Weather456's Tropical Weather Blog

Significant Weather Events and Weekly Tropical Report

By: Weather456, 3:32 AM GMT on August 31, 2007

Starting on Saturday 1 September 2007, my blog will feature reports on significant tropical weather events such as tropical cyclones, cloud formations, frontal development, extratropical developments, etc. In addition to that, every Sunday I will review the tropics and subtropics for the past week, addressing issues such as mean surface and upper tropospheric circulation patterns, anomalies and major weather events of that week. Images and illustrations will be available along with tables and interesting statistics on surface buoys, ships, land stations and aircraft reports.

This is aimed at summarising the tropics and subtropics for those who might of miss something or would like to review a past aspect. My first weekly report will be on the 9th of September and that will address the events of week 2-8 September 2007. My first significant weather report will most likely be the next major tropical/subtropical cyclone.

An example would be Subtropical Storm Andrea in May 2007

Extract from a report I did on Andrea back in June.

Andrea beginnings started late on 6 May, when an extratropical low and associated cold front became blocked by a high pressure system to the north across the Western Atlantic and East Canada. The low moved southwestward over relatively warm waters and quickly occluded, gradually wrapping convection around its centre (Figure 3). Early on 8 May, the occluded front associated with the system began to dissipate and convection became more consolidated and numerous. Furthermore, the cloud, rainfall and wind distribution of the system (Figure 5) was reminiscent of classic subtropical cyclones and it is believed that a subtropical low formed between 1200 UTC and 1800 UTC 8 May.



Figure 5. GOES-12 visible shot of developing Andrea at 2145 UTC 8 May 2007 and the inset of the surface pressure, wind and precipitation distribution at 1800 UTC 8 May 2007. Subtropical cyclones are characterized as having most of their intense clouds oriented in a ring around a cloud-free centre. They are also characterized as having their strongest winds being felt well away from the centre and two rainfall maxima in the northeast and northwest section of the storm. Andrea possessed all these characteristics on 8 and 9 May 2007.


Fire's In Greece; Dust in the Taklimakan

By: Weather456, 3:24 PM GMT on August 27, 2007

Fires in Greece

Deadly wildfires in southern Greece wafted thick clouds of smoke over the Ionian Sea and southward to the Mediterranean in late August 2007. This image of Greece was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on August 26, and places where MODIS detected actively burning fires are outlined in red. A line of fires stretches along the western coast of Greece’s Peloponnesus Peninsula. To the northeast, a large fire is casting a plume of smoke over Athens.

According to news reports from the British Broadcasting Corporation (BBC), at least 60 people had been killed by the fires as of August 27. Hundreds of homes had been burned and thousands had to evacuate. The government suspects that the fires were caused by arson, and it has declared a national emergency to deal with the situation.

The large image provided above has a spatial resolution (level of detail) of 250 meters per pixel. The MODIS Rapid Response Team provides twice-daily images of the region in additional resolutions and formats, including an infrared-enhanced version that highlights burn scars.

NASA image courtesy the MODIS Rapid Response Team, Goddard Space Flight Center




Dust in the Taklimakan



Dust blew eastward out of the Taklimakan Desert on August 22, 2007. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite took this picture the same day, capturing beige dust plumes snaking their way out of the desert basin as bright white clouds hover overhead. The dust plumes mirror the color of the underlying desert basin. In contrast, the rugged topography of the surrounding mountains is darker. Mountains in the north sport green vegetation and even some snow cover, which forms a dendritic pattern compared to the billowy clouds.

One of the world’s largest sandy deserts, the Taklimakan (or Takla Makan) lies in the Tarim Basin, sandwiched between the Tien Shan Mountains to the north and Kunlun Mountains to the south. A vegetation-lined river flows from the Tien Shan Mountains southeastward into the northern part of the basin. Water flowing into the basin finds no outlet, and over the years, water-deposited sediments have steadily accumulated. In some places, the sand cover is as much as 300 meters (roughly 1,000 feet) thick. Opinions varied about the desert’s age, some dating it in the middle of the Pleistocene, less than a million years old. A 2006 study, however, concluded that sand dunes were shifting in the Taklimakan by 5.3 million years ago.

Home to little plant life, the Taklimakan sees a wide range in temperatures characteristic of sandy deserts. Summertime temperatures can soar to 38 degrees Celsius (100 degrees Fahrenheit), especially along the desert’s eastern edge. The dearth of vegetation and extreme heat create conditions in the lower atmosphere that increase the likelihood of dust storms.

All this information came from the The Earth Observatory Center - Natural Diasters.

Floods in the Midwestern United States

By: Weather456, 4:59 PM GMT on August 23, 2007

Water levels on the Blanchard River in northwestern Ohio reached near-record levels a short time after the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured the top image at 12:30 p.m. Eastern Daylight Time, on August 22, 2007. At 1:00 p.m., National Weather Service gauges in Findlay, Ohio, recorded water levels of 18.46 feet, just under six and a half inches short of the record crest of 18.5 feet set on March 13, 1913. In both cases, the river rose more than seven feet above its flood stage of 11 feet. The August 22 flood swamped the city of Findlay, forcing hundreds from their homes and putting the city in a state of emergency, reported the Associated Press on August 23.

The disastrous floods along the Blanchard River can be seen in the top image. The image was made with a combination of visible and infrared light to increase the contrast between water and land. Water is dark blue or black, while plant-covered land is bright green. Tiny squares of plant-free land, most like fallow fields in this case, are tan. Cities are gray, looking like a dark smudge against the bright green landscape. Lingering clouds are light blue and white.

