Caribbean-On-Line's Caribbean Hurricane Blog



HURRICANE OMAR DISCUSSION NUMBER 9

Published on October 15, 2008 11:17 AM | Comments

HURRICANE OMAR DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL152008 1100 AM EDT WED OCT 15 2008

ON ITS FINAL LEG AROUND 11Z...AN AIR FORCE HURRICANE HUNTER AIRCRAFT REPORTED A PEAK SFMR SURFACE WIND OF 70 KT IN THE NORTHWEST QUADRANT OF OMAR'S EYEWALL. THIS WAS COINCIDENT WITH A NEARBY DROPSONDE SURFACE WIND VALUE OF 68 KT...SO THE INTENSITY AT THE 12Z SYNOPTIC TIME WAS INCREASED TO 70 KT. HOWEVER...SINCE THE LAST RECON FLIGHT...THE EYE HAS BECOME EVIDENT IN VISIBLE SATELLITE IMAGERY...AND ALSO IN THE SAN JUAN DOPPLER WEATHER RADAR DATA AT A RANGE OF MORE THAN 200 NMI. SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS T4.5/77 KT FROM TAFB AND SAB...SO THE ADVISORY INTENSITY HAS BEEN INCREASED TO 75 KT BASED ON THE IMPROVED SATELLITE AND RADAR SIGNATURES.

THE INITIAL MOTION ESTIMATE IS 045/08. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS TRACK FORECAST OR PHILOSOPHY. OMAR IS BASICALLY ON THE PREVIOUS ADVISORY TRACK...AND THE NHC MODEL GUIDANCE REMAINS TIGHTLY CLUSTERED ABOUT A NORTHEASTWARD MOTION THROUGH THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS IN ABOUT 24 HOURS. AFTER THAT...OMAR IS EXPECTED TO ACCELERATE AS IT GETS CAUGHT UP IN THE STRONG SOUTHWESTERLY FLOW ON THE EAST SIDE OF A LARGE DEEPENING MID-TROPOSPHERIC TROUGH LOCATED OVER THE WESTERN ATLANTIC. A PIECE OF THE TROUGH BREAKS OFF AND LIFTS OUT TO THE NORTHEAST IN 72-96 HOURS...WHICH BRIEFLY WEAKENS THE STEERING FLOW. AFTER THAT...HOWEVER...THE MID-LATITUDE WESTERLIES ARE FORECAST TO INCREASE AHEAD OF A STRONGER LOW PRESSURE SYSTEM...WHICH IS EXPECTED TO ACCELERATE OMAR TO THE EAST-NORTHEAST AT 35-40 KT. THE OFFICIAL FORECAST TRACK WAS NUDGED A LITTLE TO THE LEFT OF THE PREVIOUS TRACK AND REMAINS SLOWER THAN THE NHC MODEL CONSENSUS.

NOW THAT A DISTINCT EYE AND EYEWALL HAVE DEVELOPED...A GOOD CHIMNEY EFFECT CAN BE ESTABLISHED AND OMAR COULD GO THROUGH A BRIEF PERIOD OF RAPID INTENSIFICATION AGAIN. ONLY THE GFDL MODEL IS CALLING FOR OMAR TO STRENGTHEN TO AT LEAST 90 KT. THE REMAINDER OF THE INTENSITY GUIDANCE HOLDS OMAR BELOW 80 KT. BASED ON THE BETTER DEFINED EYE FEATURE...AND THE FACT THAT OMAR IS A RELATIVELY LOW SHEAR ENVIRONMENT AND OVER 29C AND WARMER SSTS...ADDITIONAL INTENSIFICATION SIMILAR TO THE GFDL MODEL SEEMS QUITE REASONABLE. IT ALSO ISN'T OUT OF THE QUESTION THAT OMAR COULD ACHIEVE MAJOR HURRICANE STATUS JUST BEFORE THE CYCLONE REACHES THE NORTHERN LEEWARD ISLANDS. HOWEVER...THE RAPID ENCROACHMENT OF DRY MID-LEVEL AIR FROM THE NORTHWEST AS NOTED IN WATER VAPOR SATELLITE IMAGERY PRECLUDES EXPLICITLY FORECASTING THAT INTENSITY AT THIS TIME SINCE THAT DRY AIR COULD MAKE IT INTO THE INNER CORE REGION IN 12-18 HOURS AND WEAKEN THE HURRICANE.

ALTHOUGH THE OFFICIAL FORECAST KEEPS THE CENTER EAST OF PUERTO RICO...ONLY A SLIGHT DEVIATION TO THE LEFT OF THE CURRENT MOTION COULD REQUIRE CHANGING THE HURRICANE WATCH TO A HURRICANE WARNING FOR THAT ISLAND. ALSO...STRONGER WINDS...POSSIBLY ONE CATEGORY HIGHER...CAN BE EXPECTED OVER HIGHER TERRAIN...ESPECIALLY ABOVE 500 FT ELEVATION.



comments powered by Disqus