WEATHERAmerica Newsletter, Friday, April 21, 2006 at 3:35 A.M. ET
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WEATHER SUMMARY THROUGH NEXT 72
HOURS
This spring that seems to be pointing toward widespread drought over the Dixie states and the Eastern Seaboard, but events over the next few days indicate a dent in the heretofore uneventful 500MB longwave pattern. The huge cutoff low in the Upper Midwest (that dumped all kinds of wet snow in the Black Hills vicinity about 48 hours ago) is linking with a southern branch system moving out of N TX and OK. Since the lower latitude feature has drawn in a fetch of high dewpoints, surface low pressure developing in the phasing between the two systems will have abundant moisture to work with. So instead of the very dry, warm scenario seen across the Old South and Atlantic Coastal Plain, an impressive rainfall event may be shaping up, accompanied by severe weather.
The thunderstorm potential is greatest this afternoon and evening from the Ohio Valley to the central Gulf Coast. One area of convection may form with the "triple point" of the older northern branch low, currently nearing Cincinnati OH. Another will arise in LA....MS....AL, then track northeastward with the formative low as it crosses the Cumberland Plateau. While not in the same leagues as the severe weather outbreaks seen earlier this month, convection that fires today (and again on Saturday through the Southeast into VA) will develop in fairly unstable air, so that microbursts and hail reports will not be uncommon.
When the emerging low reaches the Mid-Atlantic region on Saturday night, the orientation of the upper system and position with respect to an oceanic high pressure cell will favor a deep mean flow of moisture from both the western Atlantic Ocean and the Caribbean Sea. A linear banding of extremely strong upward motion should form, sparking a convective+overrunning rainfall event that progresses from the Chesapeake Bay/Susquehanna River watershed into southern New England. 1-3 inch rainfall amounts will go a long way toward easing drought and fire hazards. The 500MB component should also spawn a secondary surface low, perhaps prolonging rainfall chances in the coastal Northeast early next week.
Another southern branch system is predicted to pass through CA and the Great Basin, undercutting a Rex block in western and central Canada. Due to the blocking configuration and the couplet of disturbances downstream, the forward motion of the newer low will be very gradual, probably reaching the "Four Corners" vicinity on Day 3. Interestingly, both the 0z Apr 21 GFS and NAM depictions show a mesoscale convective complex racing out ahead of the main feature into the central Great Plains by 72 hours. While this is plausible due to the very volatile baroclinic zone (hot in TX and OK, relatively cool KS and MO), moisture may well be an issue with the mTw advection occurring along the East Coast.
Short-Range Numerical Weather
Prediction Models
(red dot
indicates preferred model)
______________________________________________________________________
RUC NAM. GFS-5 RGEM. MM5 UKMET
CRAS SREF COAMPS RAMS
The
Weather Research And Forecasting Model Website
National Centers for Environmental
Prediction Models
Texas A&M Weather
Interface
______________________________________________________________________
Online Weather Discussions And
Forums
U.S. & World Weather Forums
CanadianWeather.org - Forecasts, Charts and Community
Forums
Online Weather Information
Guides
AMS Glossary WW2010 Helper Section
Index
Weather Calculator
COMET Case Study Library on the WWW
Climate Normals For The U.S.
Golden Gate Weather ENSO
Page
Weather Information
Plotting/Mapping
nowCOAST: GIS Mapping
Portal
NOAA Internal Experimental Winter Weather Impact
Graphics
The Weather Forecaster Web
Page
Plymouth State Weather
Center
Dr. Bob Hart's
Coolwx.com
U.S.
