wxmeddler Posted July 28, 2011 Share Posted July 28, 2011 Also of interest is the extremely low dewpoint, only 8C. I was about to add that. There is a nice 25°F DP Depression at 850 mb. Link to comment Share on other sites More sharing options...
Sunny and Warm Posted July 28, 2011 Share Posted July 28, 2011 Also of interest is the extremely low dewpoint, only 8C. what does that mean? Thanks Link to comment Share on other sites More sharing options...
Srain Posted July 28, 2011 Share Posted July 28, 2011 Obviously Don is not vertically stacked, therefore I'd be very cautious regarding track and intensity expectations until we see better alignment, if ever in the life cycle of Don. Link to comment Share on other sites More sharing options...
metalicwx366 Posted July 28, 2011 Share Posted July 28, 2011 Nice deep convection over the center now. Looks like its in its strengthening phase. Link to comment Share on other sites More sharing options...
phil882 Posted July 28, 2011 Share Posted July 28, 2011 I was about to add that. There is a nice 25°F DP Depression at 850 mb. That might explain why we saw such a lack of convection last night... dry air was very close to the circulation yesterday afternoon and it appears it got ingested last night at some point. We'll see how the convection recovers today, but it might be a fight for this little guy if those dry values stick around. I think the saving grace is that the shear vector is not from the west and that's why we should still see some intensification. That said, I might need to modify my forecast later if Don doesn't start becoming significantly better organized. Link to comment Share on other sites More sharing options...
phil882 Posted July 28, 2011 Share Posted July 28, 2011 On the positive side, the recon obs indicate that Don still has a tight wind core the maximum winds within 10 miles of the center, which means we could still see some significant strengthening if the convection can become more organized. Link to comment Share on other sites More sharing options...
wxmeddler Posted July 28, 2011 Share Posted July 28, 2011 what does that mean? Thanks Ideally, tropical cyclones should be saturated at all levels to the tropopause. By saturated I mean that that Temperature and Dew Point are the same at every level. When the temperature and dew point are not the same we call the difference (Temperature - Dew Point) the "dew point depression". The Bigger the dew point depression is at a certain level the more dry air the cyclone is ingesting at that level at that point. Dry Air can be a major factor in staving off convection and if there is enough killing at all together. Though this is hard to detect since satellites can't penetrate the higher cirrus outflow field (minus microwave imagers). Thats why we look at microwave images so much, to get a sense of the dry air. But even that doesn't tell at what level that dry is at. That's where the Hurricane Hunters and NOAA G-IV come in. Link to comment Share on other sites More sharing options...
Sunny and Warm Posted July 28, 2011 Share Posted July 28, 2011 Ideally, tropical cyclones should be saturated at all levels to the tropopause. By saturated I mean that that Temperature and Dew Point are the same at every level. When the temperature and dew point are not the same we call the difference (Temperature - Dew Point) the "dew point depression". The Bigger the dew point depression is at a certain level the more dry air the cyclone is ingesting at that level at that point. Dry Air can be a major factor in staving off convection and if there is enough killing at all together. Though this is hard to detect since satellites can't penetrate the higher cirrus outflow field (minus microwave imagers). Thats why we look at microwave images so much, to get a sense of the dry air. But even that doesn't tell at what level that dry is at. That's where the Hurricane Hunters and NOAA G-IV come in. Thank you. Yeah, I had never come across dew point depression before. I thought that's what it was, but since I'm in a science forum, there's no reason to stay in the dark. Link to comment Share on other sites More sharing options...
wxmeddler Posted July 28, 2011 Share Posted July 28, 2011 Thank you. Yeah, I had never come across dew point depression before. I thought that's what it was, but since I'm in a science forum, there's no reason to stay in the dark. No problem! It never hurts to ask. Link to comment Share on other sites More sharing options...
Srain Posted July 28, 2011 Share Posted July 28, 2011 Good morning Don... Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 28, 2011 Share Posted July 28, 2011 Aircraft now approaching Don from the North, and still an impressive lack of moisture. About that huge dewpoint depression. Natural half glass full optimist in me is hoping -70ºC topped convection is helping transfer moisture from the Gulf and low level environment into Don. Recon doesn't suggest must good happened overnight, pressure wise. Link to comment Share on other sites More sharing options...
OSUmetstud Posted July 28, 2011 Share Posted July 28, 2011 About that huge dewpoint depression. Natural half glass full optimist in me is hoping -70ºC topped convection is helping transfer moisture from the Gulf and low level environment into Don. Recon doesn't suggest must good happened overnight, pressure wise. how were the dewpoint depressions to the south and east of the system? Link to comment Share on other sites More sharing options...
am19psu Posted July 28, 2011 Share Posted July 28, 2011 how were the dewpoint depressions to the south and east of the system? North and east were 11-13C. They didn't sample the southern semicircle on the first pass. Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 28, 2011 Share Posted July 28, 2011 Vortex Message was 13ºC (21º and 8º). I'm impressed it can be firing deep convection now... Link to comment Share on other sites More sharing options...