The severity of the flood can be gauged by comparing the top image with the lower image, which was taken on August 13, 2007. In the lower image, the Blanchard River is too small to be visible. By August 22, the river and many of its tributaries are clearly visible. The river expands over Findlay, and then bends south.

Ohio was not the only state that experienced floods in mid-August. A string of severe thunderstorms dumped heavy rain on several Midwest states, including Minnesota, Wisconsin, Iowa, Illinois, Indiana, and Ohio. At the same time, the remnants of Tropical Storm Erin triggered deadly flooding in Oklahoma and Texas.

These images are shown at MODIS’ maximum resolution of 250 meters per pixel. Daily images of the U.S. Midwest are available from the MODIS Rapid Response System in a variety of resolutions.

NASA images courtesy the MODIS Rapid Response Team at NASA GSFC.

By Earth Observatory

Tropical Cyclone Formation Discussion

By: Weather456, 1:26 PM GMT on August 23, 2007

The below is report is a review of current conditions in the Atlantic as of 1200 UTC 23 August 2007. This review is organize under six headings, the requirements for tropical cyclone formation.

Mid-Low Level Moisture

The bulk of the moisture is situated in the Caribbean Sea, the Southern Gulf of Mexico and near the Inter tropical Convergence Zone, with dry air in Northern Gulf of Mexico, the Subtropical Central and Eastern Atlantic north of 15N. This is based on 1000-500 mb relative humidity.

Sea Surface Temperatures (SSTs)

SSTs are above 26Ceveryhwere except for the subtropical Atlantic east of 40W north of 18N. Highest temperatures in the Western Caribbean and Gulf of Mexico. Lowest in the Southwest North Atlantic with variations near the coast of northern South America and the US.

Relative Vorticity and Surface Convergence

Maxima is south of 15N over Central America, Northeastern South America and the ITCZ near 50W and 40W. Minima in the Tradewind belt, most of the Caribbean and Gulf of Mexico. A secondary maxima in the Mid-Latitudes north of 30N.

Wind Shear

Wind shear above 20 Knots to the southeast of two upper lows across Cuba and the central Atlantic north of 15N.

Low Level Disturbances

A tropical wave in the western Caribbean and the Atlantic ITCZ.

Instability

Greatest instability per 850 mb Theta-E and 700 mb Lifted Index correspond with the SSTs with the greatest instability in the Gulf of Mexico, Caribbean Sea and Western Atlantic and along the ITCZ. Stability in the Subtropical East Atlantic.


Figure 1 GFS 850 MB Theta-E Chart



Figure 2 SSD Vertical Instability (C)



I'll post more charts during the day.

W456

Tropical Weather Update

By: Weather456, 10:04 PM GMT on August 16, 2007

NORTH ATLANTIC TROPICAL WEATHER SUMMARY
WEATHER456, BASSETERRE, SAINT KITTS, WEST INDIES
4:38 PM AST THURSDAY, AUGUST 16, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 1800/1800 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 2015 UTC...

....SYNOPSIS....

GULF OF MEXICO/ATLANTIC OCEAN WEST OF 60W....

AN UPPER RIDGE COVERS THE SOUTHEAST UNITED STATES AND ENTIRE GULF OF MEXICO WITH AN UPPER LEVEL TROUGH/LOW TO THE NORTHEAST OF THE CENTRAL BAHAMAS. REMNANTS OF ERIN CONTINUES TO MOVE ACROSS CENTRAL TEXAS BRINGING SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS. ADDITIONAL SHOWERS HAVE DEVELOP OVER THE EAST GULF UNDER DIFFLUENT FLOW ASSOCIATED WITH THE UPPER HIGH.

A SURFACE RIDGE OVER THE AREA IS PROVIDING FAIR WEATHER AND LIGHT TO MODERATE TRADES FROM 90W TO 60W. SCATTERED SHOWERS ARE NEAR 69W NORTH OF 23N ASSOCIATED INSTABILITY EAST OF THE UPPER TROUGH/LOW. OTHERWISE FAIR WEATHER DOMINATES.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

WINDS ACROSS THE CARIBBEAN ARE RATHER BREEZY THIS EVENING MOST LIKELY DUE TO THE PRESSURE GRADIENT BETWEEN THE LARGE SUBTROPICAL RIDGE TO THE NORTH AND APPROACHING HURRICANE DEAN. THESE WINDS ARE SUPPORTING EMBEDDED CLOUDS/SHOWERS ACROSS SOME PARTS MOSTLY NOTABLY IN THE CENTRAL/WESTERN CARIBBEAN. IN ADDITION...HIGH RESOLUTION VISIBLE SHOTS FROM NEXSAT DEPICTS AFTERNOON CUMULONIMBUS CLOUDS OVER CENTRAL AMERICA, CUBA, JAMAICA AND HISPANIOLA WITH LIGHTNING DATA SUGGEST POSSIBLE THUNDERSTORMS ACROSS PANAMA.

A TROPICAL WAVE IS ALONG 69W SOUTH OF 17N MOVING WEST NEAR 15 KNOTS. THIS WAVE CONTINUES TO BE VOID OF MUCH CONVECTION WITH A LITTLE SURGE OF MOISTURE MOVING THROUGH THE CARIBBEAN.