National Satellite Perspectives
Next-Generation Weather Satellite Demonstration
Project
Infrared Visible Vapor
Hawaii Infrared Hawaii Visible
Alaska Infrared Alaska Visible Alaska
Vapor
Canada Satellite
Perspectives
Environment Canada Satellite Image
Directory
Satellite Animations And
Multi-Channel Imagery
RAMSDIS ONLINE
NOAA Polar Satellite
Views Around North America
Quicklook Swaths
Browser
AVHRR Dynamic Tracking Windows
Milan Konecny's NOAA Satellite Views
Savannah-Weather.Com
NOAA HRPT Weather Satellite Images
National Radar
Summaries
National NEXRAD Summary
Environment Canada Radar
Summary
Numerical Model Temperature
Forecasts
Current NWS MOS Forecast
Products
Links To Current Weather Conditions
Around
North America And Worldwide
MesoNet Data
NWS Precipitation Analysis
Pages Current Weather Observations
Ocean Prediction Center - Unified Surface
Analysis
National Data Buoy Center Near Real-Time Polar
Products
Solar, Lunar, Astronomy
Information
MeL: Space &
Astronomy
SpaceWeather.Com
Tonight's Sky Sky & Telescope Interactive Sky
Chart
Human Space Flight - NASA-TV Solar
Terrestrial Activity Report
Satellite-Derived Forecast Products
NOAA/NESDIS/ORA
Forecast Products
Near Real-Time Polar
Products
Upper Air Analyses
Around North America
Upper Air Data From University Of
Wyoming
Aviation Weather
Analyses And Forecasts
Soundings from Commercial
Airliners
Aviation Weather Center
(AWC)
ORA Projects Page
ADDS - Turbulence
Environment Canada Aviation
Products
National Soil
Moisture Levels
Palmer Index Map (For Soil Moisture)
Drought Monitor
___________________________________________________________________________
SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging
winds, and large hail within the next 24 hours)
HEAVY RAINFALL OUTLOOK
(potential for an inch or more
total rainfall within the next 24 hours)
(probable trajectory for midlatitude cyclones affecting populous sections of the United States and Canada)
______________________________________________________________________
AWC National Convective Weather Forecast Product
Oklahoma University Daily Real Time Analysis And Forecast System
Experimental 0-3 Hour Convective Weather Forecast Products
Collaborative Convective Forecast Product
Environment Canada Severe Weather Model
Severe Weather Watch Boxes
SPC Watch, Warning and Advisory Display
Local Weather Warnings
College Of DuPage Severe Weather Warnings Page
U.S. Station Weather Probability Forecasts
READY - State Weather
NAM MOS Graphics NGM MOS Graphics
Form For Selecting AVN MOS Bulletins NAM Precip Type Meteograms
______________________________________________________________________
Visible, Infrared, And Water Vapor
High Resolution Satellite And Radar Views:
University Of Washington Weather Graphics Loops
IPS Meteostar
Regional Radar Summaries
Northeast
Southeast
North Central
South Central
Northwest
Southwest
Useful
Television Station And Commercial
Doppler Radar Sites
WeatherMatrix Radar Supersite : TV
Radars
Doppler Radar Images From Government Sources
National Weather Service Doppler
Radars
Environment Canada Doppler
Radars
Experimental
Radar Images From The National Weather Service
National
Lightning Detection Map
StrikeStar US
Experimental Lightning Location
Network
Environment Canada Lightning
Map
BARBADOS Worthing VIRGIN ISLANDS St. Croix
Media Resources, Online Mapping And Travel AidsKevin Brewster Storm Spotting Frequencies Page
TV Station Web Page Directory Radio-Locator
National Traffic and Road Closure Information Traffic Reports Gas Prices MapQuest Windows Live Local Microsoft TerraServer Google Earth
The National Atlas of the United States of America
Where On Earth - Latitude Longitude Finder
Map-It - A GMT3 Map Generator
MEDIUM RANGE OUTLOOK
(weather trends through the next
6 to 10 days)
The evolution of
a long-lasting Rex block across western Canada, unforeseen by earlier computer
forecasts, will have a pronounced effect on apparent weather across the lower 48
states. A first consideration is the slowing of an upper level low in the
Northeast, which may keep moderate stratiform rains in place across parts of
coastal New England into NS into Wednesday. That disturbance will merge with a
much colder and stronger 500MB low in QC, creating a trough which should help to
advect very cool and dry air into the Great Lakes and Appalachia on Day
5.
