influencing the Atlantic and Pacific hurricane seasons? Dr. William Gray at the Colorado State University has pioneered research efforts leading to the discovery of La Niña impacts on Atlantic hurricane activity, and to the first and, presently only, operational long-range forecasts of Atlantic basin hurricane activity. According to this research, the chances for the continental U.S. and the Caribbean Islands to experience hurricane activity increases substantially during La Niña. Despite this increase in hurricane activity during La Niña episodes in the Atlantic Basin, the Texas Coast does not necessarily receive more storms in La Niña years. The hurricanes to make landfall along the Texas Coast were Chantal and Jerry in 1989 when we were transitioning from an El Niño in the early summer to a weak La Niña by the Fall of 1989. Hurricane Alicia...a category 3 hurricane that made landfall in 1983... occurred during a moderate El Niño condition. What impacts do El Niño and La Niña have on tornadic activity across the country? Since a strong jet stream is an important ingredient for severe weather, the position of the jet stream determines the regions more likely to experience tornadoes. Contrasting El Niño and La Niña winters, the jet stream over the United States is considerably different. During El Niño the jet stream is oriented from west to east over the northern Gulf of Mexico and northern Florida. Thus this region is most susceptible to severe weather. During La Niña the jet stream extends from the central Rockies east-northeastward to the eastern Great Lakes. Thus severe weather is likely to be further north and west during La Niña than El Niño. During the winter of 97-98 we experienced prolonged periods of severe weather from November into early March as the jet stream was positioned along the northern portion of the Gulf of Mexico. The state of Florida experienced one of the worst tornado outbreaks in recent history during this time period. The spring of 1999 was a relatively mild severe weather season for southeast Texas as the positioning of the jet stream maintained a more northerly position. Where can I find more information on La Niña? The Internet is the greatest source of information on El Niño, La Niña and weather and climate data. NOAA has created one primary web site that allows you to link to many other resources: http://www.elnino.noaa.gov. Specific information on La Nina predictions and other background is available at NOAA's Climate Prediction Center: http://www.cpc.ncep.noaa.gov. Information on NOAA's latest research initiatives is available from the Climate Diagnostic Center: http://www.cdc.noaa.gov/ENSO/. 
Heat Safety Rules About 175 people die in this country every year due to excessive heat. When the Heat Index gets above 90 then it is time to take some precautions:
Tropical Funnels and Waterspouts By Richard Hitchens The summer months in southeast Texas are notorious for being hot and humid. Heat and humidity near the surface cause the atmosphere to become unstable, which leads to enhanced potential for parcels of air to rise and cool. Rising and cooling air, with sufficient moisture, can turn into clouds, showers and even thunderstorms. On otherwise quiet weather days, the vertical motion associated with clouds and showers can become quite strong, especially around boundaries near the surface between differing air masses. The upper Texas coastline acts as an almost permanent airmass boundary during the summer months. During the morning, land areas heat up very rapidly. The Gulf coastal waters, by contrast, undergo only a very slow rise in temperature through the mid summer months, and change very little temperature-wise during the course of one day. During the morning, a front develops along the coastline and moves inland through the afternoon. Forecasters refer to this front as a "seabreeze front". It is not uncommon for showers and thunderstorms to develop along the seabreeze front. Winds will shift slightly and increase in speed when the seabreeze front passes by. This is an indication of low level wind shear around the front. This, combined with the instability of the atmosphere during the summer, will cause the rising currents of air near the front to begin to rotate. In spots where the rising motion is especially vigorous, a funnel cloud can form. Luckily, these funnel clouds do not normally last very long and only rarely will touch down. Wind speeds are normally no higher than 40 to 70 mph. Two tropical funnel touchdowns were reported in the area in early June. One touched down briefly on the east side of downtown Houston on the 8th and damaged a warehouse. On the 9th, a touchdown was reported in Surfside along County Road 257. No damage occurred. Another weather phenomenon associated with a tropical environment is the waterspout. The waterspout is basically a tornado over the water. Showers will sometimes form over the Gulf waters due to high instability and can eventually grow into thunderstorms. While the showers are developing, intense updrafts can occur, feeding moisture and unstable air into the developing rain area. At the same time, downdrafts begin to occur in the area where rain is falling. The dividing line between the updraft and downdraft is referred to by forecasters as an "outflow boundary". This boundary can sometimes lead to the formation of brief waterspouts. Waterspouts can be very dangerous for mariners because they produce a sharp increase in wind speeds, sometimes higher than 50 knots. Waterspouts in the past have caused boats to capsize and have produced fatalities. Infrequently, a waterspout will move inland and produce damage. This occurred this past July 12th in Texas City. A waterspout moved inland briefly, and tore a roof from a section of an apartment building and produced minor damage to some adjacent properties. Luckily, there were no injuries. When you are out on the water, you should keep an "eye to the sky" when you see cumulus clouds beginning to develop vertically. This is a favored area for waterspouts to eventually form. If you see a spout, move away from it quickly. Tropical waterspouts usually do not move faster than 20 mph, so moving rapidly away from them on the open water is your best way to stay safe. Waterspouts normally last between two and twenty minutes. Tropical funnels and waterspouts produce lower wind speeds than tornadoes and severe thunderstorms. Tornadoes, in contrast to waterspouts and tropical funnels, form at the base of large rotating thunderstorms, known as mesocyclones, and can pack winds in excess of 200 mph. One disadvantage of tropical funnels and waterspouts is that they are very hard to detect on radar because they are small, short-lived, and rotation is confined to the very low levels of the atmosphere. A visual sighting is usually the only method the NWS has for issuing a warning or statement for a tropical funnel or waterspout. Over the upper Texas coastal waters, the favored period for formation of tropical waterspouts is during the mid and late morning through early afternoon. 
