Skip Navigation Links weather.gov   
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
National Hurricane Center
Local forecast by
"City, St" or "ZIP"

 
Alternate Formats
   Text     |   Mobile
   Email   |   RSS XML/RSS logo
   About Alternates
Cyclone Forecasts
   Latest Advisory
   Past Advisories
   Audio/Podcasts
   About Advisories
Marine Forecasts
   Atlantic & E Pacific
   Gridded Marine
   About Marine
Tools & Data
   Satellite | Radar
   Analysis Tools
   Aircraft Recon
   GIS Datasets
   Data Archive
Development
   Experimental
   Research
   Forecast Accuracy
Outreach & Education
   Prepare
   Storm Surge
   About Cyclones
   Cyclone Names
   Wind Scale
   Most Extreme
   Forecast Models
   Breakpoints
   Resources
   Glossary | Acronyms
   Frequent Questions
Our Organization
   About NHC
   Mission & Vision
   Staff | Q&A
   Visitors | Virtual Tour
   Library Branch
   NCEP | Newsletter
Contact Us
   Comments
Follow the National Hurricane Center on Facebook Follow the National Hurricane Center on Twitter
Subscribe the National Hurricane Center on YouTube Read the National Hurricane Center Inside the Eye blog on WordPress
FirstGov.gov is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.
 
 

Tropical Storm IRWIN


ZCZC MIATCDEP1 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM IRWIN DISCUSSION NUMBER  36
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112011
800 PM PDT FRI OCT 14 2011
 
THE LAST FEW VISIBLE IMAGES OF THE DAY SHOWED LOW CLOUDS IN THE
SOUTHEASTERN QUADRANT OF IRWIN MOVING EASTWARD TOWARDS THE MEXICAN
COAST...INSTEAD OF TURNING CYCLONICALLY AROUND THE CENTER.  THIS
FLOW PATTERN IS LIKELY PRODUCING LOW-LEVEL DIVERGENCE...WHICH BY
ITSELF WOULD NOT BE SUPPORTIVE OF CONVECTIVE DEVELOPMENT.  AS A
POSSIBLE CONSEQUENCE...MUCH OF THE DEEP CONVECTION THAT DEVELOPED
WITH IRWIN EARLIER IN THE DAY HAS EVAPORATED.  CURRENT INTENSITY
ESTIMATES FROM TAFB...SAB...AND THE UW-CIMSS ADT RANGE FROM 30 TO
50 KT...SO THE INITIAL INTENSITY IS MAINTAINED AT 40 KT.

THE LOW-LEVEL CENTER BECAME A LITTLE MORE APPARENT JUST BEFORE
SUNSET...AND WITH THE SUPPORT OF MICROWAVE DATA...IRWIN IS
ESTIMATED TO BE MOVING SOUTH-SOUTHEASTWARD WITH A 12-HR MOTION OF
165/6 KT.  A MID-LEVEL HIGH OVER NORTHWESTERN MEXICO IS EXPECTED TO
EXPAND SOUTHWESTWARD OVER THE NEXT FEW DAYS AND SHOULD CAUSE IRWIN
TO TURN SOUTHWARD SOON AND WESTWARD BY 48 HOURS.  THEREAFTER...BROAD
LOW/MID-LEVEL CYCLONIC FLOW NEAR CENTRAL AMERICA IS FORECAST TO
DRIFT WESTWARD JUST FAR ENOUGH TO CAUSE IRWIN TO SLOW DOWN AND MOVE
ERRATICALLY.  MOST OF THE TRACK GUIDANCE AGREES ON THIS SCENARIO
AND EVEN SUGGEST THAT IRWIN COULD BECOME NEARLY STATIONARY ON DAY 4
AND TURN BACK TO THE SOUTHEAST BY DAY 5.  THE NEW OFFICIAL FORECAST
HAS BEEN SHIFTED A LITTLE TO THE SOUTH AND WEST ON DAYS 4 AND 5 BUT
IS OTHERWISE VERY SIMILAR TO THE PREVIOUS FORECAST.

THE FORECAST TRACK TAKES IRWIN THROUGH A MARGINAL ENVIRONMENT FOR
INTENSIFICATION DURING THE NEXT FEW DAYS.  NEGATIVE FACTORS INCLUDE
INCREASING VERTICAL SHEAR...THE COLD OCEANIC WAKE LEFT BY HURRICANE
JOVA...A DRY ENVIRONMENTAL AIR MASS...AND THE AFOREMENTIONED
LOW-LEVEL DIVERGENCE.  HOWEVER AS IRWIN MOVES SOUTHWARD AWAY FROM
MEXICO...IT WILL BE MOVING INTO A MOISTER AIR MASS...AND LOW-LEVEL
CONVERGENCE SHOULD BE ABLE TO INCREASE.  THESE FACTORS COULD FOSTER
RE-DEVELOPMENT OF DEEP CONVECTION.  GIVEN THE CONFLICTING
SIGNALS...THE OFFICIAL FORECAST CONTINUES TO HOLD THE INTENSITY
STEADY FOR THE FIRST 3 DAYS...FOLLOWED BY GRADUAL WEAKENING AND
TRANSITION TO A REMNANT LOW.  IT SHOULD BE NOTED THAT NEARLY ALL OF
THE INTENSITY MODELS INDICATE SOME STRENGTHENING DURING THE NEXT
COUPLE OF DAYS AND IS ANOTHER REASON TO NOT SHOW WEAKENING DURING
THE FIRST PART OF THE FORECAST PERIOD.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/0300Z 17.7N 106.4W   40 KT  45 MPH
 12H  15/1200Z 16.8N 106.7W   40 KT  45 MPH
 24H  16/0000Z 15.6N 107.2W   40 KT  45 MPH
 36H  16/1200Z 14.8N 108.0W   40 KT  45 MPH
 48H  17/0000Z 14.5N 108.9W   40 KT  45 MPH
 72H  18/0000Z 15.0N 110.0W   40 KT  45 MPH
 96H  19/0000Z 15.0N 110.5W   30 KT  35 MPH
120H  20/0000Z 14.5N 110.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BERG
 
NNNN


Quick Navigation Links:
Tropical Cyclone Forecasts  -  Tropical Marine Forecasts  -  Data Archive
Outreach  -  Prepare  -  About Cyclones  -  About NHC  -  Contact Us

NOAA/ National Weather Service
National Centers for Environmental Prediction
National Hurricane Center
11691 SW 17th Street
Miami, Florida 33165-2149 USA
nhcwebmaster@noaa.gov
Disclaimer
Credits
Information Quality
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities
Page last modified: Tuesday, 17-Jul-2012 13:44:20 UTC