ACROSS THE EASTERN CARIBBEAN MAINLY FAIR WEATHER EXIST BUT PASSING SHOWERS ARE BEING REPORTED IN SAINT KITTS SO THERE IS SOME CHANCE OF NON-HURRICANE SHOWERS ACROSS THE LEEWARD ISLANDS BEFORE DEAN GETS HEAR. ON THE OTHER HAND...THE OUTER BANDS OF DEAN ARE AFFECTING THE WINDWARD ISLANDS...PARTICULARLY BARBADOS. LATEST OBSERVATION OUT OF GRANTLEY ADAMS, BARBADOS AS OF 5 PM AST SHOWED WINDS AT 15 MPH OUT OF THE NNE WITH LIGHT RAIN AND A PRESSURE OF 1009 MILLIBARS. THE 24 HRS PRESSURE TENDENCY IS -2.0 MILLIBARS AS DEAN INCHES EVER SO CLOSE.

SOME OF THE STRONGEST BUOY OBSERVATION REPORTED NEAR DEAN

49.9 KNOTS – 41101 – 1900 UTC
27.7 KNOTS – 41100 – 1900 UTC
40.8 KNOTS – 41040 – 1250 UTC

A MORE COMPREHENSIVE UPDATE OF DEAN TONIGHT.

$$
WEATHER456

Hurricane Dean

By: Weather456, 1:10 PM GMT on August 16, 2007

Hurricane Dean Update

As of 1215 UTC Dean was located near 13.5N/53.3W moving west near 24 mph. Winds estimated by the NRL is 75 knots while T numbers from SSD support 77 knots whicch indicate Dean maybe stronger than the 8am advisory.

Dean went under quick organziation overnight with the formation of small eye that clouded over a few times. The storm has also grown in size which means a larger area will be affected across the Islands.

Warnings and wathes have already been issued for some islands as Deab is expected to reach them some time on Friday. I will try to update more often briging current conditions and webcams from the islands through out the day and on Friday.

by Weather456

Tropical Update

By: Weather456, 12:33 AM GMT on August 16, 2007

NORTH ATLANTIC TROPICAL WEATHER DISCUSSION
Weather456, BASSETERRE, SAINT KITTS, WEST INDIES
6:20 PM AST WEDNESDAY, AUGUST 15, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 1800/1800 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 2315 UTC...

SPECIAL TROPICAL/SUBTROPICAL SYSTEMS....

AS OF 2145 UTC TROPICAL STORM ERIN WAS LOCATED NEAR 26.0N/93.8W MOVING TO THE NORTHWEST NEAR 13 MPH. WINDS ARE 35 KNOTS AND PRESSURE REMAIN AT 1005 MILLIBARS.

CURRENT SURFACE OBSERVATIONS AND LATEST QUIKSCAT SUPPORT THIS CURRENT INTENSITY ALONG WITH T NUMBERS FROM THE SSD. THE STRONGEST WIND REPORTED SO FAR WAS 21.1 KNOTS FROM BUOY 42019 NEAR 29.9N/995.3W.

SATELLITE IMAGERY INDICATE THAT CONVECTION WITH ERIN IS WARMING AND EXPANDING DUE TO PRONOUNCE OUTFLOW...BUT THE CENTRE OF CIRCULATION REMAINS UNDER THE SOUTH EDGE OF THE CENTRAL DENSE OVERCAST.

WIND SHEAR REMAINS LOW AND SEA SURFACE TEMPERATURES ARE WARM SO ERIN COULD REACH AT LEAST 45 MPH BEFORE LANDFALL IN SOUTH TEXAS IN THE NEXT 24 HRS. RADAR IMAGERY ALREADY SHOW BANDS OF SHOWERS AFFECTING THE COAST OF TEXAS. WAVES ARE EXPECTED TO BE NEAR 10 FT IN EASTERLY SWELLS BEGINNING TONIGHT. PLEASE REFER TO YOUR LOCAL WEATHER OFFICE FOR MORE INFORMATION.

TROPICAL STORM DEAN IN THE CENTRAL ATLANTIC NEAR 12.8N/47.0W MOVING WEST-NORTHWEST NEAR 21 MPH. WIND ARE NEAR 55 KNOTS AND PRESSURE IS DOWN TO 994 MB AS OF 2315 UTC. SATELLITE IMAGERY SHOWS WELL DEFINE BANDING FEATURE WITH DEAN WITH THE CENTRE UNDER A DEFINE CDO. THE MOST INTERESTING ASPECT OF DEAN IS THE CURRENT MOVEMENT VERSUS THE 5 PM NHC TRACK. THERE IS A LOT OF CLASHING AND UNCERTAINTIES BUT I THINK THE TRACK WILL SHIFT A LITTLE FURTHER NORTH AT 11 PM.

....SYNOPSIS....

GULF OF MEXICO/ATLANTIC OCEAN WEST OF 60W....

A VERY LARGE UPPER RIDGE IS OVER THE SOUTHEAST UNITED STATES AND THE ENTIRE GULF SUPPORTING A RELATIVELY DRY AIRMASS AND FAIR SKIES ACROSS MOST PARTS OVER LAND. A LARGE MOIST AIRMASS COVERS THE ENTIRE GULF ASSOCIATED WITH TROPICAL STORM ERIN WEST OF 90W AND THUNDERSTORMS EAST OF 90W ASSOCIATED WITH DIFFLUENT FLOW FROM THE OUTFLOW FROM ERIN. AT THE SURFACE A LIGHT TO MODERATE WIND FLOW IS A RESULT OF WEAK SURFACE PRESSURE PATTERN. SOME STRONGER WINDS IS POSSIBLE SHOWERS AND THUNDERSTORM SQUALLS.