CO-OP CORNER By Don Oettinger We would like to express our sympathy to the family and friends of Ross Madole. Mr. Madole was the cooperative observer in Madisonville for over forty years. In 1985 he received the John Campanius Holm Award from the National Weather Service for "26 years of public service to his community and state for observing and recording temperature and rainfall data for Madisonville, Texas".
OBSERVING TIPS
When filling out the WS Form B-91 it is important to record the temperature and/or rainfall data on the correct date. This data should be recorded on the date that the readings are taken, not necessarily the date on which they occurred. For example, if you are taking a reading on the morning of the 2nd, the values that you read should be recorded on the line of the B-91 for the second day of the month. Even though the high temperature and possibly the rainfall actually happened on the 1st, it is still written on the 2nd. Most cooperative observers take their readings in the morning. The National Climatic Data Center is aware of the times the readings are taken and when they publish your data, the high temperature that is recorded on the 2nd day of the month is published as the high for the 1st. Please keep this in mind when filling out the B-91s. If the readings are entered on the wrong day the data will be skewed when received by NCDC and possibly not published. If you have any questions, need supplies, or have equipment problems please call Tom or Don at (281.337.5074). If you don't have our 800 number we'll be glad to give it to you. You can also email us at tom.fountain@noaa.gov or don.oettinger@noaa.gov. Thanks for your continued support of the Cooperative Observing Program. 
Severe Weather Update By Brian Kyle The New Year's Day tornado outbreak was covered in the last edition of Storm Signals. Since then, southeast Texas has seen a somewhat active late winter/spring severe weather season compared to the previous couple of years. Over 325 Severe Thunderstorm/Tornado/Flash Flood Warnings have been issued for the first 6 months of the year. To date, every single county (23 total) that this office warns for has reported some type of hail/wind/flood damage. Polk, San Jacinto and Trinity counties have been particularly active with a total of 43 combined reports of damage. Since all of the severe weather events cannot be covered in this short amount of space, highlights of the most significant storms are described below. On January 22nd, a supercell thunderstorm moved directly over the Bryan/College Station area. Though no tornadoes were reported, very large hail fell across that region causing damage to windows, roofs, and cars. Widespread reports of golfball sized hail were common. Some stones as large as softballs fell on northern portions of the Texas A&M campus. At last report, damage totals exceeded $10 million. Polk County suffered major flooding on March 13th and again on April 3rd. On the 3rd, a rainfall report called in from the Lake Livingston Dam indicated nearly 8.5 inches of rain fell in less than 4 hours! Needless to say, widespread flooding occurred and residents near Choates Creek in Livingston had to be evacuated from their homes. The region was declared a disaster area by Governor George W. Bush shortly thereafter. San Jacinto county also saw flooding that day with 6 to 9 inch rainfall totals. A weak line of storms moving in from the Hill Country rapidly strengthened along the southern I-45 corridor on May 10th. Winds in the 55-75 mph range were common as the squall line moved across causing structural damage to homes and businesses and blowing down powerlines and trees. There were also some short lived tornadoes between Alvin and Pearland. The hardest hit was the Houston metropolitan area, though quite a bit of damage was also reported in Fort Bend, Montgomery, Brazoria, Galveston and Liberty Counties. Hopefully, we'll have a quiet summer and keep the longest record of not being hit with a hurricane intact! 