There is also the matter of the low and frontal structure crossing through the middle and lower Intermountain Region. While I think the speed of convection is exaggerated by the most recent GFS panels (and the concurrent run of the ECMWF wrongly flattens the emerging energy), the solution offered by the 0z Apr 21 GGEM scheme seems logical. The low and trough will probably reach the Great Plains on April 25/26, with capping eliminating thunderstorm potential south of Interstate 40. N OK....N AR....W, C MO....KS....S NE, however, could see a prolonged outbreak of severe weather and heavy rain. By 120-144 hours, interaction with the eastern Canada trough complex may allow for the Corn Belt and Mid-South to be targeted by the convective event. Leftover energy, with mainly moderate rainfall, will pass through the Northeast around April 27-28.
If the blocking pattern holds, expect more energy to dig under the ridge in AB and BC. This would mean another unseasonable dose of rain and thunder for CA and the Southwest beyond 168 hours, with the activity moving into the Great Plains and Midwest by May 1. Cooler values holding through the Great Lakes and Northeast at that time (with heat and humidity prevalent in Dixie) may favor the low taking a more southward track, close to the Ohio River and Mason-Dixon line by Day 10.
Medium Range Numerical Weather Prediction
Models
(red dot indicates preferred model)
______________________________________________________________________
GFS UKMETx ECMWF NOGAPS GGEM. MM5x KMA RSM JMA CPTEC GBL Ensembles DGEX EPS Maps
NCEP AVN-GFS
Ensembles NOGAPS Ensembles WRF Hemispheric
Medium Range NWP Verification
Statistics
Climate Prediction Center - D+8 Upper Air
Tools
______________________________________________________________________
Worldwide and International Satellite
Images
Earth Viewer: View Any Location from Any
Satellite
______________________________________________________
GOES 12 (The
Americas, Atlantic Ocean)
Visible Infrared Vapor
______________________________________________________
GOES 10 (Eastern
Pacific Ocean)
Visible Infrared Vapor
______________________________________________________
GMS 5 (Asia,
Australia, Pacific Ocean)
Visible Infrared Vapor
______________________________________________________
METEOSAT 5
(Central Asia)
Visible Infrared Vapor
______________________________________________________
METEOSAT 7
(Europe And Africa)
Visible Infrared Vapor
______________________________________________________
Arctic Sea
Europe Infrared Europe Visible Europe Vapor
Russia The Middle East The Orient India
Australia New Zealand South America Africa
Antarctica
______________________________________________________________________
International Weather Radar Sites
WeatherMatrix Radar Supersite : World Radar
Data
Domestic And
International Weather Cameras
EarthCam
- Webcam Network
Satellite Images Of Individual Tropical
Systems
NRL Monterey Tropical Cyclone
Page
QuikSCAT
Satellite Images Of
Tropical Regions
GHCC - Interactive GOES-8 Infrared Hurricane
Sector
Atlantic Basin Satellite Services Division - Tropical Atlantic Satellite
Imagery
Mexico And Pacific Coastal
Waters
Central Pacific Ocean
Oceania And Tropical Western Pacific
Ocean
Indian Ocean
Digital Typhoon:
Typhoon Images and Information
Sea
Surface Temperatures
NODC Coastal Water Temperature
Guide
Great
Lakes Sea Grant Coastwatch Homepage
NCODA Sea Surface
Temperatures
NCODA Sea Surface Temperature
Anomaly
NCODA Sea Surface Temperature
Climatology
Marine Weather
Information
WWW Tide/Current Predictor - Site
Selection
Office of Coast Survey - Home - Nautical
Charts
Regional Ocean Forecast System
(ROFS)
NOAA/NCEP WAM Global Swell
Data
Environment Canada Ocean Wave
Forecasts
NOAA WAVEWATCH III Wave Models
(interactive)
Great Lakes Water
Levels
Prepared by Meteorologist LARRY COSGROVE
on
Friday, April 21, 2006 at 3:35 A.M. ET
Disclaimer:
The previous statements are my opinions only,
and should not be construed as definitive fact. Links provided on this
newsletter are not affiliated with WEATHERAmerica and
the publisher is not responsible for content posted or associated with those
sites.
Copyright 2006 by Larry Cosgrove
All rights
reserved.
This publication may not be reproduced or redistributed in
whole or in part without the expressed written consent of the
author.