A UPPER LOW IS OVER THE WEST ATLANTIC WITH ITS AXIS 70W-75W WITH AN EMBEDDED UPPER LEVEL LOW NEAR 28N/71W. FAIR WEATHER ACCOMPANIES THIS TROUGH EXCEPT FOR A FEW MULTILAYERED CLOUDS AND POSSIBLE SHOWERS NEAR 70W-60W EAST OF THE AXIS IN THE DIFFLUENCE FLOW. ELSEWHERE...THE WEST EXTENSION OF THE AZORES HIGH CONTINUES TO BUILD OVER THE ATLANTIC PROVIDING MODERATE ANTICYCLONIC FLOW AND ENHANCING STABILITY.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

THE ONLY SHOWER ACTIVITY OVER THE CARIBBEAN TONIGHT IS OVER LAND...CENTRAL AMERICA, CUBA, AND HISPANIOLA...DUE TO INSTABILITY CAUSED BY SEA BREEZES AND DAYTIME HEATING. THE CARIBBEAN SEA REMAINS IN AN EASTERLY TRADE REGIME AND RELATIVELY DRY AIR RESULTING IN FAIR SKIES TONIGHT.

$$
Weather456

Dean On Its Way to Hurricane Strength

By: Weather456, 4:27 PM GMT on August 15, 2007

Tropical Storm Dean is well on its way to becoming the first hurricane of the 2007 Atlantic Hurricane Season. Satellite analysis reveals wind shear has relax significantly and the center is well under the deepest convection (see below) with an uniform CDO cloud region.

Microwave data from the NRL show banding features with a possible eye forming. I expect T numbers to gradually increase and Dean could be 65-70 mph by 5pm and a hurricane by 11 am on Thursday. The forecast track have not change much from 12 hrs ago and the system is foreast to reach the Central Antilles by midday Friday if the forecast holds true.



Tropical Depression Five: Erin?

By: Weather456, 11:17 AM GMT on August 15, 2007

What started out as an upper low north of Hispaniola interacting with a series of Caribbean tropical waves is now in the Central Gulf...strenghtening into a tropical storm.

The storm brought showers from Hispniola, the Turks, The Bahamas, Cuba, Jamica, parts of Central America and now Northern Mexico/Southern Texas is next.

Satellite imagery this morning shows a well define CDO has develop with this system and T numbers have increase to 2.5 or 40 mph. Quikscat pass from 2:05 UTC Wednesday support 40 knot winds but in rain contaminated barbs. Surface observations also indicated a tight core of 35-40 knot winds...which was not the case 24 hrs ago with a broad wind field...which further suggest development.

Not Much With Dean or 91L

By: Weather456, 11:38 PM GMT on August 14, 2007

NORTH ATLANTIC TROPICAL WEATHER DISCUSSION
WEATHER456, BASSETERRE, SAINT KITTS, WEST INDIES
7:07 PM AST TUESDAY, AUGUST 14, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 1800/1800 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 2145 UTC...

SPECIAL TROPICAL/SUBTROPICAL SYSTEMS....

NONE

....SYNOPSIS....

GULF OF MEXICO/ATLANTIC OCEAN WEST OF 60W....

A FRONTAL BOUNDARY EXTENDS FROM EASTERN GEORGIA ACROSS THE SOUTHEAST UNITED STATES TO CENTRAL ARKANSAS. MEANWHILE A LARGE UPPER HIGH IS CENTRED OVER ARKANSAS AT 35N/99W WITH RIDGING FROM 90W TO NEAR 80W FROM 47N TO 15N...COVERING THE MOST OF THE EASTERN UNITED STATES, THE GULF OF MEXICO AND NORTHERN CENTRAL AMERICA. THE HIGH CONTINUES TO ASSOCIATED WITH STABLE AIR AND LITTLE SHOWER ACTIVITY IS UNDER THE RIDGE. THE CURRENT FORECAST CALLS FOR THE HIGH TO REMAIN STATIONARY FOR THE NEST 24 TO 48 HRS LIMITING SHOWER ACTIVITY. THE ONLY PRECIPITATION SHOULD COME FROM 91L INVEST IN THE CENTRAL GULF AND FEW STRAY SHOWERS FROM DAYTIME INSTABILITY AND THE LOW LEVEL JET.

SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE OVER THE GULF OF MEXICO ASSOCIATED WITH A 1006 MB LOW NEAR 23N/91W MOVING OFF THE WNW/NW. DESPITE INCREASE IN SSD DVORAK T NUMBERS SURFACE OBSERVATIONS INDICATE WIND NO MORE THAN 20 KNOTS. THE HURRICANE HUNTER FLIGHT THIS AFTERNOON MEASURE MAXIMUM FLIGHT LEVEL WINDS OVER 23 KNOTS AT 240 METERS ABOVE SEA LEVEL AND MINIMUM MEASURE PRESSURE WAS 1006 MB. THEY DID NOT FIND ENOUGH EVIDENCE TO UPGRADE WITH TO A TROPICAL SYSTEM. NEVERTHELESS...DEVELOPMENT IS STILL ANTICIPATED AS CONDITIONS BECOME MORE FAVOURABLE.