Houston Chapter of the American Meteorological Society By Robert C. Van Hoven The annual election of officers was held last May. The new officers (with their phone and e-mail addresses) are:
Cecilia Sinclair works as a meteorologist for FOX TV 26. She was a previous president of the Local Chapter. Lew Fincher works for Dupont Chemical as a Hurricane Preparedness Specialist. Doris Rotzoll is a meteorologist at NASA's Space Meteorology Group. Dorri Breher works as a meteorologist for the Weather Research Center. Of interest, Lew was honored at the 21st National Hurricane Conference in Orlando, Florida on April 1 and was presented the 1999 Outstanding Achievement Award. He was recognized for organizing a hurricane preparedness safety program for the Dupont Chemical Plant in La Porte, Texas. This concept was expanded to other plants along the Gulf, Atlantic, and Caribbean coasts. This was further expanded to other petrochemical companies to the extent that he is now recognized as the "Founding Influence" in petrochemical hurricane preparedness along the U.S. Atlantic and Gulf coasts. The officer's planning meeting was held last June and meetings/speakers for the upcoming months are being lined up. The August meeting for all members will be on Thursday the 12th. It will be held at the Golden Corral at 12500 Gulf Freeway by Fuqua (713) 947-1162 . Time of dinner is 6 pm followed by the meeting. James R. Bailey of EQE International will talk about ways to mitigate wind damage to homes, businesses and industries. Lonny Farmer of Plylox will demonstrate a patented device called the Plylox clip which makes protecting windows and doors easier and faster.
EMWIN Houston
By Gene Hafele The Emergency Managers Weather Information Network (EMWIN) datastream is broadcast in the Houston area on 150.435 MHz. With the proper equipment, you can receive and display the EMWIN broadcast which includes virtually all National Weather Service text and graphic products, such as forecasts, watches, warnings, and hourly conditions from weather forecast offices in Texas, Oklahoma, and Louisiana. EMWIN Houston is a public service of the Harris County Appraisal District, Harris County Office of Emergency Management, the Texas National Guard, and the National Weather Service. The broadcast is supported by volunteer amateur radio operators who participate in RACES, the Radio Amateur Civil Emergency Service. The EMWIN datastream is received from the GOES 8 and 10 satellites by satellite dishes on top of the Harris County Appraisal District building near US 290 and Loop 610. Data of interest to users in the Houston area is then sent via a leased line data circuit to a 200 watt transmitter on top of the Exxon Corporation building in downtown Houston.To utilize this signal, you will need an IBM compatible computer, a VHF radio or scanner capable of receiving the FM data transmission on 150.435 MHz, an EMWIN demodulator, and software. There are no recurring costs involved. Depending on your distance from the transmitter site, a vertically polarized outside antenna (scanner or 2-meter amateur radio type) may be required. Generally, the signal is useful within a 35 to 40 mile radius of downtown Houston. This is the equipment you will need to properly utilize the EMWIN weather information: Computer: A minimum of a Pentium 100 computer with at least 32 MB of RAM running Windows 95/98/NT. Users must reserve 30 MB of hard disk space for the program and data files. The computer must have one free serial COM port and your video card must support 256 colors. Radio Receiver: Any standard VHF public service radio scanner with either a headphone or speaker output jack and a volume control, that is able to receive an FM signal at 150.435 MHz. Software: WeatherNode version 4.0 or RealEMWIN software and an EMWIN demodulator. Software and demodulators are available from commercial sources for less than $100 total. In addition to the VHF broadcast, EMWIN Houston's data is transmitted over the Internet by "push" broadcast. To receive the Internet datastream, the end user must install WeatherNode 4.0 software and the associated ByteBlaster client. The ByteBlaster should then be set for connection to 207.80.106.33. A demonstration version of WeatherNode 4.0 and ByteBlaster can be downloaded from the Wx4U website shown below. We recommend that users within range of the VHF broadcast receive the signal directly "off-the-air" since the broadcast datastream is not affected by Internet loading during periods of heavy use. Commercial Vendors The NWS uses radio, satellite and Internet broadcasts for disseminating the EMWIN data stream. RECEPTION and REPEATING of all broadcasts requires specialized equipment or software, available commercially (some for free). The following vendors supply software and/or general off-the-shelf hardware or specialized equipment useful for receiving and using EMWIN data.
Note: A listing here does not imply any particular endorsement by the Harris County Appraisal District, Harris County Office of Emergency Management, or NWS as to function or suitability for your purpose or environment. To other potential EMWIN vendors: If you would like to be listed here, please contact us and provide the pertinent details. Send details by e-mail to emwin-houston@emwin.hcad.org. For Additional EMWIN Information: http://iwin.nws.noaa.gov/emwin/index.htm | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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