OSUmetstud Posted July 28, 2011 Share Posted July 28, 2011 North and east were 11-13C. They didn't sample the southern semicircle on the first pass. hmm...and the shear vector is from the direction. Hopefully it improves. Link to comment Share on other sites More sharing options...
turtlehurricane Posted July 28, 2011 Share Posted July 28, 2011 Extrap 999 mb, and it appears that's even with missing the center since winds were 30 kt where that measurement was taken. With the NHC 10 kt = 1 mb rule of thumb that suggests a minimum pressure of 996 mb. Vigorous convection like we're seeing right now can do some amazing things. Link to comment Share on other sites More sharing options...
battlebrick Posted July 28, 2011 Share Posted July 28, 2011 What are the t# numbers? Link to comment Share on other sites More sharing options...
tmagan Posted July 28, 2011 Share Posted July 28, 2011 What are the t# numbers? T2.5 Link to comment Share on other sites More sharing options...
Srain Posted July 28, 2011 Share Posted July 28, 2011 What are the t# numbers? 28/1145 UTC 23.9N 89.5W T2.5/2.5 DON Link to comment Share on other sites More sharing options...
metalicwx366 Posted July 28, 2011 Share Posted July 28, 2011 Could someone please explain what are t# numbers and extrapolated pressure and what they are used for? Thanks Link to comment Share on other sites More sharing options...
phil882 Posted July 28, 2011 Share Posted July 28, 2011 Based on SFMR obs. The winds will likely be increased to at least 40 knots on the next advisory. Link to comment Share on other sites More sharing options...
Master of Disaster Posted July 28, 2011 Share Posted July 28, 2011 Could someone please explain what are t# numbers and extrapolated pressure and what they are used for? Thanks Dvorak technique. Link to comment Share on other sites More sharing options...
Srain Posted July 28, 2011 Share Posted July 28, 2011 Product: Air Force Vortex Message (URNT12 KNHC) Transmitted: 28th day of the month at 14:22Z Corrected: This observation corrected a previous observation. Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303) Storm Number & Year: 04L in 2011 Storm Name: Don (flight in the North Atlantic basin) Mission Number: 2 Observation Number: 07 A. Time of Center Fix: 28th day of the month at 13:50:10Z B. Center Fix Coordinates: 23°59'N 89°55'W (23.9833N 89.9167W) B. Center Fix Location: 414 miles (667 km) to the S (179°) from New Orleans, LA, USA. C. Minimum Height at Standard Level: 1,442m (4,731ft) at 850mb D. Estimated (by SFMR or visually) Maximum Surface Wind: 29kts (~ 33.4mph) E. Location of the Estimated Maximum Surface Wind: 2 nautical miles (2 statute miles) to the SSW (201°) of center fix F. Maximum Flight Level Wind Inbound: From 81° at 32kts (From the E at ~ 36.8mph) G. Location of Maximum Flight Level Wind Inbound: 2 nautical miles (2 statute miles) to the NNW (346°) of center fix H. Minimum Sea Level Pressure: 1001mb (29.56 inHg) - Extrapolated I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 18°C (64°F) at a pressure alt. of 1,523m (4,997ft) J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 26°C (79°F) at a pressure alt. of 1,515m (4,970ft) K. Dewpoint Temp (collected at same location as temp inside eye): 8°C (46°F) K. Sea Surface Temp (collected at same location as temp inside eye): Not Available L. Eye Character: Not Available M. Eye Shape: Not Available N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature N. Fix Levels (sfc and flt lvl centers are within 5nm of each other): Surface and 850mb O. Navigation Fix Accuracy: 0.02 nautical miles O. Meteorological Accuracy: 1.5 nautical miles Remarks Section - Remarks That Were Decoded... Maximum Flight Level Wind: 52kts (~ 59.8mph) in the east quadrant at 11:57:10Z Maximum Flight Level Wind Outbound: 38kts (~ 43.7mph) in the southeast quadrant at 14:15:50Z Sea Level Pressure Extrapolation From: 850mb Remarks Section - Additional Remarks... EYE SONDE MEASURED 1004MB WITH 17 KTS SFC WIND FEEDERBAND CROSSING SE OUTBOUND LEG 70 NM SE OF CTR COR FOR MAX OUTBOUND FL WIND IN CONVECTIVE BAND Link to comment Share on other sites More sharing options...
phil882 Posted July 28, 2011 Share Posted July 28, 2011 Could someone please explain what are t# numbers and extrapolated pressure and what they are used for? Thanks Extrapolated pressure is simpily the surface estimated pressure from aircraft. This uses a general equation (hipsometric for math buffs) that is reasonably accurate but extrapolated down from the elevation of the aircraft. This is generally considered less accurate however than direct observations from dropsondes. Link to comment Share on other sites More sharing options...