A SHARP UPPER TROUGH IS OVER THE ATLANTIC WITH ITS AXIS NEAR 70W-80W NORTH OF 25N. THE ASSOCIATED SURFACE TROUGH IS PUSHING SOUTHEAST ACROSS THE AREA ACCOMPANIED BY A SWATH OF SHOWERS EXTENDING FROM SOUTH FLORIDA/THE NORTHERN BAHAMAS NORTHEASTWARD OVER BERMUDA INTO THE NORTH ATLANTIC. EXPECT THE SYSTEM MOVE SLOWLY OVER THE ATLANTIC THEN DISSIPATE. ELSEWHERE...FAIR WEATHER IS NOTED.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

NO SIGNIFICANT SURFACE FEATURE OVER THE CARIBBEAN THIS AFTERNOON. TRADES REMAIN THE LIGHT SIDE...INCREASING AS ONE GOES WEST WHERE THE PRESSURE GRADIENT BECOMES TIGHTER BETWEEN THE SUBTROPICAL RIDGE TO THE NORTH AND THE LOW ASSOCIATED WITH 91L SHOWERS ARE OVER THE EXTREME NORTHWEST CARIBBEAN FROM THE EFFECTS OF 91L. FURTHER SOUTH...TYPICAL SHOWERS ARE OVER THE SOUTHWEST CARIBBEAN AND ADJACENT LANDMASSES WHERE THE EASTERN PACIFIC MONSOON TROUGH LIES.

A UPPER TROUGH IS OVER THE EASTERN CARIBBEAN...FAIR WEATHER IS EVERYWHERE FROM 70W TO 50W IN THE TROPICAL ATLANTIC.

TROPICAL ATLANTIC....

TROPICAL STORM DEAN CONTINUES TO CHURN IN THE CENTRAL ATLANTIC. RECENT SATELLITE IMAGERY INDICATE THE SYSTEM STILL HAS MAINTAIN ITS BANDING (SPIN) BUT IS DEVELOPING SLOWLY...SO I’M NOT GOING TO DAY MUCH ABOUT IT UNTIL I SEE SOME MAJOR SIGHS OF EITHER DEVELOPMENT OR WEAKENING.

$$
WEATHER456

91L: Next Depression?

By: Weather456, 1:30 PM GMT on August 14, 2007

Satellite imagery and surface observation indicate that an area of low pressutre in the Southeast Gulf has become slighty better organize with a close low level vortex now evident. However the system remains disorganize at this point due unfavorable upper level winds and convection is rather weak but these winds should relax and along with 28-30 degree celcius waters...a tropical depression could form in the next 24 hrs. Dvorak intensities from the SSD remain at 1.0 or 30 knots.

The current forecast track takes the system towards the northwest becoming a threat to Mexico or Texas. Some models are predicting a category one hurricane but I am seeing a 60 knot tropical storm if it does manages to develop.

Weather456's Tropical Weather Discussion: 11 PM

By: Weather456, 3:09 AM GMT on August 14, 2007

NORTH ATLANTIC TROPICAL WEATHER DISCUSSION
WEATHER456, BASSETERRE, SAINT KITTS, WEST INDIES
10:54 PM AST MONDAY, AUGUST 13, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 1800/0000 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 0145 UTC...

SPECIAL TROPICAL/SUBTROPICAL SYSTEMS....

AN UPPER LOW IS CENTRED NEAR 27N/91W. SHOWERS CONTINUE IN THE SOUTHEASTERN GULF OF MEXICO WHERE THE UPPER LEVEL LOW INTERACTING WITH A TROPICAL WAVE ALONG 86W. SURFACE OBSERVATIONS CONTINUE TO INDICATE A BROAD AREA OF LOW PRESSURE CENTRED ON 1007 MILLIBAR LOW NEAR 23N/83W. OBSERVATION ALSO INDICATE 20-25 KNOTS WHICH IS IN FAIR AGREEMENT WITH THE CURRENT T NUMBERS FROM SSD. SEA SURFACE TEMPERATURES ARE MORE THAN FAVOURABLE TO SUPPORT DEVELOPMENT BUT 20-30 KNOTS OF SHEAR IS IMPEDING DEVELOPMENT BUT IS FORECAST TO BECOME MORE FAVOURABLE. CURRENT FORECAST TRACK IS TO HEAD WEST-NORTHWEST TOWARDS CENTRAL MEXICO/TEXAS.

TROPICAL DEPRESSION FOUR IS CENTRED NEAR 12.0N/34.2W MOVING WEST NEAR 17 KNOTS AS OF 0145 UTC. DESPITE INCREASE CURVE BANDING FEATURES WITH THIS SYSTEM., THE CENTRE OF CIRCULATION REMAINS THE EASTERN EDGE OF THE DEEP CONVECTIVE MASS AS SOME EASTERLY SHEAR CONTINUES TO AFFECT IT. CONDITIONS STILL ARE FORECAST TO BECOME MORE FAVOURABLE FOR ADDITIONAL ORGANIZATION AND A TROPICAL STORM COULD FORM IN NEXT 12 HRS. DVORAK T NUMBERS HAVE NOT CHANGE AND REMAIN AT 2.0 OR 30 KNOTS. I DON’T THINK THE FORECAST TRACK WILL CHANGE MUCH FROM 5 PM AND THE LEEWARD ISLANDS STILL SHOULD CLOSING MONITOR IT.

....SYNOPSIS....

GULF OF MEXICO/ATLANTIC OCEAN WEST OF 60W....

SCATTERED SHOWERS ARE OVER THE SOUTHEASTERN UNITED STATES AS THE UPPER LEVEL HIGH THAT PROVIDED THAT DRY STABLE AIRMASS FOR THE PAST FEW DAYS MOVES INTO ACROSS THE WESTERN UNITED STATES NEAR 38N/104W.

SHOWERS OVER THE GULF ARE ASSOCIATED WITH THE INTERACTING BETWEEN AN UPPER LEVEL LOW AND A TROPICAL WAVE. SEE ABOVE.

SCATTERED SHOWERS EXTEND FROM THE CENTRAL BAHAMAS ALONG 30N/70W 33N/60W TO BEYOND 40N/50W. THIS ACTIVITY IS ASSOCIATED WITH A SURFACE WARM FRONT THAT STRETCHES ACROSS THE AREA AND A SERIES OF ATTACHED LOWS.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

THE MOST ACTIVE WEATHER IN THE CARIBBEAN TONIGHT REMAINS WEST OF 70W. FIRST...A TROPICAL WAVE EXTENDS FROM THE SOUTHEAST GULF ALONG 86W ACROSS CENTRAL AMERICA INTO THE EASTER PACIFIC. SHOWER COVER THE WEST FROM 80W TO 90 NORTH OF 15N. FURTHER SOUTH...A SURFACE TROUGH IN CONJUNCTION WITH THE EASTERN PACIFIC MONSOON TROUGH IS ENHANCING VIGOROUS CONVECTION EXTENDING FROM NORTHWEST COLOMBIA ACROSS PANAMA AND COSTA RICA COMBING WITH THE EFFECTS THE WAVE OVER NICARAGUA.

UPPER TROUGH CONTINUES PROVIDE FAIR TO PARTLY CLOUDY SKIES OVER THE EASTERN CARIBBEAN. SHOWERS REMAIN MINIMAL OR ABSENT.

TROPICAL ATLANTIC....

THE SURFACE AZORES RIDGE CENTRED ON A 1025 MB HIGH NEAR 32N/33W IS PROVIDING FAIR WEATHER AND MODERATE TRADES OVER THE ENTIRE TROPICAL ATLANTIC.


WEATHER456

Tropical Depression Four and Invest 91L: Double Trouble

By: Weather456, 7:38 PM GMT on August 13, 2007

Tropical Depression Four

As of 1815 UTC this afternoon…Tropical Depression Four was centered near 21.1N/30.7W moving off to the west near 18 knots. Winds are 35 mph and pressure is estimated to be 1005 millibars. Recent visible appearance show banding is the main feature and it is improving with little areas of convective bursts. The system continues to be affected by easterly shear with most of the convection to the west of the low level vortex. Nevertheless…the system is slowly developing and should be in more favorable conditions in the upcoming days.

Dvorak numbers from the Satellite Service Division (SSD) remain at 2.0 or 30 knots which further support slow development.

The current NHC track calls for it to continue west to west-northwest but this may shift further north at the 5 PM advisory. Landfall at this time is highly and I stress “highly” unclear this far out in the Atlantic but the Leeward Islands may be

Note:
A healthy storm can turn into a remnant low. Refer to Tropical Storm Chris of 2006

91L
Surface observations indicate that there is a surface circulation with activity caused by the interaction between a tropical and an upper low in the Eastern Gulf of Mexico. Convection still remains rather disorganize and limited at this point...BUT...if shear decreases as forecast...SSTs near 90 degrees in the Gulf of Mexico may build this system into a threat greater than TD 4.

Invest 91L


Current Surface Observation (Marine Only)


Tropical Depression 4: Trouble

By: Weather456, 1:46 PM GMT on August 13, 2007

Satellite obsverations continue to show increase organization in associated with a tropical wave in the Eastern Atlantic. Dvorak T# from the SSD indicate 30 Knots winds and the Navy Reasearch Laboratory is in agreement with NRL estimating a pressure down to 1005 millibars indicating a Tropical Depression has form near 12.1N/30.7W.

The enviroment around the depression is somewhat favorable for additiional development and a Tropical Storm could form later today or on Tuesday.

It is too early to really know who is threaten by this system but the Lesser Antilles is nearest to this system.

More as the day progresses.



Weather456's Tropical Weather Discussion 8AM

By: Weather456, 11:38 AM GMT on August 13, 2007

NORTH ATLANTIC TROPICAL WEATHER DISCUSSION
Weather456, BASSETERRE, SAINT KITTS, WEST INDIES
7:10 AM AST MONDAY, AUGUST 13, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 0600/0600 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 1015 UTC...

SPECIAL TROPICAL/SUBTROPICAL SYSTEMS....

DUE THE NAVY SITE BEING DOWN...DATA AVAILABILITY IS SCATTERED AN FRUSTRATING...MORE AS THE WAVES DEVELOP AND MOVES MORE WEST.

....SYNOPSIS....

GULF OF MEXICO/ATLANTIC OCEAN WEST OF 60W....

THE CONTINENTAL RIDGE IS CENTRED ON A 200 MB HIGH OVER NORTHERN TEXAS WITH RIDGING OVER MOST OF THE SOUTHERN UNITED STATES. SATELLITE IMAGERY SHOWS THE HIGH IS BLOCKING FRONTAL FEATURES AND THUS A DRY AIR MASS AND RATHER WARM WEATHER IS ASSOCIATED WITH THIS FEATURE. A 1017 MB HIGH IS OVER THE GULF NEAR 27N/89W PROVIDING FAIR TO PARTLY CLOUDY SKIES AND LIGHT WINDS OVER THE GULF OF MEXICO WATERS. THE ONLY SIGNIFICANT WEATHER IS THE UPPER LOW IN THE SOUTHEASTERN GULF WHICH IS SUPPORTING MID-HIGH LEVEL CLOUDS AND SHOWERS FROM EAST OF 90W NORTH OF 22N.