David Reimer Posted July 28, 2011 Share Posted July 28, 2011 We'll most likely get Tropical Storm Warnings issued with the 11 AM package. Link to comment Share on other sites More sharing options...
Srain Posted July 28, 2011 Share Posted July 28, 2011 TS Warnings hoisted from Port Mansfield to San Luis Pass Texas...Don is a bit stronger as well... BULLETIN TROPICAL STORM DON ADVISORY NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042011 1000 AM CDT THU JUL 28 2011 ...HURRICANE HUNTER AIRCRAFT FINDS THAT DON IS A LITTLE STRONGER... SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...24.1N 90.1W ABOUT 520 MI...840 KM ESE OF CORPUS CHRISTI TEXAS ABOUT 480 MI...770 KM ESE OF BROWNSVILLE TEXAS MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H PRESENT MOVEMENT...NW OR 305 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...1001 MB...29.56 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY... A TROPICAL STORM WARNING IS NOW IN EFFECT FOR THE TEXAS COAST FROM PORT MANSFIELD TO SAN LUIS PASS. SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A TROPICAL STORM WARNING IS IN EFFECT FOR... * TEXAS COAST FROM PORT MANSFIELD TO SAN LUIS PASS A TROPICAL STORM WATCH IS IN EFFECT FOR... * TEXAS COAST SOUTH OF PORT MANSFIELD TO THE MOUTH OF THE RIO GRANDE A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS. A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS. FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ AT 1000 AM CDT...1500 UTC...THE CENTER OF TROPICAL STORM DON WAS LOCATED NEAR LATITUDE 24.1 NORTH...LONGITUDE 90.1 WEST. DON IS MOVING TOWARD THE NORTHWEST NEAR 14 MPH...22 KM/H. A GENERAL MOTION TOWARD THE NORTHWEST OR WEST-NORTHWEST IS EXPECTED THROUGH SATURDAY. ON THIS TRACK...THE CENTER OF DON SHOULD CROSS THE CENTRAL GULF OF MEXICO TODAY...APPROACH THE TEXAS COAST ON FRIDAY....AND REACH THE TEXAS COAST FRIDAY NIGHT OR SATURDAY. MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER GUSTS. GRADUAL STRENGTHENING IS FORECAST DURING THE NEXT 36 HOURS. TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 60 MILES...95 KM FROM THE CENTER. A MEXICAN AUTOMATED STATION AT ISLA PEREZ IN THE GULF OF MEXICO RECENTLY REPORTED A WIND GUST OF 38 MPH...61 KM/H. THE MINIMUM CENTRAL PRESSURE EXTRAPOLATED BY THE HURRICANE HUNTER AIRCRAFT IS 1001 MB...29.56 INCHES. HAZARDS AFFECTING LAND ---------------------- WIND...TROPICAL STORM CONDITIONS ARE EXPECTED WITHIN THE WARNING AREA BY LATE FRIDAY OR FRIDAY NIGHT. TROPICAL STORM CONDITIONS ARE POSSIBLE IN THE WATCH AREA BY LATE FRIDAY OR FRIDAY NIGHT. STORM SURGE...A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 1 TO 2 FEET ABOVE GROUND LEVEL...MAINLY ALONG THE IMMEDIATE COAST NEAR AND TO THE NORTHEAST OF WHERE THE CENTER MAKES LANDFALL. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE AND DAMAGING WAVES. RAINFALL...DON IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS OF 3 TO 5 INCHES FROM THE CENTRAL TEXAS COAST WESTWARD INTO SOUTH CENTRAL TEXAS...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 7 INCHES. NEXT ADVISORY ------------- NEXT INTERMEDIATE ADVISORY...100 PM CDT. NEXT COMPLETE ADVISORY...400 PM CDT. $$ FORECASTER BEVEN Link to comment Share on other sites More sharing options...
Ed Lizard Posted July 28, 2011 Share Posted July 28, 2011 18º dewpoint depression. And its still putting up -70ºC towers. Link to comment Share on other sites More sharing options...
battlebrick Posted July 28, 2011 Share Posted July 28, 2011 3 to 5 in of rain.. I guess thats good for Texas. Link to comment Share on other sites More sharing options...
phil882 Posted July 28, 2011 Share Posted July 28, 2011 Microwave shows a mainly exposed center. Link to comment Share on other sites More sharing options...
Juliancolton Posted July 28, 2011 Share Posted July 28, 2011 I initially thought this had high-end Cat 2 potential, but it's still a relatively disorganized system, and I'd put 65 kts as the ceiling for intensification before landfall now. Link to comment Share on other sites More sharing options...
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