A LINE OF SCATTERED SHOWERS EXTENDS FROM 30N/78W TO NEAR 40N/50W ASSOCIATED WITH A STATIONARY FRONT ACROSS THE SOUTHWEST NORTH ATLANTIC. ELSEWHERE...SURFACE RIDGING IS MAINTAINING FAIR WEATHER.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

TRADES REMAIN ON THE MODERATE SIDE THIS MORNING OVER MUCH OF THE CARIBBEAN WITH THE STRONGEST OVER THE WESTERN CARIBBEAN DUE THE PRESSURE GRADIENT BETWEEN LOW PRESSURE THERE AND HIGH PRESSURE IN THE ATLANTIC. SHOWERS AND THUNDERSTORMS CONTINUE IN THE NORTHWESTERN CARIBBEAN WHERE A TROPICAL WAVE ALONG 85W AND AN ADJOINING SURFACE TROUGH TO THE NORTH IS INTERACTING WITH THE UPPER LEVEL LOW IN THE EASTERN GULF. EXPECT THIS DISTURBED AREA TO CONTINUE WEST BRINGING SHOWERS TO CENTRAL AMERICA, CUBA AND THE SOUTHERN GULF.

UPPER TROUGH DIPS INTO THE EASTERN CARIBBEAN FROM THE ATLANTIC TO NEAR 12N/70W...MAINTAINING FAIRLY DRY WEATHER THIS MORNING...WITH THE EXCEPTION OF HIGH CLOUDS BORDER SOUTH AND EAST OF THE TROUGH.

$$
Weather456

Weather456's Tropical Weather Discussion: 10AM

By: Weather456, 1:46 PM GMT on August 12, 2007

NORTH ATLANTIC TROPICAL WEATHER DISCUSSION
WEATHER456, BASSETERRE, SAINT KITTS, WEST INDIES
9:26 AM AST SUNDAY, AUGUST 12, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 0600/0600 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 1215 UTC...

SPECIAL TROPICAL/SUBTROPICAL SYSTEMS....

NONE

....SYNOPSIS....

GULF OF MEXICO/ATLANTIC OCEAN WEST OF 60W....

A BROAD UPPER RIDGE CENTRED OVER NORTHERN TEXAS AT 33N/82W WITH RIDGING OVER MOST OF THE CONTINENTAL UNITED STATES AND THE GULF WESTERN GULF WATERS. THE UPPER HIGH CONTINUES TO SUPPORT A DRY AIRMASS OVER THESE AREAS...AND ALONG WITH SURFACE RIDGING... RESULTING IN FAIR SKIES AND LITTLE SHOWER ACTIVITY. AN UPPER LOW IS WEAKENING OVER CENTRAL FLORIDA WITH LITTLE ASSOCIATED SHOWER ACTIVITY.

MEANWHILE...AN UPPER LOW ENTERING THE GULF OF MEXICO THROUGH THE FLORIDA STRAITS. THE LOW IS SUPPORTING SCATTERED SHOWERS OVER THE GULF EAST OF 90W AND SOUTHWEST ATLANTIC WEST OF 70W...WHICH INCLUDES THE FLORIDA PENINSULA AND THE BAHAMIAN ISLANDS.

A STATIONARY FRONT GOES FROM CENTRAL GEORGIA ACROSS THE ATLANTIC ALONG 32N/80W 33N/70W TO BEYOND 35N/65W. SCATTERED SHOWERS EXTENDS 115 NM ON EITHER SIDE OF THE FRONT.

THE SURFACE AZORES RIDGE CONTINUES TO THE PREDOMINATE WEATHER MAKER ACROSS THE SOUTHWEST NORTH ATLANTIC WITH FAIR WEATHER FROM 70W TO 50W NORTH OF 20N...WITH THE EXCEPTION OF NEAR 60W-52 NORTH OF 23N WHERE AN TUTT CIRCULATION LIES.

CENTRAL AMERICA AND THE CARIBBEAN REGION....

A TROPICAL WAVE IS ALONG 85W SOUTH OF 23N MOVING WEST AT ABOUT 10 KNOTS. DEEP CONVECTION LIES ALONG THE AXIS OVER NORTHWEST CARIBBEAN WATERS, HONDURAS AND NICARAGUA.

ANOTHER WAVE IS ALONG 75W SOUTH OF 22N MOVING WEST AT ABOUT 13 KNOTS. SHOWERS CONTINUES OVER CUBA, THE CAYMANS, JAMAICA AND HISPANIOLA AS THE WAVE INTERACTS WITH AN UPPER LOW TO THE NORTH. THIS AREA IS SHOWING LITTLE SIGNS OF DEVELOPMENT. EXPECT THIS DISTURBED AREA TO CONTINUE WEST BRINGING ADDITIONAL SHOWERS CUBA, CENTRAL AMERICA AND SOUTHERN GULF.

A TUTT EXTENDS INTO THE EASTERN CARIBBEAN FROM THE ATLANTIC BASING OFF NEAR 14N/65W. THE TROUGH IS PROVIDING DRY WEATHER OF THE LEEWARD ISLANDS AND PUERTO RICO BUT TYPICAL DIFFLUENT FLOW TO THE SOUTH AND EAST OF THESE TUTT IS PRODUCING A SWATH OF MOISTURE AND CLOUDS FROM NORTH VENEZUELA ACROSS THE WINDWARD ISLANDS INTO THE ATLANTIC OCEAN.

WEATHERCASTER

Caribbean Disturbance

By: Weather456, 11:38 AM GMT on August 12, 2007

Caribbean Update - 7:53 AM AST

Showers and thunderstorms continue over the Northwest Caribbean where a tropical wave is interacting with an upper level low in the Eastern Gulf. Satellite imagery show some organization of thunderstorm clusters with this system. However...reports from the Caymans and buoy 42056 show no evidence of falling pressure or cyclonic circulation. Nevertheless...heavy showers will spread across the Caymans, Cuba and Jamaica.

Weather456 's Tropical Weather Discussions: 7PM

By: Weather456, 11:34 PM GMT on August 11, 2007

NORTH ATLANTIC TROPICAL WEATHER DISCUSSION
WEATHER456, BASSETERRE, SAINT KITTS, WEST INDIES
5:21 PM AST SATURDAY, AUGUST 11, 2007

TROPICAL WEATHER DISCUSSION FOR NORTH ATLANTIC BASIN FROM CENTRAL AMERICA TO THE WEST AFRICAN COAST BETWEEN THE EQUATOR AND 35N. THE FOLLOWING INFORMATION IS BASED ON METEOROLOGICAL ANALYSIS/SURFACE OBSERVATIONS THROUGH 1800/1800 UTC AND SATELLITE IMAGERY/RADAR OBSERVATIONS THROUGH 2015 UTC...

SPECIAL TROPICAL/SUBTROPICAL SYSTEMS....

N/a

....SYNOPSIS....

GULF OF MEXICO

A BROAD 200 MB HIGH IS CENTRED OVER THE CENTRAL TEXAS NEAR 32N/92W. THIS HIGH IS SUPPORTING A VERY DRY STABLE AIRMASS AND SURFACE RIDGING ALLOWING FOR FAIR SKIES AND LIGHT WINDS OVER THE SOUTH-CENTRAL, SOUTH-EASTERN UNITED STATES AND MUCH OF THE GULF OF MEXICO. HOWEVER...INSTABILITY ASSOCIATED WITH UPPER DIFFLUENCE ALONG WITH A FRONTAL BOUNDARY/LOW, SURFACE INFLOW AND DAYTIME HEATING...IS ENHANCING SHOWERS OVER PARTS OF SOUTH-CAROLINA, GEORGIA AND THE FLORIDA PANHANDLE.

ATLANTIC OCEAN WEST OF 60W/ CENTRAL AMERICA AND THE CARIBBEAN REGION....

AN UPPER LOW NEAR 23N/98W IS NOW MOVING ASHORE ACROSS THE CENTRAL MEXICO BRINGING SHOWERS WITH IT. ANOTHER UPPER LOW IS CENTRED OVER THE NORTHERN BAHAMAS NEAR 25N/79W. THE LOW IS PRODUCING MODERATE SHOWERS FROM 82W TO 75W...WHICH INCLUDES SOUTH FLORIDA, CUBA AND HISPANIOLA. ACTIVITY ALSO EXTENDS FURTHER SOUTH IN THE CARIBBEAN WHERE THE LOW CONTINUES TO INTERACT WITH A TROPICAL ALONG 79W SOUTH OF 20N. SHOWERS COVER THE AREA FROM 85W TO 75W NORTH OF 15N...SOME LOCALISED STRONG ACTIVITY...POSSIBILITY THUNDERSTORMS EXIST OVER LAND WHERE THERE IS ENHANCEMENT FROM DAYTIME HEATING AND SEA BREEZES.

SHOWERS FURTHER SOUTH OF 15N OVER THE SOUTHWEST CARIBBEAN AND LOWER CENTRAL AMERICA/COLOMBIA IS ASSOCIATED WITH SOUTHERN EXTENSION OF THE TROPICAL WAVE AND THE MONSOON TROUGH.

A SECOND WAVE IS ALONG 70W SOUTH OF 22N MOVING WEST NEAR 16 KNOTS. WEATHER OVER THIS AREA OF THE CARIBBEAN IS LESS ACTIVITY THAN THE WEST WITH MID-LEVEL MOISTURE BEING ADVECTED BY SOUTHEAST WINDS ASSOCIATED WITH A TUTT IN THE CENTRAL ATLANTIC. LOW LEVEL SURGE ASSOCIATED WITH TRADE WIND SHOWERS AND THE ITCZ/NECZ WILL ALSO PERIODS OF BAD WEATHER.

SURFACE RIDGING OF THE AZORES HIGH IS PROVIDING FOR EXCEPTIONALLY FAIR SKIES WITH LITTLE OR NO SHOWER ACTIVITY OVER THE ATLANTIC.

TROPICAL ATLANTIC....

THE SURFACE AZORES HIGH IS ANALYSED 1026 MB NEAR 35N/33W PROVIDING FAIR WEATHER AND A MODERATE TRADES OVER THE TROPICAL ATLANTIC. A TROPICAL WAVE IS ALONG 49W SOUTH OF 19N MOVING WEST NEAR 20 KNOTS WITH THE ASSOCIATED SHOWER ACTIVITY ALONG THE ITCZ/NECZ BAND.

$$
WEATHER456


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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About Weather456

With a Bachelors Degree in Environmental Sciences (2009), began tracking tropical storms in 2002 and is now a private forecaster.